Asterisk.org: Developer Documentation (28 Oct 2009)

Wed Oct 28 15:47:54 2009

## Asterisk developer's documentation

# format_pcm_alaw.c

Go to the documentation of this file.

    00001 /*
    00002  * Asterisk -- An open source telephony toolkit.
    00003  *
    00004  * Copyright (C) 1999 - 2006, 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 Flat, binary, alaw PCM file format.
    00022  * \arg File name extensions: alaw, al
    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 <sys/times.h>
    00032 #include <sys/types.h>
    00033 #include <stdio.h>
    00034 #include <errno.h>
    00035 #include <string.h>
    00036
    00037 #include "asterisk.h"
    00038
    00039 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 7819 $")
    00040
    00041 #include "asterisk/lock.h"
    00042 #include "asterisk/channel.h"
    00043 #include "asterisk/file.h"
    00044 #include "asterisk/logger.h"
    00045 #include "asterisk/sched.h"
    00046 #include "asterisk/module.h"
    00047 #include "asterisk/endian.h"
    00048 #include "asterisk/alaw.h"
    00049
    00050 #define BUF_SIZE 160    /* 160 samples */
    00051
    00052 /* #define REALTIME_WRITE */
    00053
    00054 struct ast_filestream {
    00055    void *reserved[AST_RESERVED_POINTERS];
    00056    /* Believe it or not, we must decode/recode to account for the
    00057       weird MS format */
    00058    /* This is what a filestream means to us */
    00059    FILE *f; /* Descriptor */
    00060    struct ast_frame fr;          /* Frame information */
    00061    char waste[AST_FRIENDLY_OFFSET]; /* Buffer for sending frames, etc */
    00062    char empty;                   /* Empty character */
    00063    unsigned char buf[BUF_SIZE];           /* Output Buffer */
    00064 #ifdef REALTIME_WRITE
    00065    unsigned long start_time;
    00066 #endif
    00067 };
    00068
    00069
    00070 AST_MUTEX_DEFINE_STATIC(pcm_lock);
    00071 static int glistcnt = 0;
    00072
    00073 static char *name = "alaw";
    00074 static char *desc = "Raw aLaw 8khz PCM Audio support";
    00075 static char *exts = "alaw|al";
    00076
    00077 static char alaw_silence[BUF_SIZE];
    00078
    00079
    00080 #if 0
    00081 /* Returns time in msec since system boot. */
    00082 static unsigned long get_time(void)
    00083 {
    00084    struct tms buf;
    00085    clock_t cur;
    00086
    00087    cur = times( &buf );
    00088    if( cur < 0 )
    00089    {
    00090       ast_log( LOG_WARNING, "Cannot get current time\n" );
    00091       return 0;
    00092    }
    00093    return cur * 1000 / sysconf( _SC_CLK_TCK );
    00094 }
    00095 #endif
    00096
    00097 static struct ast_filestream *pcm_open(FILE *f)
    00098 {
    00099    /* We don't have any header to read or anything really, but
    00100       if we did, it would go here.  We also might want to check
    00101       and be sure it's a valid file.  */
    00102    struct ast_filestream *tmp;
    00103    if ((tmp = malloc(sizeof(struct ast_filestream)))) {
    00104       memset(tmp, 0, sizeof(struct ast_filestream));
    00105       if (ast_mutex_lock(&pcm_lock)) {
    00106          ast_log(LOG_WARNING, "Unable to lock pcm list\n");
    00107          free(tmp);
    00108          return NULL;
    00109       }
    00110       tmp->f = f;
    00111       tmp->fr.data = tmp->buf;
    00112       tmp->fr.frametype = AST_FRAME_VOICE;
    00113       tmp->fr.subclass = AST_FORMAT_ALAW;
    00114       /* datalen will vary for each frame */
    00115       tmp->fr.src = name;
    00116       tmp->fr.mallocd = 0;
    00117 #ifdef REALTIME_WRITE
    00118       tmp->start_time = get_time();
    00119 #endif
    00120       glistcnt++;
