readline.c

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/*
 * Copyright (C) 2006 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 <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <ipxe/console.h>
#include <ipxe/keys.h>
#include <ipxe/editstring.h>
#include <readline/readline.h>

/** @file
 *
 * Minimal readline
 *
 */

/**
 * Synchronise console with edited string
 *
 * @v string            Editable string
 */
static void sync_console ( struct edit_string *string ) {
        unsigned int mod_start = string->mod_start;
        unsigned int mod_end = string->mod_end;
        unsigned int cursor = string->last_cursor;
        const char *buf = *(string->buf);
        size_t len = strlen ( buf );

        /* Expand region back to old cursor position if applicable */
        if ( mod_start > string->last_cursor )
                mod_start = string->last_cursor;

        /* Expand region forward to new cursor position if applicable */
        if ( mod_end < string->cursor )
                mod_end = string->cursor;

        /* Backspace to start of region */
        while ( cursor > mod_start ) {
                putchar ( '\b' );
                cursor--;
        }

        /* Print modified region */
        while ( cursor < mod_end ) {
                putchar ( ( cursor >= len ) ? ' ' : buf[cursor] );
                cursor++;
        }

        /* Backspace to new cursor position */
        while ( cursor > string->cursor ) {
                putchar ( '\b' );
                cursor--;
        }
}

/**
 * Locate history entry
 *
 * @v history           History buffer
 * @v depth             Depth within history buffer
 * @ret entry           History entry
 */
static struct readline_history_entry *
history_entry ( struct readline_history *history, unsigned int depth ) {
        unsigned int offset;

        offset = ( ( history->next - depth ) %
                   ( sizeof ( history->entries ) /
                     sizeof ( history->entries[0] ) ) );
        return &history->entries[offset];
}

/**
 * Read string from history buffer
 *
 * @v history           History buffer
 * @v depth             Depth within history buffer
 * @ret string          String
 */
static const char * history_fetch ( struct readline_history *history,
                                    unsigned int depth ) {
        struct readline_history_entry *entry;

        /* Return the temporary copy if it exists, otherwise return
         * the persistent copy.
         */
        entry = history_entry ( history, depth );
        return ( entry->temp ? entry->temp : entry->string );
}

/**
 * Write temporary string copy to history buffer
 *
 * @v history           History buffer
 * @v depth             Depth within history buffer
 * @v string            String
 */
static void history_store ( struct readline_history *history,
                            unsigned int depth, const char *string ) {
        struct readline_history_entry *entry;
        char *temp;

        /* Create temporary copy of string */
        temp = strdup ( string );
        if ( ! temp ) {
                /* Just discard the string; there's nothing we can do */
                DBGC ( history, "READLINE %p could not store string\n",
                       history );
                return;
        }

        /* Store temporary copy */
        entry = history_entry ( history, depth );
        free ( entry->temp );
        entry->temp = temp;
}

/**
 * Move to new history depth
 *
 * @v history           History buffer
 * @v offset            Offset by which to change depth
 * @v old_string        String (possibly modified) at current depth
 * @ret new_string      String at new depth, or NULL for no movement
 */
static const char * history_move ( struct readline_history *history,
                                   int offset, const char *old_string ) {
        unsigned int new_depth = ( history->depth + offset );
        const char * new_string = history_fetch ( history, new_depth );

        /* Depth checks */
        if ( new_depth > READLINE_HISTORY_MAX_DEPTH )
                return NULL;
        if ( ! new_string )
                return NULL;

        /* Store temporary copy of old string at current depth */
        history_store ( history, history->depth, old_string );

        /* Update depth */
        history->depth = new_depth;

        /* Return new string */
        return new_string;
}

/**
 * Append new history entry
 *
 * @v history           History buffer
 * @v string            String
 */
static void history_append ( struct readline_history *history,
                             const char *string ) {
        struct readline_history_entry *entry;

        /* Store new entry */
        entry = history_entry ( history, 0 );
        assert ( entry->string == NULL );
        entry->string = strdup ( string );
        if ( ! entry->string ) {
                /* Just discard the string; there's nothing we can do */
                DBGC ( history, "READLINE %p could not append string\n",
                       history );
                return;
        }

