settings.c

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/*
 * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <byteswap.h>
#include <errno.h>
#include <assert.h>
#include <time.h>
#include <ipxe/in.h>
#include <ipxe/ip.h>
#include <ipxe/ipv6.h>
#include <ipxe/vsprintf.h>
#include <ipxe/dhcp.h>
#include <ipxe/uuid.h>
#include <ipxe/uri.h>
#include <ipxe/base16.h>
#include <ipxe/base64.h>
#include <ipxe/pci.h>
#include <ipxe/init.h>
#include <ipxe/version.h>
#include <ipxe/settings.h>

/** @file
 *
 * Configuration settings
 *
 */

/******************************************************************************
 *
 * Generic settings blocks
 *
 ******************************************************************************
 */

/**
 * A generic setting
 *
 */
struct generic_setting {
        /** List of generic settings */
        struct list_head list;
        /** Setting */
        struct setting setting;
        /** Size of setting name */
        size_t name_len;
        /** Size of setting data */
        size_t data_len;
};

/**
 * Get generic setting name
 *
 * @v generic           Generic setting
 * @ret name            Generic setting name
 */
static inline void * generic_setting_name ( struct generic_setting *generic ) {
        return ( ( ( void * ) generic ) + sizeof ( *generic ) );
}

/**
 * Get generic setting data
 *
 * @v generic           Generic setting
 * @ret data            Generic setting data
 */
static inline void * generic_setting_data ( struct generic_setting *generic ) {
        return ( ( ( void * ) generic ) + sizeof ( *generic ) +
                 generic->name_len );
}

/**
 * Find generic setting
 *
 * @v generics          Generic settings block
 * @v setting           Setting to find
 * @ret generic         Generic setting, or NULL
 */
static struct generic_setting *
find_generic_setting ( struct generic_settings *generics,
                       const struct setting *setting ) {
        struct generic_setting *generic;

        list_for_each_entry ( generic, &generics->list, list ) {
                if ( setting_cmp ( &generic->setting, setting ) == 0 )
                        return generic;
        }
        return NULL;
}

/**
 * Store value of generic setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v data              Setting data, or NULL to clear setting
 * @v len               Length of setting data
 * @ret rc              Return status code
 */
int generic_settings_store ( struct settings *settings,
                             const struct setting *setting,
                             const void *data, size_t len ) {
        struct generic_settings *generics =
                container_of ( settings, struct generic_settings, settings );
        struct generic_setting *old;
        struct generic_setting *new = NULL;
        size_t name_len;

        /* Identify existing generic setting, if any */
        old = find_generic_setting ( generics, setting );

        /* Create new generic setting, if required */
        if ( len ) {
                /* Allocate new generic setting */
                name_len = ( strlen ( setting->name ) + 1 );
                new = zalloc ( sizeof ( *new ) + name_len + len );
                if ( ! new )
                        return -ENOMEM;

                /* Populate new generic setting */
                new->name_len = name_len;
                new->data_len = len;
                memcpy ( &new->setting, setting, sizeof ( new->setting ) );
                new->setting.name = generic_setting_name ( new );
                memcpy ( generic_setting_name ( new ),
                         setting->name, name_len );
                memcpy ( generic_setting_data ( new ), data, len );
        }

        /* Delete existing generic setting, if any */
        if ( old ) {
                list_del ( &old->list );
                free ( old );
        }

        /* Add new setting to list, if any */
        if ( new )
                list_add ( &new->list, &generics->list );

        return 0;
}

/**
 * Fetch value of generic setting
 *
 * @v settings          Settings block
 * @v setting           Setting to fetch
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
int generic_settings_fetch ( struct settings *settings,
                             struct setting *setting,
                             void *data, size_t len ) {
        struct generic_settings *generics =
                container_of ( settings, struct generic_settings, settings );
        struct generic_setting *generic;

        /* Find generic setting */
        generic = find_generic_setting ( generics, setting );
        if ( ! generic )
                return -ENOENT;

        /* Copy out generic setting data */
        if ( len > generic->data_len )
                len = generic->data_len;
        memcpy ( data, generic_setting_data ( generic ), len );

        /* Set setting type, if not yet specified */
        if ( ! setting->type )
                setting->type = generic->setting.type;

        return generic->data_len;
}

/**
 * Clear generic settings block
 *
 * @v settings          Settings block
 */
void generic_settings_clear ( struct settings *settings ) {
        struct generic_settings *generics =
                container_of ( settings, struct generic_settings, settings );
        struct generic_setting *generic;
        struct generic_setting *tmp;

        list_for_each_entry_safe ( generic, tmp, &generics->list, list ) {
                list_del ( &generic->list );
                free ( generic );
        }
        assert ( list_empty ( &generics->list ) );
}

/** Generic settings operations */
struct settings_operations generic_settings_operations = {
        .store = generic_settings_store,
        .fetch = generic_settings_fetch,
        .clear = generic_settings_clear,
};

/******************************************************************************
 *
 * Registered settings blocks
 *
 ******************************************************************************
 */

/** Root generic settings block */
struct generic_settings generic_settings_root = {
        .settings = {
                .refcnt = NULL,
                .name = "",
                .siblings =
                    LIST_HEAD_INIT ( generic_settings_root.settings.siblings ),
                .children =
                    LIST_HEAD_INIT ( generic_settings_root.settings.children ),
                .op = &generic_settings_operations,
        },
        .list = LIST_HEAD_INIT ( generic_settings_root.list ),
};

/** Root settings block */
#define settings_root generic_settings_root.settings

/** Autovivified settings block */
struct autovivified_settings {
        /** Reference count */
        struct refcnt refcnt;
        /** Generic settings block */
        struct generic_settings generic;
};

/**
 * Free autovivified settings block
 *
 * @v refcnt            Reference count
 */
static void autovivified_settings_free ( struct refcnt *refcnt ) {
        struct autovivified_settings *autovivified =
                container_of ( refcnt, struct autovivified_settings, refcnt );

        generic_settings_clear ( &autovivified->generic.settings );
        free ( autovivified );
}

/**
 * Find child settings block
 *
 * @v parent            Parent settings block
 * @v name              Name within this parent
 * @ret settings        Settings block, or NULL
 */
struct settings * find_child_settings ( struct settings *parent,
                                        const char *name ) {
        struct settings *settings;

        /* Find target parent settings block */
        parent = settings_target ( parent );

        /* Treat empty name as meaning "this block" */
        if ( ! *name )
                return parent;

        /* Look for child with matching name */
        list_for_each_entry ( settings, &parent->children, siblings ) {
                if ( strcmp ( settings->name, name ) == 0 )
                        return settings_target ( settings );
        }

        return NULL;
}

/**
 * Find or create child settings block
 *
 * @v parent            Parent settings block
 * @v name              Name within this parent
 * @ret settings        Settings block, or NULL
 */
struct settings * autovivify_child_settings ( struct settings *parent,
                                              const char *name ) {
        struct {
                struct autovivified_settings autovivified;
                char name[ strlen ( name ) + 1 /* NUL */ ];
        } *new_child;
        struct settings *settings;

        /* Find target parent settings block */
        parent = settings_target ( parent );

        /* Return existing settings, if existent */
        if ( ( settings = find_child_settings ( parent, name ) ) != NULL )
                return settings;

        /* Create new generic settings block */
        new_child = zalloc ( sizeof ( *new_child ) );
        if ( ! new_child ) {
                DBGC ( parent, "Settings %p could not create child %s\n",
                       parent, name );
                return NULL;
        }
        memcpy ( new_child->name, name, sizeof ( new_child->name ) );
        ref_init ( &new_child->autovivified.refcnt,
                   autovivified_settings_free );
        generic_settings_init ( &new_child->autovivified.generic,
                                &new_child->autovivified.refcnt );
        settings = &new_child->autovivified.generic.settings;
        register_settings ( settings, parent, new_child->name );
        ref_put ( settings->refcnt );
        return settings;
}

/**
 * Return settings block name
 *
 * @v settings          Settings block
 * @ret name            Settings block name
 */
const char * settings_name ( struct settings *settings ) {
        static char buf[16];
        char tmp[ 1 /* '.' */ + sizeof ( buf ) ];

        /* Find target settings block */
        settings = settings_target ( settings );

        /* Construct name */
        buf[0] = '\0';
        tmp[0] = '\0';
        for ( ; settings->parent ; settings = settings->parent ) {
                memcpy ( ( tmp + 1 ), buf, ( sizeof ( tmp ) - 1 ) );
                snprintf ( buf, sizeof ( buf ), "%s%s", settings->name, tmp );
                tmp[0] = '.';
        }
        return buf;
}

