Asterisk.org: Developer Documentation (28 Oct 2009)

Wed Oct 28 15:47:54 2009

## Asterisk developer's documentation

# format_gsm.c

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    00001 /*
    00002  * Asterisk -- An open source telephony toolkit.
    00003  *
    00004  * Copyright (C) 1999 - 2005, Digium, Inc.
    00005  *
    00006  * Mark Spencer <markster@digium.com>
    00007  *
    00008  * See http://www.asterisk.org for more information about
    00009  * the Asterisk project. Please do not directly contact
    00010  * any of the maintainers of this project for assistance;
    00011  * the project provides a web site, mailing lists and IRC
    00012  * channels for your use.
    00013  *
    00014  * This program is free software, distributed under the terms of
    00015  * the GNU General Public License Version 2. See the LICENSE file
    00016  * at the top of the source tree.
    00017  */
    00018
    00019 /*! \file
    00020  *
    00021  * \brief Save to raw, headerless GSM data.
    00022  * \arg File name extension: gsm
    00023  * \ingroup formats
    00024  */
    00025
    00026 #include <unistd.h>
    00027 #include <netinet/in.h>
    00028 #include <arpa/inet.h>
    00029 #include <stdlib.h>
    00030 #include <sys/time.h>
    00031 #include <stdio.h>
    00032 #include <errno.h>
    00033 #include <string.h>
    00034
    00035 #include "asterisk.h"
    00036
    00037 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 7221 $")
    00038
    00039 #include "asterisk/lock.h"
    00040 #include "asterisk/channel.h"
    00041 #include "asterisk/file.h"
    00042 #include "asterisk/logger.h"
    00043 #include "asterisk/sched.h"
    00044 #include "asterisk/module.h"
    00045 #include "asterisk/endian.h"
    00046
    00047 #include "msgsm.h"
    00048
    00049 /* Some Ideas for this code came from makegsme.c by Jeffrey Chilton */
    00050
    00051 /* Portions of the conversion code are by guido@sienanet.it */
    00052
    00053 /* silent gsm frame */
    00054 /* begin binary data: */
    00055 char gsm_silence[] = /* 33 */
    00056 {0xD8,0x20,0xA2,0xE1,0x5A,0x50,0x00,0x49,0x24,0x92,0x49,0x24,0x50,0x00,0x49
    00057 ,0x24,0x92,0x49,0x24,0x50,0x00,0x49,0x24,0x92,0x49,0x24,0x50,0x00,0x49,0x24
    00058 ,0x92,0x49,0x24};
    00059 /* end binary data. size = 33 bytes */
    00060
    00061 struct ast_filestream {
    00062    void *reserved[AST_RESERVED_POINTERS];
    00063    /* Believe it or not, we must decode/recode to account for the
    00064       weird MS format */
    00065    /* This is what a filestream means to us */
    00066    FILE *f; /* Descriptor */
    00067    struct ast_frame fr;          /* Frame information */
    00068    char waste[AST_FRIENDLY_OFFSET]; /* Buffer for sending frames, etc */
    00069    char empty;                   /* Empty character */
    00070    unsigned char gsm[66];           /* Two Real GSM Frames */
    00071 };
    00072
    00073
    00074 AST_MUTEX_DEFINE_STATIC(gsm_lock);
    00075 static int glistcnt = 0;
    00076
    00077 static char *name = "gsm";
    00078 static char *desc = "Raw GSM data";
    00079 static char *exts = "gsm";
    00080
    00081 static struct ast_filestream *gsm_open(FILE *f)
    00082 {
    00083    /* We don't have any header to read or anything really, but
    00084       if we did, it would go here.  We also might want to check
    00085       and be sure it's a valid file.  */
    00086    struct ast_filestream *tmp;
    00087    if ((tmp = malloc(sizeof(struct ast_filestream)))) {
    00088       memset(tmp, 0, sizeof(struct ast_filestream));
    00089       if (ast_mutex_lock(&gsm_lock)) {
    00090          ast_log(LOG_WARNING, "Unable to lock gsm list\n");
    00091          free(tmp);
    00092          return NULL;
    00093       }
    00094       tmp->f = f;
    00095       tmp->fr.data = tmp->gsm;
    00096       tmp->fr.frametype = AST_FRAME_VOICE;
    00097       tmp->fr.subclass = AST_FORMAT_GSM;
    00098       /* datalen will vary for each frame */
    00099       tmp->fr.src = name;
    00100       tmp->fr.mallocd = 0;
    00101       glistcnt++;
    00102       ast_mutex_unlock(&gsm_lock);
    00103       ast_update_use_count();
    00104    }
    00105    return tmp;
    00106 }
    00107
    00108 static struct ast_filestream *gsm_rewrite(FILE *f, const char *comment)
    00109 {
    00110    /* We don't have any header to read or anything really, but
    00111       if we did, it would go here.  We also might want to check
    00112       and be sure it's a valid file.  */
    00113    struct ast_filestream *tmp;
    00114    if ((tmp = malloc(sizeof(struct ast_filestream)))) {
    00115       memset(tmp, 0, sizeof(struct ast_filestream));
    00116       if (ast_mutex_lock(&gsm_lock)) {
    00117          ast_log(LOG_WARNING, "Unable to lock gsm list\n");
    00118          free(tmp);
    00119          return NULL;
    00120       }
    00121       tmp->f = f;
    00122       glistcnt++;
    00123       ast_mutex_unlock(&gsm_lock);
    00124       ast_update_use_count();
    00125    } else
    00126       ast_log(LOG_WARNING, "Out of memory\n");
    00127    return tmp;