        /* Increment history position */
        history->next++;

        /* Prepare empty "next" slot */
        entry = history_entry ( history, 0 );
        free ( entry->string );
        entry->string = NULL;
}

/**
 * Clean up history after editing
 *
 * @v history           History buffer
 */
static void history_cleanup ( struct readline_history *history ) {
        struct readline_history_entry *entry;
        unsigned int i;

        /* Discard any temporary strings */
        for ( i = 0 ; i < ( sizeof ( history->entries ) /
                            sizeof ( history->entries[0] ) ) ; i++ ) {
                entry = &history->entries[i];
                free ( entry->temp );
                entry->temp = NULL;
        }

        /* Reset depth */
        history->depth = 0;

        /* Sanity check */
        entry = history_entry ( history, 0 );
        assert ( entry->string == NULL );
}

/**
 * Free history buffer
 *
 * @v history           History buffer
 */
void history_free ( struct readline_history *history ) {
        struct readline_history_entry *entry;
        unsigned int i;

        /* Discard any temporary strings */
        for ( i = 0 ; i < ( sizeof ( history->entries ) /
                            sizeof ( history->entries[0] ) ) ; i++ ) {
                entry = &history->entries[i];
                assert ( entry->temp == NULL );
                free ( entry->string );
        }
}

/**
 * Read line from console (with history)
 *
 * @v prompt            Prompt string
 * @v prefill           Prefill string, or NULL for no prefill
 * @v history           History buffer, or NULL for no history
 * @v timeout           Timeout period, in ticks (0=indefinite)
 * @ret line            Line read from console (excluding terminating newline)
 * @ret rc              Return status code
 *
 * The returned line is allocated with malloc(); the caller must
 * eventually call free() to release the storage.
 */
int readline_history ( const char *prompt, const char *prefill,
                       struct readline_history *history, unsigned long timeout,
                       char **line ) {
        struct edit_string string;
        int key;
        int move_by;
        const char *new_string;
        int rc;

        /* Display prompt, if applicable */
        if ( prompt )
                printf ( "%s", prompt );

        /* Ensure cursor is visible */
        printf ( "\033[?25h" );

        /* Initialise editable string */
        *line = NULL;
        memset ( &string, 0, sizeof ( string ) );
        init_editstring ( &string, line );

        /* Prefill string */
        if ( ( rc = replace_string ( &string, prefill ) ) != 0 )
                goto error;
        sync_console ( &string );

        while ( 1 ) {

                /* Get keypress */
                key = getkey ( timeout );
                if ( key < 0 ) {
                        rc = -ETIMEDOUT;
                        goto error;
                }
                timeout = 0;

                /* Handle keypress */
                key = edit_string ( &string, key );
                sync_console ( &string );
                move_by = 0;
                switch ( key ) {
                case CR:
                case LF:
                        rc = 0;
                        goto done;
                case CTRL_C:
                        rc = -ECANCELED;
                        goto error;
                case KEY_UP:
                        move_by = 1;
                        break;
                case KEY_DOWN:
                        move_by = -1;
                        break;
                default:
                        /* Do nothing for unrecognised keys or edit errors */
                        break;
                }

                /* Handle history movement, if applicable */
                if ( move_by && history ) {
                        new_string = history_move ( history, move_by, *line );
                        if ( new_string ) {
                                replace_string ( &string, new_string );
                                sync_console ( &string );
                        }
                }
        }

 error:
        free ( *line );
        *line = NULL;
 done:
        putchar ( '\n' );
        if ( history ) {
                if ( *line && (*line)[0] )
                        history_append ( history, *line );
                history_cleanup ( history );
        }
        assert ( ( rc == 0 ) ^ ( *line == NULL ) );
        return rc;
}

/**
 * Read line from console
 *
 * @v prompt            Prompt string
 * @ret line            Line read from console (excluding terminating newline)
 *
 * The returned line is allocated with malloc(); the caller must
 * eventually call free() to release the storage.
 */
char * readline ( const char *prompt ) {
        char *line;

        readline_history ( prompt, NULL, NULL, 0, &line );
        return line;
}