/**
 * Parse settings block name
 *
 * @v name              Name
 * @v get_child         Function to find or create child settings block
 * @ret settings        Settings block, or NULL
 */
static struct settings *
parse_settings_name ( const char *name, get_child_settings_t get_child ) {
        struct settings *settings = &settings_root;
        char *name_copy;
        char *subname;
        char *remainder;

        /* Create modifiable copy of name */
        name_copy = strdup ( name );
        if ( ! name_copy )
                return NULL;
        remainder = name_copy;

        /* Parse each name component in turn */
        while ( remainder ) {
                subname = remainder;
                remainder = strchr ( subname, '.' );
                if ( remainder )
                        *(remainder++) = '\0';
                settings = get_child ( settings, subname );
                if ( ! settings )
                        break;
        }

        /* Free modifiable copy of name */
        free ( name_copy );

        return settings;
}

/**
 * Find settings block
 *
 * @v name              Name
 * @ret settings        Settings block, or NULL
 */
struct settings * find_settings ( const char *name ) {

        return parse_settings_name ( name, find_child_settings );
}

/**
 * Apply all settings
 *
 */
static void apply_settings ( void ) {
        struct settings_applicator *applicator;
        int rc;

        /* Call all settings applicators */
        for_each_table_entry ( applicator, SETTINGS_APPLICATORS ) {
                if ( ( rc = applicator->apply() ) != 0 ) {
                        DBG ( "Could not apply settings using applicator "
                              "%p: %s\n", applicator, strerror ( rc ) );
                        /* Continue to apply remaining settings */
                }
        }
}

/**
 * Reprioritise settings
 *
 * @v settings          Settings block
 *
 * Reorders the settings block amongst its siblings according to its
 * priority.
 */
static void reprioritise_settings ( struct settings *settings ) {
        struct settings *parent = settings->parent;
        long priority;
        struct settings *tmp;
        long tmp_priority;

        /* Stop when we reach the top of the tree */
        if ( ! parent )
                return;

        /* Read priority, if present */
        priority = fetch_intz_setting ( settings, &priority_setting );

        /* Remove from siblings list */
        list_del ( &settings->siblings );

        /* Reinsert after any existing blocks which have a higher priority */
        list_for_each_entry ( tmp, &parent->children, siblings ) {
                tmp_priority = fetch_intz_setting ( tmp, &priority_setting );
                if ( priority > tmp_priority )
                        break;
                if ( settings->order > tmp->order )
                        break;
        }
        list_add_tail ( &settings->siblings, &tmp->siblings );

        /* Recurse up the tree */
        reprioritise_settings ( parent );
}

/**
 * Register settings block
 *
 * @v settings          Settings block
 * @v parent            Parent settings block, or NULL
 * @v name              Settings block name
 * @ret rc              Return status code
 */
int register_settings ( struct settings *settings, struct settings *parent,
                        const char *name ) {
        struct settings *old_settings;

        /* Sanity check */
        assert ( settings != NULL );

        /* Find target parent settings block */
        parent = settings_target ( parent );

        /* Apply settings block name */
        settings->name = name;

        /* Remove any existing settings with the same name */
        if ( ( old_settings = find_child_settings ( parent, settings->name ) ))
                unregister_settings ( old_settings );

        /* Add to list of settings */
        ref_get ( settings->refcnt );
        ref_get ( parent->refcnt );
        settings->parent = parent;
        list_add_tail ( &settings->siblings, &parent->children );
        DBGC ( settings, "Settings %p (\"%s\") registered\n",
               settings, settings_name ( settings ) );

        /* Fix up settings priority */
        reprioritise_settings ( settings );

        /* Apply potentially-updated settings */
        apply_settings();

        return 0;
}

/**
 * Unregister settings block
 *
 * @v settings          Settings block
 */
void unregister_settings ( struct settings *settings ) {
        struct settings *child;

        /* Unregister child settings */
        while ( ( child = list_first_entry ( &settings->children,
                                             struct settings, siblings ) ) ) {
                unregister_settings ( child );
        }

        DBGC ( settings, "Settings %p (\"%s\") unregistered\n",
               settings, settings_name ( settings ) );

        /* Remove from list of settings */
        ref_put ( settings->parent->refcnt );
        settings->parent = NULL;
        list_del ( &settings->siblings );
        ref_put ( settings->refcnt );

        /* Apply potentially-updated settings */
        apply_settings();
}

/******************************************************************************
 *
 * Core settings routines
 *
 ******************************************************************************
 */

/**
 * Redirect to target settings block
 *
 * @v settings          Settings block, or NULL
 * @ret settings        Underlying settings block
 */
struct settings * settings_target ( struct settings *settings ) {

        /* NULL settings implies the global settings root */
        if ( ! settings )
                settings = &settings_root;

        /* Redirect to underlying settings block, if applicable */
        if ( settings->op->redirect )
                return settings->op->redirect ( settings );

        /* Otherwise, return this settings block */
        return settings;
}

/**
 * Check applicability of setting
 *
 * @v settings          Settings block
 * @v setting           Setting
 * @ret applies         Setting applies within this settings block
 */
int setting_applies ( struct settings *settings,
                      const struct setting *setting ) {

        /* Find target settings block */
        settings = settings_target ( settings );

        /* Check applicability of setting */
        return ( settings->op->applies ?
                 settings->op->applies ( settings, setting ) : 1 );
}

/**
 * Find setting applicable to settings block, if any
 *
 * @v settings          Settings block
 * @v setting           Setting
 * @ret setting         Applicable setting, if any
 */
static const struct setting *
applicable_setting ( struct settings *settings, const struct setting *setting ){
        const struct setting *applicable;

        /* If setting is already applicable, use it */
        if ( setting_applies ( settings, setting ) )
                return setting;

        /* Otherwise, look for a matching predefined setting which does apply */
        for_each_table_entry ( applicable, SETTINGS ) {
                if ( ( setting_cmp ( setting, applicable ) == 0 ) &&
                     ( setting_applies ( settings, applicable ) ) )
                        return applicable;
        }

        return NULL;
}

/**
 * Store value of setting
 *
 * @v settings          Settings block, or NULL
 * @v setting           Setting to store
 * @v data              Setting data, or NULL to clear setting
 * @v len               Length of setting data
 * @ret rc              Return status code
 */
int store_setting ( struct settings *settings, const struct setting *setting,
                    const void *data, size_t len ) {
        int rc;

        /* Find target settings block */
        settings = settings_target ( settings );

        /* Fail if setting does not apply to this settings block */
        if ( ! setting_applies ( settings, setting ) )
                return -ENOTTY;

        /* Sanity check */
        if ( ! settings->op->store )
                return -ENOTSUP;

        /* Store setting */
        if ( ( rc = settings->op->store ( settings, setting,
                                          data, len ) ) != 0 )
                return rc;

        /* Reprioritise settings if necessary */
        if ( setting_cmp ( setting, &priority_setting ) == 0 )
                reprioritise_settings ( settings );

        /* If these settings are registered, apply potentially-updated
         * settings
         */
        for ( ; settings ; settings = settings->parent ) {
                if ( settings == &settings_root ) {
                        apply_settings();
                        break;
                }
        }

        return 0;
}

/**
 * Fetch setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v origin            Origin of setting to fill in, or NULL
 * @v fetched           Fetched setting to fill in, or NULL
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 *
 * The actual length of the setting will be returned even if
 * the buffer was too small.
 */
int fetch_setting ( struct settings *settings, const struct setting *setting,
                    struct settings **origin, struct setting *fetched,
                    void *data, size_t len ) {
        const struct setting *applicable;
        struct settings *child;
        struct setting tmp;
        int ret;

        /* Avoid returning uninitialised data on error */
        memset ( data, 0, len );
        if ( origin )
                *origin = NULL;
        if ( fetched )
                memcpy ( fetched, setting, sizeof ( *fetched ) );

        /* Find target settings block */
        settings = settings_target ( settings );

        /* Sanity check */
        if ( ! settings->op->fetch )
                return -ENOTSUP;

        /* Try this block first, if an applicable setting exists */
        if ( ( applicable = applicable_setting ( settings, setting ) ) ) {

                /* Create modifiable copy of setting */
                memcpy ( &tmp, applicable, sizeof ( tmp ) );
                if ( ( ret = settings->op->fetch ( settings, &tmp,
                                                   data, len ) ) >= 0 ) {

