source: bootcd/isolinux/syslinux-6.03/gpxe/src/core/iobuf.c

/*
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <errno.h>
#include <gpxe/malloc.h>
#include <gpxe/iobuf.h>

/** @file
 *
 * I/O buffers
 *
 */

/**
 * Allocate I/O buffer
 *
 * @v len       Required length of buffer
 * @ret iobuf   I/O buffer, or NULL if none available
 *
 * The I/O buffer will be physically aligned to a multiple of
 * @c IOBUF_SIZE.
 */
struct io_buffer * alloc_iob ( size_t len ) {
        struct io_buffer *iobuf = NULL;
        void *data;

        /* Pad to minimum length */
        if ( len < IOB_ZLEN )
                len = IOB_ZLEN;

        /* Align buffer length */
        len = ( len + __alignof__( *iobuf ) - 1 ) &
                ~( __alignof__( *iobuf ) - 1 );
        
        /* Allocate memory for buffer plus descriptor */
        data = malloc_dma ( len + sizeof ( *iobuf ), IOB_ALIGN );
        if ( ! data )
                return NULL;

        iobuf = ( struct io_buffer * ) ( data + len );
        iobuf->head = iobuf->data = iobuf->tail = data;
        iobuf->end = iobuf;
        return iobuf;
}

/**
 * Free I/O buffer
 *
 * @v iobuf     I/O buffer
 */
void free_iob ( struct io_buffer *iobuf ) {
        if ( iobuf ) {
                assert ( iobuf->head <= iobuf->data );
                assert ( iobuf->data <= iobuf->tail );
                assert ( iobuf->tail <= iobuf->end );
                free_dma ( iobuf->head,
                           ( iobuf->end - iobuf->head ) + sizeof ( *iobuf ) );
        }
}

/**
 * Ensure I/O buffer has sufficient headroom
 *
 * @v iobuf     I/O buffer
 * @v len       Required headroom
 *
 * This function currently only checks for the required headroom; it
 * does not reallocate the I/O buffer if required.  If we ever have a
 * code path that requires this functionality, it's a fairly trivial
 * change to make.
 */
int iob_ensure_headroom ( struct io_buffer *iobuf, size_t len ) {

        if ( iob_headroom ( iobuf ) >= len )
                return 0;
        return -ENOBUFS;
}