posix_io.c

Go to the documentation of this file.

/*
 * Copyright (C) 2007 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 <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ipxe/list.h>
#include <ipxe/iobuf.h>
#include <ipxe/xfer.h>
#include <ipxe/open.h>
#include <ipxe/process.h>
#include <ipxe/posix_io.h>

/** @file
 *
 * POSIX-like I/O
 *
 * These functions provide traditional blocking I/O semantics.  They
 * are designed to be used by the PXE TFTP API.  Because they block,
 * they may not be used by most other portions of the iPXE codebase.
 */

/** An open file */
struct posix_file {
        /** Reference count for this object */
        struct refcnt refcnt;
        /** List of open files */
        struct list_head list;
        /** File descriptor */
        int fd;
        /** Overall status
         *
         * Set to -EINPROGRESS while data transfer is in progress.
         */
        int rc;
        /** Data transfer interface */
        struct interface xfer;
        /** Current seek position */
        size_t pos;
        /** File size */
        size_t filesize;
        /** Received data queue */
        struct list_head data;
};

/** List of open files */
static LIST_HEAD ( posix_files );

/**
 * Free open file
 *
 * @v refcnt            Reference counter
 */
static void posix_file_free ( struct refcnt *refcnt ) {
        struct posix_file *file =
                container_of ( refcnt, struct posix_file, refcnt );
        struct io_buffer *iobuf;
        struct io_buffer *tmp;

        list_for_each_entry_safe ( iobuf, tmp, &file->data, list ) {
                list_del ( &iobuf->list );
                free_iob ( iobuf );
        }
        free ( file );
}

/**
 * Terminate file data transfer
 *
 * @v file              POSIX file
 * @v rc                Reason for termination
 */
static void posix_file_finished ( struct posix_file *file, int rc ) {
        intf_shutdown ( &file->xfer, rc );
        file->rc = rc;
}

/**
 * Handle deliver_iob() event
 *
 * @v file              POSIX file
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int posix_file_xfer_deliver ( struct posix_file *file,
                                     struct io_buffer *iobuf,
                                     struct xfer_metadata *meta ) {

        /* Keep track of file position solely for the filesize */
        if ( meta->flags & XFER_FL_ABS_OFFSET )
                file->pos = 0;
        file->pos += meta->offset;
        if ( file->filesize < file->pos )
                file->filesize = file->pos;

        if ( iob_len ( iobuf ) ) {
                list_add_tail ( &iobuf->list, &file->data );
        } else {
                free_iob ( iobuf );
        }

        return 0;
}

/** POSIX file data transfer interface operations */
static struct interface_operation posix_file_xfer_operations[] = {
        INTF_OP ( xfer_deliver, struct posix_file *, posix_file_xfer_deliver ),
        INTF_OP ( intf_close, struct posix_file *, posix_file_finished ),
};

/** POSIX file data transfer interface descriptor */
static struct interface_descriptor posix_file_xfer_desc =
        INTF_DESC ( struct posix_file, xfer, posix_file_xfer_operations );

/**
 * Identify file by file descriptor
 *
 * @v fd                File descriptor
 * @ret file            Corresponding file, or NULL
 */
static struct posix_file * posix_fd_to_file ( int fd ) {
        struct posix_file *file;

        list_for_each_entry ( file, &posix_files, list ) {
                if ( file->fd == fd )
                        return file;
        }
        return NULL;
}

/**
 * Find an available file descriptor
 *
 * @ret fd              File descriptor, or negative error number
 */
static int posix_find_free_fd ( void ) {
        int fd;

        for ( fd = POSIX_FD_MIN ; fd <= POSIX_FD_MAX ; fd++ ) {
                if ( ! posix_fd_to_file ( fd ) )
                        return fd;
        }
        DBG ( "POSIX could not find free file descriptor\n" );
        return -ENFILE;
}

/**
 * Open file
 *
 * @v uri_string        URI string
 * @ret fd              File descriptor, or negative error number
 */
int open ( const char *uri_string ) {
        struct posix_file *file;
        int fd;
        int rc;

        /* Find a free file descriptor to use */
        fd = posix_find_free_fd();
        if ( fd < 0 )
                return fd;