                        /* Default to string type, if not yet specified */
                        if ( ! tmp.type )
                                tmp.type = &setting_type_string;

                        /* Record origin, if applicable */
                        if ( origin )
                                *origin = settings;

                        /* Record fetched setting, if applicable */
                        if ( fetched )
                                memcpy ( fetched, &tmp, sizeof ( *fetched ) );

                        return ret;
                }
        }

        /* Recurse into each child block in turn */
        list_for_each_entry ( child, &settings->children, siblings ) {
                if ( ( ret = fetch_setting ( child, setting, origin, fetched,
                                             data, len ) ) >= 0 )
                        return ret;
        }

        return -ENOENT;
}

/**
 * Fetch allocated copy of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v origin            Origin of setting to fill in, or NULL
 * @v fetched           Fetched setting to fill in, or NULL
 * @v data              Buffer to allocate and fill with setting data
 * @v alloc             Allocation function
 * @ret len             Length of setting, or negative error
 *
 * The caller is responsible for eventually freeing the allocated
 * buffer.
 */
static int fetch_setting_alloc ( struct settings *settings,
                                 const struct setting *setting,
                                 struct settings **origin,
                                 struct setting *fetched,
                                 void **data,
                                 void * ( * alloc ) ( size_t len ) ) {
        struct settings *tmp_origin;
        struct setting tmp_fetched;
        int len;
        int check_len;

        /* Use local buffers if necessary */
        if ( ! origin )
                origin = &tmp_origin;
        if ( ! fetched )
                fetched = &tmp_fetched;

        /* Avoid returning uninitialised data on error */
        *data = NULL;

        /* Check existence, and fetch setting length */
        len = fetch_setting ( settings, setting, origin, fetched, NULL, 0 );
        if ( len < 0 )
                return len;

        /* Allocate buffer */
        *data = alloc ( len );
        if ( ! *data )
                return -ENOMEM;

        /* Fetch setting value */
        check_len = fetch_setting ( *origin, fetched, NULL, NULL, *data, len );
        assert ( check_len == len );
        return len;
}

/**
 * Fetch copy of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v origin            Origin of setting to fill in, or NULL
 * @v fetched           Fetched setting to fill in, or NULL
 * @v data              Buffer to allocate and fill with setting data
 * @ret len             Length of setting, or negative error
 *
 * The caller is responsible for eventually freeing the allocated
 * buffer.
 */
int fetch_setting_copy ( struct settings *settings,
                         const struct setting *setting,
                         struct settings **origin, struct setting *fetched,
                         void **data ) {

        return fetch_setting_alloc ( settings, setting, origin, fetched,
                                     data, malloc );
}

/**
 * Fetch value of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v data              Buffer to fill with setting string data
 * @v len               Length of buffer
 * @ret len             Length of setting, or negative error
 */
int fetch_raw_setting ( struct settings *settings,
                        const struct setting *setting,
                        void *data, size_t len ) {

        return fetch_setting ( settings, setting, NULL, NULL, data, len );
}

/**
 * Fetch value of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v data              Buffer to allocate and fill with setting data
 * @ret len             Length of setting, or negative error
 *
 * The caller is responsible for eventually freeing the allocated
 * buffer.
 */
int fetch_raw_setting_copy ( struct settings *settings,
                             const struct setting *setting,
                             void **data ) {

        return fetch_setting_copy ( settings, setting, NULL, NULL, data );
}

/**
 * Fetch value of string setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v data              Buffer to fill with setting string data
 * @v len               Length of buffer
 * @ret len             Length of string setting, or negative error
 *
 * The resulting string is guaranteed to be correctly NUL-terminated.
 * The returned length will be the length of the underlying setting
 * data.
 */
int fetch_string_setting ( struct settings *settings,
                           const struct setting *setting,
                           char *data, size_t len ) {

        memset ( data, 0, len );
        return fetch_raw_setting ( settings, setting, data,
                                   ( ( len > 0 ) ? ( len - 1 ) : 0 ) );
}

/**
 * Allocate memory for copy of string setting
 *
 * @v len               Length of setting
 * @ret ptr             Allocated memory
 */
static void * fetch_string_setting_copy_alloc ( size_t len ) {
        return zalloc ( len + 1 /* NUL */ );
}

/**
 * Fetch value of string setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v data              Buffer to allocate and fill with setting string data
 * @ret len             Length of string setting, or negative error
 *
 * The resulting string is guaranteed to be correctly NUL-terminated.
 * The returned length will be the length of the underlying setting
 * data.  The caller is responsible for eventually freeing the
 * allocated buffer.
 */
int fetch_string_setting_copy ( struct settings *settings,
                                const struct setting *setting, char **data ) {

        return fetch_setting_alloc ( settings, setting, NULL, NULL,
                                     ( ( void ** ) data ),
                                     fetch_string_setting_copy_alloc );
}

/**
 * Fetch value of IPv4 address setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v inp               IPv4 addresses to fill in
 * @v count             Maximum number of IPv4 addresses
 * @ret len             Length of setting, or negative error
 */
int fetch_ipv4_array_setting ( struct settings *settings,
                               const struct setting *setting,
                               struct in_addr *inp, unsigned int count ) {
        int len;

        len = fetch_raw_setting ( settings, setting, inp,
                                  ( sizeof ( *inp ) * count ) );
        if ( len < 0 )
                return len;
        if ( ( len % sizeof ( *inp ) ) != 0 )
                return -ERANGE;
        return len;
}

/**
 * Fetch value of IPv4 address setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v inp               IPv4 address to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_ipv4_setting ( struct settings *settings,
                         const struct setting *setting,
                         struct in_addr *inp ) {

        return fetch_ipv4_array_setting ( settings, setting, inp, 1 );
}

/**
 * Fetch value of IPv6 address setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v inp               IPv6 addresses to fill in
 * @v count             Maximum number of IPv6 addresses
 * @ret len             Length of setting, or negative error
 */
int fetch_ipv6_array_setting ( struct settings *settings,
                               const struct setting *setting,
                               struct in6_addr *inp, unsigned int count ) {
        int len;

        len = fetch_raw_setting ( settings, setting, inp,
                                  ( sizeof ( *inp ) * count ) );
        if ( len < 0 )
                return len;
        if ( ( len % sizeof ( *inp ) ) != 0 )
                return -ERANGE;
        return len;
}

/**
 * Fetch value of IPv6 address setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v inp               IPv6 address to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_ipv6_setting ( struct settings *settings,
                         const struct setting *setting,
                         struct in6_addr *inp ) {

        return fetch_ipv6_array_setting ( settings, setting, inp, 1 );
}

/**
 * Extract numeric value of setting
 *
 * @v is_signed         Treat value as a signed integer
 * @v raw               Raw setting data
 * @v len               Length of raw setting data
 * @ret value           Numeric value
 * @ret len             Length of setting, or negative error
 */
static int numeric_setting_value ( int is_signed, const void *raw, size_t len,
                                   unsigned long *value ) {
        const uint8_t *unsigned_bytes = raw;
        const int8_t *signed_bytes = raw;
        int is_negative;
        unsigned int i;
        uint8_t pad;
        uint8_t byte;

        /* Convert to host-ordered longs */
        is_negative = ( len && ( signed_bytes[0] < 0 ) );
        *value = ( ( is_signed && is_negative ) ? -1L : 0 );
        pad = *value;
        for ( i = 0 ; i < len ; i++ ) {
                byte = unsigned_bytes[i];
                *value = ( ( *value << 8 ) | byte );
                if ( ( ( i + sizeof ( *value ) ) < len ) && ( byte != pad ) )
                        return -ERANGE;
        }

        return len;
}

/**
 * Fetch value of numeric setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v value             Integer value to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_numeric_setting ( struct settings *settings,
                            const struct setting *setting,
                            unsigned long *value, int is_signed ) {
        unsigned long tmp;
        int len;

        /* Avoid returning uninitialised data on error */
        *value = 0;

        /* Fetch raw (network-ordered, variable-length) setting */
        len = fetch_raw_setting ( settings, setting, &tmp, sizeof ( tmp ) );
        if ( len < 0 )
                return len;

        /* Extract numeric value */
        return numeric_setting_value ( is_signed, &tmp, len, value );
}

/**
 * Fetch value of signed integer setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v value             Integer value to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_int_setting ( struct settings *settings,
                        const struct setting *setting,
                        long *value ) {

        return fetch_numeric_setting ( settings, setting,
                                       ( ( unsigned long * ) value ), 1 );
}