    00128 }
    00129
    00130 static void gsm_close(struct ast_filestream *s)
    00131 {
    00132    if (ast_mutex_lock(&gsm_lock)) {
    00133       ast_log(LOG_WARNING, "Unable to lock gsm list\n");
    00134       return;
    00135    }
    00136    glistcnt--;
    00137    ast_mutex_unlock(&gsm_lock);
    00138    ast_update_use_count();
    00139    fclose(s->f);
    00140    free(s);
    00141 }
    00142
    00143 static struct ast_frame *gsm_read(struct ast_filestream *s, int *whennext)
    00144 {
    00145    int res;
    00146    s->fr.frametype = AST_FRAME_VOICE;
    00147    s->fr.subclass = AST_FORMAT_GSM;
    00148    s->fr.offset = AST_FRIENDLY_OFFSET;
    00149    s->fr.samples = 160;
    00150    s->fr.datalen = 33;
    00151    s->fr.mallocd = 0;
    00152    s->fr.data = s->gsm;
    00153    if ((res = fread(s->gsm, 1, 33, s->f)) != 33) {
    00154       if (res)
    00155          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
    00156       return NULL;
    00157    }
    00158    *whennext = 160;
    00159    return &s->fr;
    00160 }
    00161
    00162 static int gsm_write(struct ast_filestream *fs, struct ast_frame *f)
    00163 {
    00164    int res;
    00165    unsigned char gsm[66];
    00166    if (f->frametype != AST_FRAME_VOICE) {
    00167       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
    00168       return -1;
    00169    }
    00170    if (f->subclass != AST_FORMAT_GSM) {
    00171       ast_log(LOG_WARNING, "Asked to write non-GSM frame (%d)!\n", f->subclass);
    00172       return -1;
    00173    }
    00174    if (!(f->datalen % 65)) {
    00175       /* This is in MSGSM format, need to be converted */
    00176       int len=0;
    00177       while(len < f->datalen) {
    00178          conv65(f->data + len, gsm);
    00179          if ((res = fwrite(gsm, 1, 66, fs->f)) != 66) {
    00180             ast_log(LOG_WARNING, "Bad write (%d/66): %s\n", res, strerror(errno));
    00181             return -1;
    00182          }
    00183          len += 65;
    00184       }
    00185    } else {
    00186       if (f->datalen % 33) {
    00187          ast_log(LOG_WARNING, "Invalid data length, %d, should be multiple of 33\n", f->datalen);
    00188          return -1;
    00189       }
    00190       if ((res = fwrite(f->data, 1, f->datalen, fs->f)) != f->datalen) {
    00191             ast_log(LOG_WARNING, "Bad write (%d/33): %s\n", res, strerror(errno));
    00192             return -1;
    00193       }
    00194    }
    00195    return 0;
    00196 }
    00197
    00198 static int gsm_seek(struct ast_filestream *fs, long sample_offset, int whence)
    00199 {
    00200    off_t offset=0,min,cur,max,distance;
    00201
    00202    min = 0;
    00203    cur = ftell(fs->f);
    00204    fseek(fs->f, 0, SEEK_END);
    00205    max = ftell(fs->f);
    00206    /* have to fudge to frame here, so not fully to sample */
    00207    distance = (sample_offset/160) * 33;
    00208    if(whence == SEEK_SET)
    00209       offset = distance;
    00210    else if(whence == SEEK_CUR || whence == SEEK_FORCECUR)
    00211       offset = distance + cur;
    00212    else if(whence == SEEK_END)
    00213       offset = max - distance;
    00214    /* Always protect against seeking past the begining. */
    00215    offset = (offset < min)?min:offset;
    00216    if (whence != SEEK_FORCECUR) {
    00217       offset = (offset > max)?max:offset;
    00218    } else if (offset > max) {
    00219       int i;
    00220       fseek(fs->f, 0, SEEK_END);
    00221       for (i=0; i< (offset - max) / 33; i++) {
    00222          fwrite(gsm_silence, 1, 33, fs->f);
    00223       }
    00224    }
    00225    return fseek(fs->f, offset, SEEK_SET);
    00226 }
    00227
    00228 static int gsm_trunc(struct ast_filestream *fs)
    00229 {
    00230    return ftruncate(fileno(fs->f), ftell(fs->f));
    00231 }
    00232
    00233 static long gsm_tell(struct ast_filestream *fs)
    00234 {
    00235    off_t offset;
    00236    offset = ftell(fs->f);
    00237    return (offset/33)*160;
    00238 }
    00239
    00240 static char *gsm_getcomment(struct ast_filestream *s)
    00241 {
    00242    return NULL;
    00243 }
    00244
    00245 int load_module()
    00246 {
    00247    return ast_format_register(name, exts, AST_FORMAT_GSM,
    00248                         gsm_open,
    00249                         gsm_rewrite,
    00250                         gsm_write,
    00251                         gsm_seek,
    00252                         gsm_trunc,
    00253                         gsm_tell,
    00254                         gsm_read,
    00255                         gsm_close,
    00256                         gsm_getcomment);
    00257
    00258
    00259 }
    00260
    00261 int unload_module()
    00262 {
    00263    return ast_format_unregister(name);
    00264 }
    00265
    00266 int usecount()
    00267 {
    00268    return glistcnt;
    00269 }
    00270
    00271 char *description()
    00272 {
    00273    return desc;
    00274 }
    00275
    00276
    00277 char *key()
    00278 {
    00279    return ASTERISK_GPL_KEY;
    00280 }