        /* Allocate and initialise structure */
        file = zalloc ( sizeof ( *file ) );
        if ( ! file )
                return -ENOMEM;
        ref_init ( &file->refcnt, posix_file_free );
        file->fd = fd;
        file->rc = -EINPROGRESS;
        intf_init ( &file->xfer, &posix_file_xfer_desc, &file->refcnt );
        INIT_LIST_HEAD ( &file->data );

        /* Open URI on data transfer interface */
        if ( ( rc = xfer_open_uri_string ( &file->xfer, uri_string ) ) != 0 )
                goto err;

        /* Wait for open to succeed or fail */
        while ( list_empty ( &file->data ) ) {
                step();
                if ( file->rc == 0 )
                        break;
                if ( file->rc != -EINPROGRESS ) {
                        rc = file->rc;
                        goto err;
                }
        }

        /* Add to list of open files.  List takes reference ownership. */
        list_add ( &file->list, &posix_files );
        DBG ( "POSIX opened %s as file %d\n", uri_string, fd );
        return fd;

 err:
        posix_file_finished ( file, rc );
        ref_put ( &file->refcnt );
        return rc;
}

/**
 * Check file descriptors for readiness
 *
 * @v readfds           File descriptors to check
 * @v wait              Wait until data is ready
 * @ret nready          Number of ready file descriptors
 */
int select ( fd_set *readfds, int wait ) {
        struct posix_file *file;
        int fd;

        do {
                for ( fd = POSIX_FD_MIN ; fd <= POSIX_FD_MAX ; fd++ ) {
                        if ( ! FD_ISSET ( fd, readfds ) )
                                continue;
                        file = posix_fd_to_file ( fd );
                        if ( ! file )
                                return -EBADF;
                        if ( ( list_empty ( &file->data ) ) &&
                             ( file->rc == -EINPROGRESS ) )
                                continue;
                        /* Data is available or status has changed */
                        FD_ZERO ( readfds );
                        FD_SET ( fd, readfds );
                        return 1;
                }
                step();
        } while ( wait );

        return 0;
}

/**
 * Read data from file
 *
 * @v buffer            Data buffer
 * @v offset            Starting offset within data buffer
 * @v len               Maximum length to read
 * @ret len             Actual length read, or negative error number
 *
 * This call is non-blocking; if no data is available to read then
 * -EWOULDBLOCK will be returned.
 */
ssize_t read_user ( int fd, userptr_t buffer, off_t offset, size_t max_len ) {
        struct posix_file *file;
        struct io_buffer *iobuf;
        size_t len;

        /* Identify file */
        file = posix_fd_to_file ( fd );
        if ( ! file )
                return -EBADF;

        /* Try to fetch more data if none available */
        if ( list_empty ( &file->data ) )
                step();

        /* Dequeue at most one received I/O buffer into user buffer */
        list_for_each_entry ( iobuf, &file->data, list ) {
                len = iob_len ( iobuf );
                if ( len > max_len )
                        len = max_len;
                copy_to_user ( buffer, offset, iobuf->data, len );
                iob_pull ( iobuf, len );
                if ( ! iob_len ( iobuf ) ) {
                        list_del ( &iobuf->list );
                        free_iob ( iobuf );
                }
                file->pos += len;
                assert ( len != 0 );
                return len;
        }

        /* If file has completed, return (after returning all data) */
        if ( file->rc != -EINPROGRESS ) {
                assert ( list_empty ( &file->data ) );
                return file->rc;
        }

        /* No data ready and file still in progress; return -WOULDBLOCK */
        return -EWOULDBLOCK;
}

/**
 * Determine file size
 *
 * @v fd                File descriptor
 * @ret size            File size, or negative error number
 */
ssize_t fsize ( int fd ) {
        struct posix_file *file;

        /* Identify file */
        file = posix_fd_to_file ( fd );
        if ( ! file )
                return -EBADF;

        return file->filesize;
}

/**
 * Close file
 *
 * @v fd                File descriptor
 * @ret rc              Return status code
 */
int close ( int fd ) {
        struct posix_file *file;

        /* Identify file */
        file = posix_fd_to_file ( fd );
        if ( ! file )
                return -EBADF;

        /* Terminate data transfer */
        posix_file_finished ( file, 0 );

        /* Remove from list of open files and drop reference */
        list_del ( &file->list );
        ref_put ( &file->refcnt );
        return 0;
}