/**
 * Fetch value of unsigned integer setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v value             Integer value to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_uint_setting ( struct settings *settings,
                         const struct setting *setting,
                         unsigned long *value ) {

        return fetch_numeric_setting ( settings, setting, value, 0 );
}

/**
 * Fetch value of signed integer setting, or zero
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @ret value           Setting value, or zero
 */
long fetch_intz_setting ( struct settings *settings,
                          const struct setting *setting ) {
        unsigned long value;

        fetch_numeric_setting ( settings, setting, &value, 1 );
        return value;
}

/**
 * Fetch value of unsigned integer setting, or zero
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @ret value           Setting value, or zero
 */
unsigned long fetch_uintz_setting ( struct settings *settings,
                                    const struct setting *setting ) {
        unsigned long value;

        fetch_numeric_setting ( settings, setting, &value, 0 );
        return value;
}

/**
 * Fetch value of UUID setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v uuid              UUID to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_uuid_setting ( struct settings *settings,
                         const struct setting *setting,
                         union uuid *uuid ) {
        int len;

        len = fetch_raw_setting ( settings, setting, uuid, sizeof ( *uuid ) );
        if ( len < 0 )
                return len;
        if ( len != sizeof ( *uuid ) )
                return -ERANGE;
        return len;
}

/**
 * Clear settings block
 *
 * @v settings          Settings block
 */
void clear_settings ( struct settings *settings ) {

        /* Find target settings block */
        settings = settings_target ( settings );

        /* Clear settings, if applicable */
        if ( settings->op->clear )
                settings->op->clear ( settings );
}

/**
 * Compare two settings
 *
 * @v a                 Setting to compare
 * @v b                 Setting to compare
 * @ret 0               Settings are the same
 * @ret non-zero        Settings are not the same
 */
int setting_cmp ( const struct setting *a, const struct setting *b ) {

        /* If the settings have tags, compare them */
        if ( a->tag && ( a->tag == b->tag ) && ( a->scope == b->scope ) )
                return 0;

        /* Otherwise, if the settings have names, compare them */
        if ( a->name && b->name && a->name[0] )
                return strcmp ( a->name, b->name );

        /* Otherwise, return a non-match */
        return ( ! 0 );
}

/******************************************************************************
 *
 * Formatted setting routines
 *
 ******************************************************************************
 */

/**
 * Format setting value as a string
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
int setting_format ( const struct setting_type *type, const void *raw,
                     size_t raw_len, char *buf, size_t len ) {

        /* Sanity check */
        if ( ! type->format )
                return -ENOTSUP;

        return type->format ( type, raw, raw_len, buf, len );
}

/**
 * Parse formatted string to setting value
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
int setting_parse ( const struct setting_type *type, const char *value,
                    void *buf, size_t len ) {

        /* Sanity check */
        if ( ! type->parse )
                return -ENOTSUP;

        return type->parse ( type, value, buf, len );
}

/**
 * Convert setting value to number
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @ret value           Numeric value
 * @ret rc              Return status code
 */
int setting_numerate ( const struct setting_type *type, const void *raw,
                       size_t raw_len, unsigned long *value ) {

        /* Sanity check */
        if ( ! type->numerate )
                return -ENOTSUP;

        return type->numerate ( type, raw, raw_len, value );
}

/**
 * Convert number to setting value
 *
 * @v type              Setting type
 * @v value             Numeric value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
int setting_denumerate ( const struct setting_type *type, unsigned long value,
                         void *buf, size_t len ) {

        /* Sanity check */
        if ( ! type->denumerate )
                return -ENOTSUP;

        return type->denumerate ( type, value, buf, len );
}

/**
 * Fetch formatted value of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v origin            Origin of setting to fill in, or NULL
 * @v fetched           Fetched setting to fill in, or NULL
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
int fetchf_setting ( struct settings *settings, const struct setting *setting,
                     struct settings **origin, struct setting *fetched,
                     char *buf, size_t len ) {
        struct setting tmp_fetched;
        void *raw;
        int raw_len;
        int ret;

        /* Use local buffers if necessary */
        if ( ! fetched )
                fetched = &tmp_fetched;

        /* Fetch raw value */
        raw_len = fetch_setting_copy ( settings, setting, origin, fetched,
                                       &raw );
        if ( raw_len < 0 ) {
                ret = raw_len;
                goto err_fetch_copy;
        }

        /* Sanity check */
        assert ( fetched->type != NULL );

        /* Format setting */
        if ( ( ret = setting_format ( fetched->type, raw, raw_len, buf,
                                      len ) ) < 0 )
                goto err_format;

 err_format:
        free ( raw );
 err_fetch_copy:
        return ret;
}

/**
 * Fetch copy of formatted value of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v origin            Origin of setting to fill in, or NULL
 * @v fetched           Fetched setting to fill in, or NULL
 * @v value             Buffer to allocate and fill with formatted value
 * @ret len             Length of formatted value, or negative error
 *
 * The caller is responsible for eventually freeing the allocated
 * buffer.
 */
int fetchf_setting_copy ( struct settings *settings,
                          const struct setting *setting,
                          struct settings **origin, struct setting *fetched,
                          char **value ) {
        struct settings *tmp_origin;
        struct setting tmp_fetched;
        int len;
        int check_len;

        /* Use local buffers if necessary */
        if ( ! origin )
                origin = &tmp_origin;
        if ( ! fetched )
                fetched = &tmp_fetched;

        /* Avoid returning uninitialised data on error */
        *value = NULL;

        /* Check existence, and fetch formatted value length */
        len = fetchf_setting ( settings, setting, origin, fetched, NULL, 0 );
        if ( len < 0 )
                return len;

        /* Allocate buffer */
        *value = zalloc ( len + 1 /* NUL */ );
        if ( ! *value )
                return -ENOMEM;

        /* Fetch formatted value */
        check_len = fetchf_setting ( *origin, fetched, NULL, NULL, *value,
                                     ( len + 1 /* NUL */ ) );
        assert ( check_len == len );
        return len;
}

/**
 * Store formatted value of setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data, or NULL
 * @ret rc              Return status code
 */
int storef_setting ( struct settings *settings, const struct setting *setting,
                     const char *value ) {
        void *raw;
        int raw_len;
        int check_len;
        int rc;

        /* NULL value or empty string implies deletion */
        if ( ( ! value ) || ( ! value[0] ) )
                return delete_setting ( settings, setting );

        /* Sanity check */
        assert ( setting->type != NULL );

        /* Get raw value length */
        raw_len = setting_parse ( setting->type, value, NULL, 0 );
        if ( raw_len < 0 ) {
                rc = raw_len;
                goto err_raw_len;
        }

        /* Allocate buffer for raw value */
        raw = malloc ( raw_len );
        if ( ! raw ) {
                rc = -ENOMEM;
                goto err_alloc_raw;
        }

        /* Parse formatted value */
        check_len = setting_parse ( setting->type, value, raw, raw_len );
        assert ( check_len == raw_len );

        /* Store raw value */
        if ( ( rc = store_setting ( settings, setting, raw, raw_len ) ) != 0 )
                goto err_store;

 err_store:
        free ( raw );
 err_alloc_raw:
 err_raw_len:
        return rc;
}

/**
 * Fetch numeric value of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v origin            Origin of setting to fill in, or NULL
 * @v fetched           Fetched setting to fill in, or NULL
 * @v value             Numeric value to fill in
 * @ret rc              Return status code
 */
int fetchn_setting ( struct settings *settings, const struct setting *setting,
                     struct settings **origin, struct setting *fetched,
                     unsigned long *value ) {
        struct setting tmp_fetched;
        void *raw;
        int raw_len;
        int rc;

        /* Use local buffers if necessary */
        if ( ! fetched )
                fetched = &tmp_fetched;

        /* Fetch raw value */
        raw_len = fetch_setting_copy ( settings, setting, origin, fetched,
                                       &raw );
        if ( raw_len < 0 ) {
                rc = raw_len;
                goto err_fetch_copy;
        }

        /* Sanity check */
        assert ( fetched->type != NULL );

        /* Numerate setting */
        if ( ( rc = setting_numerate ( fetched->type, raw, raw_len,
                                       value ) ) < 0 )
                goto err_numerate;

 err_numerate:
        free ( raw );
 err_fetch_copy:
        return rc;
}

/**
 * Store numeric value of setting
 *
 * @v settings          Settings block
 * @v setting           Setting
 * @v value             Numeric value
 * @ret rc              Return status code
 */
int storen_setting ( struct settings *settings, const struct setting *setting,
                     unsigned long value ) {
        void *raw;
        int raw_len;
        int check_len;
        int rc;

