format_gsm.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2005, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */
 
/*! \file
 *
 * \brief Save to raw, headerless GSM data.
 * \arg File name extension: gsm
 * \ingroup formats
 */
 
/*** MODULEINFO
    <support_level>core</support_level>
 ***/
 
#include "asterisk.h"
 
#include "asterisk/mod_format.h"
#include "asterisk/module.h"
#include "asterisk/endian.h"
#include "asterisk/format_cache.h"
 
#include "msgsm.h"
 
/* Some Ideas for this code came from makegsme.c by Jeffrey Chilton */
 
/* Portions of the conversion code are by guido@sienanet.it */
 
#define GSM_FRAME_SIZE  33
#define GSM_SAMPLES 160
 
/* silent gsm frame */
/* begin binary data: */
static const char gsm_silence[] = /* 33 */
{0xD8,0x20,0xA2,0xE1,0x5A,0x50,0x00,0x49,0x24,0x92,0x49,0x24,0x50,0x00,0x49
,0x24,0x92,0x49,0x24,0x50,0x00,0x49,0x24,0x92,0x49,0x24,0x50,0x00,0x49,0x24
,0x92,0x49,0x24};
/* end binary data. size = 33 bytes */
 
static struct ast_frame *gsm_read(struct ast_filestream *s, int *whennext)
{
    size_t res;
 
    AST_FRAME_SET_BUFFER(&(s->fr), s->buf, AST_FRIENDLY_OFFSET, GSM_FRAME_SIZE);
    if ((res = fread(s->fr.data.ptr, 1, GSM_FRAME_SIZE, s->f)) != GSM_FRAME_SIZE) {
        if (res) {
            ast_log(LOG_WARNING, "Short read of %s data (expected %d bytes, read %zu): %s\n",
                    ast_format_get_name(s->fr.subclass.format), GSM_FRAME_SIZE, res,
                    strerror(errno));
        }
        return NULL;
    }
    *whennext = s->fr.samples = GSM_SAMPLES;
    return &s->fr;
}
 
static int gsm_write(struct ast_filestream *fs, struct ast_frame *f)
{
    int res;
    unsigned char gsm[2*GSM_FRAME_SIZE];
 
    if (!(f->datalen % 65)) {
        /* This is in MSGSM format, need to be converted */
        int len=0;
        while(len < f->datalen) {
            conv65(f->data.ptr + len, gsm);
            if ((res = fwrite(gsm, 1, 2*GSM_FRAME_SIZE, fs->f)) != 2*GSM_FRAME_SIZE) {
                ast_log(LOG_WARNING, "Bad write (%d/66): %s\n", res, strerror(errno));
                return -1;
            }
            len += 65;
        }
    } else {
        if (f->datalen % GSM_FRAME_SIZE) {
            ast_log(LOG_WARNING, "Invalid data length, %d, should be multiple of 33\n", f->datalen);
            return -1;
        }
        if ((res = fwrite(f->data.ptr, 1, f->datalen, fs->f)) != f->datalen) {
                ast_log(LOG_WARNING, "Bad write (%d/33): %s\n", res, strerror(errno));
                return -1;
        }
    }
    return 0;
}
 
static int gsm_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
{
    off_t offset = 0, min = 0, cur, max, distance;
 
    if ((cur = ftello(fs->f)) < 0) {
        ast_log(AST_LOG_WARNING, "Unable to determine current position in g719 filestream %p: %s\n", fs, strerror(errno));
        return -1;
    }
 
    if (fseeko(fs->f, 0, SEEK_END) < 0) {
        ast_log(AST_LOG_WARNING, "Unable to seek to end of g719 filestream %p: %s\n", fs, strerror(errno));
        return -1;
    }
 
    if ((max = ftello(fs->f)) < 0) {
        ast_log(AST_LOG_WARNING, "Unable to determine max position in g719 filestream %p: %s\n", fs, strerror(errno));
        return -1;
    }
 
    /* have to fudge to frame here, so not fully to sample */
    distance = (sample_offset / GSM_SAMPLES) * GSM_FRAME_SIZE;
    if (whence == SEEK_SET) {
        offset = distance;
    } else if (whence == SEEK_CUR || whence == SEEK_FORCECUR) {
        offset = distance + cur;
    } else if (whence == SEEK_END) {
        offset = max - distance;
    }
 
    /* Always protect against seeking past the begining. */
    offset = (offset < min)?min:offset;
    if (whence != SEEK_FORCECUR) {
        offset = (offset > max)?max:offset;
    } else if (offset > max) {
        int i;
        fseeko(fs->f, 0, SEEK_END);
        for (i=0; i< (offset - max) / GSM_FRAME_SIZE; i++) {
            if (fwrite(gsm_silence, 1, GSM_FRAME_SIZE, fs->f) != GSM_FRAME_SIZE) {
                ast_log(LOG_WARNING, "fwrite() failed: %s\n", strerror(errno));
            }
        }
    }
    return fseeko(fs->f, offset, SEEK_SET);
}
 
static int gsm_trunc(struct ast_filestream *fs)
{
    int fd;
    off_t cur;
 
    if ((fd = fileno(fs->f)) < 0) {
        ast_log(AST_LOG_WARNING, "Unable to determine file descriptor for gsm filestream %p: %s\n", fs, strerror(errno));
        return -1;
    }
    if ((cur = ftello(fs->f)) < 0) {
        ast_log(AST_LOG_WARNING, "Unable to determine current position in gsm filestream %p: %s\n", fs, strerror(errno));
        return -1;
    }
    /* Truncate file to current length */
    return ftruncate(fd, cur);
}
 
static off_t gsm_tell(struct ast_filestream *fs)
{
    off_t offset = ftello(fs->f);
 
    if (offset < 0) {
        ast_log(AST_LOG_WARNING, "Unable to determine offset for gsm filestream %p: %s\n", fs, strerror(errno));
        return 0;
    }
 
    return (offset / GSM_FRAME_SIZE) * GSM_SAMPLES;
}
 
static struct ast_format_def gsm_f = {
    .name = "gsm",
    .exts = "gsm",
    .mime_types = "audio/gsm",
    .write = gsm_write,
    .seek = gsm_seek,
    .trunc = gsm_trunc,
    .tell = gsm_tell,
    .read = gsm_read,
    .buf_size = 2*GSM_FRAME_SIZE + AST_FRIENDLY_OFFSET, /* 2 gsm frames */
};
 
static int load_module(void)
{
    gsm_f.format = ast_format_gsm;
    if (ast_format_def_register(&gsm_f))
        return AST_MODULE_LOAD_DECLINE;
    return AST_MODULE_LOAD_SUCCESS;
}
 
static int unload_module(void)
{
    return ast_format_def_unregister(gsm_f.name);
}
 
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Raw GSM data",
    .support_level = AST_MODULE_SUPPORT_CORE,
    .load = load_module,
    .unload = unload_module,
    .load_pri = AST_MODPRI_APP_DEPEND
);