        /* Sanity check */
        assert ( setting->type != NULL );

        /* Get raw value length */
        raw_len = setting_denumerate ( setting->type, value, NULL, 0 );
        if ( raw_len < 0 ) {
                rc = raw_len;
                goto err_raw_len;
        }

        /* Allocate buffer for raw value */
        raw = malloc ( raw_len );
        if ( ! raw ) {
                rc = -ENOMEM;
                goto err_alloc_raw;
        }

        /* Denumerate value */
        check_len = setting_denumerate ( setting->type, value, raw, raw_len );
        assert ( check_len == raw_len );

        /* Store raw value */
        if ( ( rc = store_setting ( settings, setting, raw, raw_len ) ) != 0 )
                goto err_store;

 err_store:
        free ( raw );
 err_alloc_raw:
 err_raw_len:
        return rc;
}

/******************************************************************************
 *
 * Named settings
 *
 ******************************************************************************
 */

/**
 * Find predefined setting
 *
 * @v name              Name
 * @ret setting         Setting, or NULL
 */
struct setting * find_setting ( const char *name ) {
        struct setting *setting;

        for_each_table_entry ( setting, SETTINGS ) {
                if ( strcmp ( name, setting->name ) == 0 )
                        return setting;
        }
        return NULL;
}

/**
 * Parse setting name as tag number
 *
 * @v name              Name
 * @ret tag             Tag number, or 0 if not a valid number
 */
static uint64_t parse_setting_tag ( const char *name ) {
        char *tmp = ( ( char * ) name );
        uint64_t tag = 0;

        while ( 1 ) {
                tag = ( ( tag << 8 ) | strtoul ( tmp, &tmp, 0 ) );
                if ( *tmp == 0 )
                        return tag;
                if ( *tmp != '.' )
                        return 0;
                tmp++;
        }
}

/**
 * Find setting type
 *
 * @v name              Name
 * @ret type            Setting type, or NULL
 */
static const struct setting_type * find_setting_type ( const char *name ) {
        const struct setting_type *type;

        for_each_table_entry ( type, SETTING_TYPES ) {
                if ( strcmp ( name, type->name ) == 0 )
                        return type;
        }
        return NULL;
}

/**
 * Parse setting name
 *
 * @v name              Name of setting
 * @v get_child         Function to find or create child settings block
 * @v settings          Settings block to fill in
 * @v setting           Setting to fill in
 * @ret rc              Return status code
 *
 * Interprets a name of the form
 * "[settings_name/]tag_name[:type_name]" and fills in the appropriate
 * fields.
 *
 * Note that on success, this function will have modified the original
 * setting @c name.
 */
int parse_setting_name ( char *name, get_child_settings_t get_child,
                         struct settings **settings, struct setting *setting ) {
        char *settings_name;
        char *setting_name;
        char *type_name;
        struct setting *predefined;
        int rc;

        /* Set defaults */
        *settings = &settings_root;
        memset ( setting, 0, sizeof ( *setting ) );
        setting->name = "";

        /* Split name into "[settings_name/]setting_name[:type_name]" */
        if ( ( setting_name = strchr ( name, '/' ) ) != NULL ) {
                *(setting_name++) = 0;
                settings_name = name;
        } else {
                setting_name = name;
                settings_name = NULL;
        }
        if ( ( type_name = strchr ( setting_name, ':' ) ) != NULL )
                *(type_name++) = 0;

        /* Identify settings block, if specified */
        if ( settings_name ) {
                *settings = parse_settings_name ( settings_name, get_child );
                if ( *settings == NULL ) {
                        DBG ( "Unrecognised settings block \"%s\" in \"%s\"\n",
                              settings_name, name );
                        rc = -ENODEV;
                        goto err;
                }
        }

        /* Identify setting */
        setting->tag = parse_setting_tag ( setting_name );
        setting->scope = (*settings)->default_scope;
        setting->name = setting_name;
        for_each_table_entry ( predefined, SETTINGS ) {
                /* Matches a predefined setting; use that setting */
                if ( setting_cmp ( predefined, setting ) == 0 ) {
                        memcpy ( setting, predefined, sizeof ( *setting ) );
                        break;
                }
        }

        /* Identify setting type, if specified */
        if ( type_name ) {
                setting->type = find_setting_type ( type_name );
                if ( setting->type == NULL ) {
                        DBG ( "Invalid setting type \"%s\" in \"%s\"\n",
                              type_name, name );
                        rc = -ENOTSUP;
                        goto err;
                }
        }

        return 0;

 err:
        /* Restore original name */
        if ( settings_name )
                *( setting_name - 1 ) = '/';
        if ( type_name )
                *( type_name - 1 ) = ':';
        return rc;
}

/**
 * Return full setting name
 *
 * @v settings          Settings block, or NULL
 * @v setting           Setting
 * @v buf               Buffer
 * @v len               Length of buffer
 * @ret len             Length of setting name, or negative error
 */
int setting_name ( struct settings *settings, const struct setting *setting,
                   char *buf, size_t len ) {
        const char *name;

        settings = settings_target ( settings );
        name = settings_name ( settings );
        return snprintf ( buf, len, "%s%s%s:%s", name, ( name[0] ? "/" : "" ),
                          setting->name, setting->type->name );
}

/******************************************************************************
 *
 * Setting types
 *
 ******************************************************************************
 */

/**
 * Parse string setting value
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
static int parse_string_setting ( const struct setting_type *type __unused,
                                  const char *value, void *buf, size_t len ) {
        size_t raw_len = strlen ( value ); /* Exclude terminating NUL */

        /* Copy string to buffer */
        if ( len > raw_len )
                len = raw_len;
        memcpy ( buf, value, len );

        return raw_len;
}

/**
 * Format string setting value
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_string_setting ( const struct setting_type *type __unused,
                                   const void *raw, size_t raw_len, char *buf,
                                   size_t len ) {

        /* Copy string to buffer, and terminate */
        memset ( buf, 0, len );
        if ( len > raw_len )
                len = raw_len;
        memcpy ( buf, raw, len );

        return raw_len;
}

/** A string setting type */
const struct setting_type setting_type_string __setting_type = {
        .name = "string",
        .parse = parse_string_setting,
        .format = format_string_setting,
};

/**
 * Parse URI-encoded string setting value
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
static int parse_uristring_setting ( const struct setting_type *type __unused,
                                     const char *value, void *buf, size_t len ){

        return uri_decode ( value, buf, len );
}

/**
 * Format URI-encoded string setting value
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_uristring_setting ( const struct setting_type *type __unused,
                                      const void *raw, size_t raw_len,
                                      char *buf, size_t len ) {

        return uri_encode ( 0, raw, raw_len, buf, len );
}

/** A URI-encoded string setting type */
const struct setting_type setting_type_uristring __setting_type = {
        .name = "uristring",
        .parse = parse_uristring_setting,
        .format = format_uristring_setting,
};

/**
 * Parse IPv4 address setting value (when IPv4 support is not present)
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
__weak int parse_ipv4_setting ( const struct setting_type *type __unused,
                                const char *value __unused, void *buf __unused,
                                size_t len __unused ) {
        return -ENOTSUP;
}

/**
 * Format IPv4 address setting value (when IPv4 support is not present)
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
__weak int format_ipv4_setting ( const struct setting_type *type __unused,
                                 const void *raw __unused,
                                 size_t raw_len __unused, char *buf __unused,
                                 size_t len __unused ) {
        return -ENOTSUP;
}

/** An IPv4 address setting type */
const struct setting_type setting_type_ipv4 __setting_type = {
        .name = "ipv4",
        .parse = parse_ipv4_setting,
        .format = format_ipv4_setting,
};

/**
 * Parse IPv6 address setting value (when IPv6 support is not present)
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
__weak int parse_ipv6_setting ( const struct setting_type *type __unused,
                                const char *value __unused, void *buf __unused,
                                size_t len __unused ) {
        return -ENOTSUP;
}

/**
 * Format IPv6 address setting value (when IPv6 support is not present)
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
__weak int format_ipv6_setting ( const struct setting_type *type __unused,
                                 const void *raw __unused,
                                 size_t raw_len __unused, char *buf __unused,
                                 size_t len __unused ) {
        return -ENOTSUP;
}

/** An IPv6 address setting type */
const struct setting_type setting_type_ipv6 __setting_type = {
        .name = "ipv6",
        .parse = parse_ipv6_setting,
        .format = format_ipv6_setting,
};

/** IPv6 settings scope */
const struct settings_scope dhcpv6_scope;

/**
 * Integer setting type indices
 *
 * These indexes are defined such that (1<<index) gives the width of
 * the integer, in bytes.
 */
enum setting_type_int_index {
        SETTING_TYPE_INT8 = 0,
        SETTING_TYPE_INT16 = 1,
        SETTING_TYPE_INT32 = 2,
};

/**
 * Integer setting type names
 *
 * These names exist as a static array in order to allow the type's
 * integer size and signedness to be determined from the type's name.
 * Note that there are no separate entries for the signed integer
 * types: the name pointers simply point to the second character of
 * the relevant string.
 */
static const char setting_type_int_name[][8] = {
        [SETTING_TYPE_INT8] = "uint8",
        [SETTING_TYPE_INT16] = "uint16",
        [SETTING_TYPE_INT32] = "uint32",
};

/**
 * Get unsigned integer setting type name
 *
 * @v index             Integer setting type index
 * @ret name            Setting type name
 */
#define SETTING_TYPE_UINT_NAME( index ) setting_type_int_name[index]

/**
 * Get signed integer setting type name
 *
 * @v index             Integer setting type index
 * @ret name            Setting type name
 */
#define SETTING_TYPE_INT_NAME( index ) ( setting_type_int_name[index] + 1 )

/**
 * Get integer setting type index
 *
 * @v type              Setting type
 * @ret index           Integer setting type index
 */
static unsigned int setting_type_int_index ( const struct setting_type *type ) {

        return ( ( type->name - setting_type_int_name[0] ) /
                 sizeof ( setting_type_int_name[0] ) );
}

/**
 * Get integer setting type width
 *
 * @v type              Setting type
 * @ret index           Integer setting type width
 */
static unsigned int setting_type_int_width ( const struct setting_type *type ) {

        return ( 1 << setting_type_int_index ( type ) );
}

/**
 * Get integer setting type signedness
 *
 * @v type              Setting type
 * @ret is_signed       Integer setting type is signed
 */
static int setting_type_int_is_signed ( const struct setting_type *type ) {
        return ( ( type->name - setting_type_int_name[0] ) & 1 );
}

/**
 * Convert number to setting value
 *
 * @v type              Setting type
 * @v value             Numeric value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
static int denumerate_int_setting ( const struct setting_type *type,
                                    unsigned long value, void *buf,
                                    size_t len ) {
        unsigned int size = setting_type_int_width ( type );
        union {
                uint32_t num;
                uint8_t bytes[4];
        } u;

        u.num = htonl ( value );
        if ( len > size )
                len = size;
        memcpy ( buf, &u.bytes[ sizeof ( u ) - size ], len );

        return size;
}

/**
 * Convert setting value to number
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v value             Numeric value to fill in
 * @ret rc              Return status code
 */
static int numerate_int_setting ( const struct setting_type *type,
                                  const void *raw, size_t raw_len,
                                  unsigned long *value ) {
        int is_signed = setting_type_int_is_signed ( type );
        int check_len;

        /* Extract numeric value */
        check_len = numeric_setting_value ( is_signed, raw, raw_len, value );
        if ( check_len < 0 )
                return check_len;
        assert ( check_len == ( int ) raw_len );

        return 0;
}

/**
 * Parse integer setting value
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
static int parse_int_setting ( const struct setting_type *type,
                               const char *value, void *buf, size_t len ) {
        char *endp;
        unsigned long num_value;

        /* Parse value */
        num_value = strtoul ( value, &endp, 0 );
        if ( *endp )
                return -EINVAL;

        return type->denumerate ( type, num_value, buf, len );
}

/**
 * Format signed integer setting value
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_int_setting ( const struct setting_type *type,
                                const void *raw, size_t raw_len,
                                char *buf, size_t len ) {
        unsigned long value;
        int ret;

        /* Extract numeric value */
        if ( ( ret = type->numerate ( type, raw, raw_len, &value ) ) < 0 )
                return ret;

        /* Format value */
        return snprintf ( buf, len, "%ld", value );
}

/**
 * Format unsigned integer setting value
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_uint_setting ( const struct setting_type *type,
                                 const void *raw, size_t raw_len,
                                 char *buf, size_t len ) {
        unsigned long value;
        int ret;

        /* Extract numeric value */
        if ( ( ret = type->numerate ( type, raw, raw_len, &value ) ) < 0 )
                return ret;

        /* Format value */
        return snprintf ( buf, len, "%#lx", value );
}

/**
 * Define a signed integer setting type
 *
 * @v index             Integer setting type index
 * @ret type            Setting type
 */
#define SETTING_TYPE_INT( index ) {                             \
        .name = SETTING_TYPE_INT_NAME ( index ),                \
        .parse = parse_int_setting,                             \
        .format = format_int_setting,                           \
        .denumerate = denumerate_int_setting,                   \
        .numerate = numerate_int_setting,                       \
}

/**
 * Define an unsigned integer setting type
 *
 * @v index             Integer setting type index
 * @ret type            Setting type
 */
#define SETTING_TYPE_UINT( index ) {                            \
        .name = SETTING_TYPE_UINT_NAME ( index ),               \
        .parse = parse_int_setting,                             \
        .format = format_uint_setting,                          \
        .denumerate = denumerate_int_setting,                   \
        .numerate = numerate_int_setting,                       \
}

/** A signed 8-bit integer setting type */
const struct setting_type setting_type_int8 __setting_type =
        SETTING_TYPE_INT ( SETTING_TYPE_INT8 );

/** A signed 16-bit integer setting type */
const struct setting_type setting_type_int16 __setting_type =
        SETTING_TYPE_INT ( SETTING_TYPE_INT16 );

/** A signed 32-bit integer setting type */
const struct setting_type setting_type_int32 __setting_type =
        SETTING_TYPE_INT ( SETTING_TYPE_INT32 );

/** An unsigned 8-bit integer setting type */
const struct setting_type setting_type_uint8 __setting_type =
        SETTING_TYPE_UINT ( SETTING_TYPE_INT8 );

/** An unsigned 16-bit integer setting type */
const struct setting_type setting_type_uint16 __setting_type =
        SETTING_TYPE_UINT ( SETTING_TYPE_INT16 );

/** An unsigned 32-bit integer setting type */
const struct setting_type setting_type_uint32 __setting_type =
        SETTING_TYPE_UINT ( SETTING_TYPE_INT32 );

/**
 * Parse hex string setting value (using colon delimiter)
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @v size              Integer size, in bytes
 * @ret len             Length of raw value, or negative error
 */
static int parse_hex_setting ( const struct setting_type *type __unused,
                               const char *value, void *buf, size_t len ) {
        return hex_decode ( ':', value, buf, len );
}

/**
 * Format hex string setting value (using colon delimiter)
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_hex_colon_setting ( const struct setting_type *type __unused,
                                      const void *raw, size_t raw_len,
                                      char *buf, size_t len ) {
        return hex_encode ( ':', raw, raw_len, buf, len );
}

/**
 * Parse hex string setting value (using hyphen delimiter)
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @v size              Integer size, in bytes
 * @ret len             Length of raw value, or negative error
 */
static int parse_hex_hyphen_setting ( const struct setting_type *type __unused,
                                      const char *value, void *buf,
                                      size_t len ) {
        return hex_decode ( '-', value, buf, len );
}

/**
 * Format hex string setting value (using hyphen delimiter)
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_hex_hyphen_setting ( const struct setting_type *type __unused,
                                       const void *raw, size_t raw_len,
                                       char *buf, size_t len ) {
        return hex_encode ( '-', raw, raw_len, buf, len );
}

/**
 * Parse hex string setting value (using no delimiter)
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @v size              Integer size, in bytes
 * @ret len             Length of raw value, or negative error
 */
static int parse_hex_raw_setting ( const struct setting_type *type __unused,
                                   const char *value, void *buf, size_t len ) {
        return hex_decode ( 0, value, buf, len );
}

/**
 * Format hex string setting value (using no delimiter)
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_hex_raw_setting ( const struct setting_type *type __unused,
                                    const void *raw, size_t raw_len,
                                    char *buf, size_t len ) {
        return hex_encode ( 0, raw, raw_len, buf, len );
}

/** A hex-string setting (colon-delimited) */
const struct setting_type setting_type_hex __setting_type = {
        .name = "hex",
        .parse = parse_hex_setting,
        .format = format_hex_colon_setting,
};

/** A hex-string setting (hyphen-delimited) */
const struct setting_type setting_type_hexhyp __setting_type = {
        .name = "hexhyp",
        .parse = parse_hex_hyphen_setting,
        .format = format_hex_hyphen_setting,
};

/** A hex-string setting (non-delimited) */
const struct setting_type setting_type_hexraw __setting_type = {
        .name = "hexraw",
        .parse = parse_hex_raw_setting,
        .format = format_hex_raw_setting,
};

/**
 * Parse Base64-encoded setting value
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @v size              Integer size, in bytes
 * @ret len             Length of raw value, or negative error
 */
static int parse_base64_setting ( const struct setting_type *type __unused,
                                  const char *value, void *buf, size_t len ) {

        return base64_decode ( value, buf, len );
}

/**
 * Format Base64-encoded setting value
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_base64_setting ( const struct setting_type *type __unused,
                                   const void *raw, size_t raw_len,
                                   char *buf, size_t len ) {

        return base64_encode ( raw, raw_len, buf, len );
}

/** A Base64-encoded setting */
const struct setting_type setting_type_base64 __setting_type = {
        .name = "base64",
        .parse = parse_base64_setting,
        .format = format_base64_setting,
};

/**
 * Parse UUID/GUID setting value
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @v size              Integer size, in bytes
 * @ret len             Length of raw value, or negative error
 */
static int parse_uuid_setting ( const struct setting_type *type,
                                const char *value, void *buf, size_t len ) {
        union uuid uuid;
        int rc;

        /* Parse UUID */
        if ( ( rc = uuid_aton ( value, &uuid ) ) != 0 )
                return rc;

        /* Mangle GUID byte ordering */
        if ( type == &setting_type_guid )
                uuid_mangle ( &uuid );

        /* Copy value */
        if ( len > sizeof ( uuid ) )
                len = sizeof ( uuid );
        memcpy ( buf, uuid.raw, len );

        return ( sizeof ( uuid ) );
}

/**
 * Format UUID/GUID setting value
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_uuid_setting ( const struct setting_type *type,
                                 const void *raw, size_t raw_len, char *buf,
                                 size_t len ) {
        union uuid uuid;

        /* Range check */
        if ( raw_len != sizeof ( uuid ) )
                return -ERANGE;

        /* Copy value */
        memcpy ( &uuid, raw, sizeof ( uuid ) );

        /* Mangle GUID byte ordering */
        if ( type == &setting_type_guid )
                uuid_mangle ( &uuid );

        /* Format value */
        return snprintf ( buf, len, "%s", uuid_ntoa ( &uuid ) );
}

/** UUID setting type */
const struct setting_type setting_type_uuid __setting_type = {
        .name = "uuid",
        .parse = parse_uuid_setting,
        .format = format_uuid_setting,
};

/** GUID setting type */
const struct setting_type setting_type_guid __setting_type = {
        .name = "guid",
        .parse = parse_uuid_setting,
        .format = format_uuid_setting,
};

/**
 * Format PCI bus:dev.fn setting value
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int format_busdevfn_setting ( const struct setting_type *type __unused,
                                     const void *raw, size_t raw_len, char *buf,
                                     size_t len ) {
        unsigned long busdevfn;
        unsigned int seg;
        unsigned int bus;
        unsigned int slot;
        unsigned int func;
        int check_len;

        /* Extract numeric value */
        check_len = numeric_setting_value ( 0, raw, raw_len, &busdevfn );
        if ( check_len < 0 )
                return check_len;
        assert ( check_len == ( int ) raw_len );

        /* Extract PCI address components */
        seg = PCI_SEG ( busdevfn );
        bus = PCI_BUS ( busdevfn );
        slot = PCI_SLOT ( busdevfn );
        func = PCI_FUNC ( busdevfn );

        /* Format value */
        return snprintf ( buf, len, "%04x:%02x:%02x.%x", seg, bus, slot, func );
}

/** PCI bus:dev.fn setting type */
const struct setting_type setting_type_busdevfn __setting_type = {
        .name = "busdevfn",
        .format = format_busdevfn_setting,
};

/******************************************************************************
 *
 * Setting expansion
 *
 ******************************************************************************
 */

/**
 * Expand variables within string
 *
 * @v string            String
 * @ret expstr          Expanded string
 *
 * The expanded string is allocated with malloc() and the caller must
 * eventually free() it.
 */
char * expand_settings ( const char *string ) {
        struct settings *settings;
        struct setting setting;
        char *expstr;
        char *start;
        char *end;
        char *head;
        char *name;
        char *tail;
        char *value;
        char *tmp;
        int new_len;
        int rc;

        /* Obtain temporary modifiable copy of string */
        expstr = strdup ( string );
        if ( ! expstr )
                return NULL;

        /* Expand while expansions remain */
        while ( 1 ) {

                head = expstr;

                /* Locate setting to be expanded */
                start = NULL;
                end = NULL;
                for ( tmp = expstr ; *tmp ; tmp++ ) {
                        if ( ( tmp[0] == '$' ) && ( tmp[1] == '{' ) )
                                start = tmp;
                        if ( start && ( tmp[0] == '}' ) ) {
                                end = tmp;
                                break;
                        }
                }
                if ( ! end )
                        break;
                *start = '\0';
                name = ( start + 2 );
                *end = '\0';
                tail = ( end + 1 );

                /* Expand setting */
                if ( ( rc = parse_setting_name ( name, find_child_settings,
                                                 &settings,
                                                 &setting ) ) != 0 ) {
                        /* Treat invalid setting names as empty */
                        value = NULL;
                } else {
                        /* Fetch and format setting value.  Ignore
                         * errors; treat non-existent settings as empty.
                         */
                        fetchf_setting_copy ( settings, &setting, NULL, NULL,
                                              &value );
                }

                /* Construct expanded string and discard old string */
                tmp = expstr;
                new_len = asprintf ( &expstr, "%s%s%s",
                                     head, ( value ? value : "" ), tail );
                free ( value );
                free ( tmp );
                if ( new_len < 0 )
                        return NULL;
        }

        return expstr;
}

/******************************************************************************
 *
 * Settings
 *
 ******************************************************************************
 */

/** Hostname setting */
const struct setting hostname_setting __setting ( SETTING_HOST, hostname ) = {
        .name = "hostname",
        .description = "Host name",
        .tag = DHCP_HOST_NAME,
        .type = &setting_type_string,
};

/** Domain name setting */
const struct setting domain_setting __setting ( SETTING_IP_EXTRA, domain ) = {
        .name = "domain",
        .description = "DNS domain",
        .tag = DHCP_DOMAIN_NAME,
        .type = &setting_type_string,
};

/** TFTP server setting */
const struct setting next_server_setting __setting ( SETTING_BOOT,next-server)={
        .name = "next-server",
        .description = "TFTP server",
        .tag = DHCP_EB_SIADDR,
        .type = &setting_type_ipv4,
};

/** Filename setting */
const struct setting filename_setting __setting ( SETTING_BOOT, filename ) = {
        .name = "filename",
        .description = "Boot filename",
        .tag = DHCP_BOOTFILE_NAME,
        .type = &setting_type_string,
};

/** Root path setting */
const struct setting root_path_setting __setting ( SETTING_SANBOOT, root-path)={
        .name = "root-path",
        .description = "SAN root path",
        .tag = DHCP_ROOT_PATH,
        .type = &setting_type_string,
};

/** SAN filename setting */
const struct setting san_filename_setting __setting ( SETTING_SANBOOT,
                                                      san-filename ) = {
        .name = "san-filename",
        .description = "SAN filename",
        .tag = DHCP_EB_SAN_FILENAME,
        .type = &setting_type_string,
};

/** Username setting */
const struct setting username_setting __setting ( SETTING_AUTH, username ) = {
        .name = "username",
        .description = "User name",
        .tag = DHCP_EB_USERNAME,
        .type = &setting_type_string,
};

/** Password setting */
const struct setting password_setting __setting ( SETTING_AUTH, password ) = {
        .name = "password",
        .description = "Password",
        .tag = DHCP_EB_PASSWORD,
        .type = &setting_type_string,
};

/** Priority setting */
const struct setting priority_setting __setting ( SETTING_MISC, priority ) = {
        .name = "priority",
        .description = "Settings priority",
        .tag = DHCP_EB_PRIORITY,
        .type = &setting_type_int8,
};

/** DHCP user class setting */
const struct setting user_class_setting __setting ( SETTING_HOST_EXTRA,
                                                    user-class ) = {
        .name = "user-class",
        .description = "DHCP user class",
        .tag = DHCP_USER_CLASS_ID,
        .type = &setting_type_string,
};

/** DHCP vendor class setting */
const struct setting vendor_class_setting __setting ( SETTING_HOST_EXTRA,
                                                      vendor-class ) = {
        .name = "vendor-class",
        .description = "DHCP vendor class",
        .tag = DHCP_VENDOR_CLASS_ID,
        .type = &setting_type_string,
};

/******************************************************************************
 *
 * Built-in settings block
 *
 ******************************************************************************
 */

/** Built-in setting scope */
const struct settings_scope builtin_scope;

/**
 * Fetch error number setting
 *
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int errno_fetch ( void *data, size_t len ) {
        uint32_t content;

        /* Return current error */
        content = htonl ( errno );
        if ( len > sizeof ( content ) )
                len = sizeof ( content );
        memcpy ( data, &content, len );
        return sizeof ( content );
}

/** Error number setting */
const struct setting errno_setting __setting ( SETTING_MISC, errno ) = {
        .name = "errno",
        .description = "Last error",
        .type = &setting_type_uint32,
        .scope = &builtin_scope,
};

/** Error number built-in setting */
struct builtin_setting errno_builtin_setting __builtin_setting = {
        .setting = &errno_setting,
        .fetch = errno_fetch,
};

/**
 * Fetch build architecture setting
 *
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int buildarch_fetch ( void *data, size_t len ) {
        static const char buildarch[] = _S2 ( ARCH );

        strncpy ( data, buildarch, len );
        return ( sizeof ( buildarch ) - 1 /* NUL */ );
}

/** Build architecture setting */
const struct setting buildarch_setting __setting ( SETTING_MISC, buildarch ) = {
        .name = "buildarch",
        .description = "Build architecture",
        .type = &setting_type_string,
        .scope = &builtin_scope,
};

/** Build architecture built-in setting */
struct builtin_setting buildarch_builtin_setting __builtin_setting = {
        .setting = &buildarch_setting,
        .fetch = buildarch_fetch,
};

/**
 * Fetch platform setting
 *
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int platform_fetch ( void *data, size_t len ) {
        static const char platform[] = _S2 ( PLATFORM );

        strncpy ( data, platform, len );
        return ( sizeof ( platform ) - 1 /* NUL */ );
}

/** Platform setting */
const struct setting platform_setting __setting ( SETTING_MISC, platform ) = {
        .name = "platform",
        .description = "Platform",
        .type = &setting_type_string,
        .scope = &builtin_scope,
};

/** Platform built-in setting */
struct builtin_setting platform_builtin_setting __builtin_setting = {
        .setting = &platform_setting,
        .fetch = platform_fetch,
};

/**
 * Fetch version setting
 *
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int version_fetch ( void *data, size_t len ) {
        strncpy ( data, product_version, len );
        return ( strlen ( product_version ) );
}

/** Version setting */
const struct setting version_setting __setting ( SETTING_MISC, version ) = {
        .name = "version",
        .description = "Version",
        .type = &setting_type_string,
        .scope = &builtin_scope,
};

/** Version built-in setting */
struct builtin_setting version_builtin_setting __builtin_setting = {
        .setting = &version_setting,
        .fetch = version_fetch,
};

/**
 * Fetch current time setting
 *
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int unixtime_fetch ( void *data, size_t len ) {
        uint32_t content;

        /* Return current time */
        content = htonl ( time(NULL) );
        if ( len > sizeof ( content ) )
                len = sizeof ( content );
        memcpy ( data, &content, len );
        return sizeof ( content );
}

/** Current time setting */
const struct setting unixtime_setting __setting ( SETTING_MISC, unixtime ) = {
        .name = "unixtime",
        .description = "Seconds since the Epoch",
        .type = &setting_type_uint32,
        .scope = &builtin_scope,
};

/** Current time built-in setting */
struct builtin_setting unixtime_builtin_setting __builtin_setting = {
        .setting = &unixtime_setting,
        .fetch = unixtime_fetch,
};

/**
 * Fetch current working URI-related setting
 *
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @v rel               Relative URI string
 * @ret len             Length of setting data, or negative error
 */
static int cwuri_fetch_uri ( void *data, size_t len, const char *rel ) {
        struct uri *reluri;
        struct uri *uri;
        char *uristring;
        int ret;

        /* Check that current working URI is set */
        if ( ! cwuri ) {
                ret = -ENOENT;
                goto err_unset;
        }

        /* Construct relative URI */
        reluri = parse_uri ( rel );
        if ( ! reluri ) {
                ret = -ENOMEM;
                goto err_parse;
        }

        /* Construct resolved URI */
        uri = resolve_uri ( cwuri, reluri );
        if ( ! uri ) {
                ret = -ENOMEM;
                goto err_resolve;
        }

        /* Format URI string into allocated buffer (with NUL) */
        uristring = format_uri_alloc ( uri );
        if ( ! uristring ) {
                ret = -ENOMEM;
                goto err_format;
        }

        /* Copy URI string to buffer */
        strncpy ( data, uristring, len );
        ret = strlen ( uristring );

        free ( uristring );
 err_format:
        uri_put ( uri );
 err_resolve:
        uri_put ( reluri );
 err_parse:
 err_unset:
        return ret;
}

/**
 * Fetch current working URI setting
 *
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int cwuri_fetch ( void *data, size_t len ) {

        return cwuri_fetch_uri ( data, len, "" );
}

/**
 * Fetch current working directory URI setting
 *
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int cwduri_fetch ( void *data, size_t len ) {

        return cwuri_fetch_uri ( data, len, "." );
}

/** Current working URI setting */
const struct setting cwuri_setting __setting ( SETTING_MISC, cwuri ) = {
        .name = "cwuri",
        .description = "Current working URI",
        .type = &setting_type_string,
        .scope = &builtin_scope,
};

/** Current working directory URI setting */
const struct setting cwduri_setting __setting ( SETTING_MISC, cwduri ) = {
        .name = "cwduri",
        .description = "Current working directory URI",
        .type = &setting_type_string,
        .scope = &builtin_scope,
};

/** Current working URI built-in setting */
struct builtin_setting cwuri_builtin_setting __builtin_setting = {
        .setting = &cwuri_setting,
        .fetch = cwuri_fetch,
};

/** Current working directory URI built-in setting */
struct builtin_setting cwduri_builtin_setting __builtin_setting = {
        .setting = &cwduri_setting,
        .fetch = cwduri_fetch,
};

/**
 * Fetch built-in setting
 *
 * @v settings          Settings block
 * @v setting           Setting to fetch
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int builtin_fetch ( struct settings *settings __unused,
                           struct setting *setting,
                           void *data, size_t len ) {
        struct builtin_setting *builtin;

        for_each_table_entry ( builtin, BUILTIN_SETTINGS ) {
                if ( setting_cmp ( setting, builtin->setting ) == 0 )
                        return builtin->fetch ( data, len );
        }
        return -ENOENT;
}

/**
 * Check applicability of built-in setting
 *
 * @v settings          Settings block
 * @v setting           Setting
 * @ret applies         Setting applies within this settings block
 */
static int builtin_applies ( struct settings *settings __unused,
                             const struct setting *setting ) {

        return ( setting->scope == &builtin_scope );
}

/** Built-in settings operations */
static struct settings_operations builtin_settings_operations = {
        .applies = builtin_applies,
        .fetch = builtin_fetch,
};

/** Built-in settings */
static struct settings builtin_settings = {
        .refcnt = NULL,
        .siblings = LIST_HEAD_INIT ( builtin_settings.siblings ),
        .children = LIST_HEAD_INIT ( builtin_settings.children ),
        .op = &builtin_settings_operations,
};

/** Initialise built-in settings */
static void builtin_init ( void ) {
        int rc;

        if ( ( rc = register_settings ( &builtin_settings, NULL,
                                        "builtin" ) ) != 0 ) {
                DBG ( "Could not register built-in settings: %s\n",
                      strerror ( rc ) );
                return;
        }
}

/** Built-in settings initialiser */
struct init_fn builtin_init_fn __init_fn ( INIT_NORMAL ) = {
        .initialise = builtin_init,
};