    00121       ast_mutex_unlock(&pcm_lock);
    00122       ast_update_use_count();
    00123    }
    00124    return tmp;
    00125 }
    00126
    00127 static struct ast_filestream *pcm_rewrite(FILE *f, const char *comment)
    00128 {
    00129    /* We don't have any header to read or anything really, but
    00130       if we did, it would go here.  We also might want to check
    00131       and be sure it's a valid file.  */
    00132    struct ast_filestream *tmp;
    00133    if ((tmp = malloc(sizeof(struct ast_filestream)))) {
    00134       memset(tmp, 0, sizeof(struct ast_filestream));
    00135       if (ast_mutex_lock(&pcm_lock)) {
    00136          ast_log(LOG_WARNING, "Unable to lock pcm list\n");
    00137          free(tmp);
    00138          return NULL;
    00139       }
    00140       tmp->f = f;
    00141 #ifdef REALTIME_WRITE
    00142       tmp->start_time = get_time();
    00143 #endif
    00144       glistcnt++;
    00145       ast_mutex_unlock(&pcm_lock);
    00146       ast_update_use_count();
    00147    } else
    00148       ast_log(LOG_WARNING, "Out of memory\n");
    00149    return tmp;
    00150 }
    00151
    00152 static void pcm_close(struct ast_filestream *s)
    00153 {
    00154    if (ast_mutex_lock(&pcm_lock)) {
    00155       ast_log(LOG_WARNING, "Unable to lock pcm list\n");
    00156       return;
    00157    }
    00158    glistcnt--;
    00159    ast_mutex_unlock(&pcm_lock);
    00160    ast_update_use_count();
    00161    fclose(s->f);
    00162    free(s);
    00163    s = NULL;
    00164 }
    00165
    00166 static struct ast_frame *pcm_read(struct ast_filestream *s, int *whennext)
    00167 {
    00168    int res;
    00169    /* Send a frame from the file to the appropriate channel */
    00170
    00171    s->fr.frametype = AST_FRAME_VOICE;
    00172    s->fr.subclass = AST_FORMAT_ALAW;
    00173    s->fr.offset = AST_FRIENDLY_OFFSET;
    00174    s->fr.mallocd = 0;
    00175    s->fr.data = s->buf;
    00176    if ((res = fread(s->buf, 1, BUF_SIZE, s->f)) < 1) {
    00177       if (res)
    00178          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
    00179       return NULL;
    00180    }
    00181    s->fr.samples = res;
    00182    s->fr.datalen = res;
    00183    *whennext = s->fr.samples;
    00184    return &s->fr;
    00185 }
    00186
    00187 static int pcm_write(struct ast_filestream *fs, struct ast_frame *f)
    00188 {
    00189    int res;
    00190 #ifdef REALTIME_WRITE
    00191    unsigned long cur_time;
    00192    unsigned long fpos;
    00193    struct stat stat_buf;
    00194 #endif
    00195
    00196    if (f->frametype != AST_FRAME_VOICE) {
    00197       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
    00198       return -1;
    00199    }
    00200    if (f->subclass != AST_FORMAT_ALAW) {
    00201       ast_log(LOG_WARNING, "Asked to write non-alaw frame (%d)!\n", f->subclass);
    00202       return -1;
    00203    }
    00204
    00205 #ifdef REALTIME_WRITE
    00206    cur_time = get_time();
    00207    fpos = ( cur_time - fs->start_time ) * 8; /* 8 bytes per msec */
    00208    /* Check if we have written to this position yet. If we have, then increment pos by one frame
    00209    *  for some degree of protection against receiving packets in the same clock tick.
    00210    */
    00211
    00212    fstat(fileno(fs->f), &stat_buf );
    00213    if (stat_buf.st_size > fpos ) {
    00214       fpos += f->datalen;  /* Incrementing with the size of this current frame */
    00215    }
    00216
    00217    if (stat_buf.st_size < fpos) {
    00218       /* fill the gap with 0x55 rather than 0. */
    00219       char buf[ 512 ];
    00220       unsigned long cur, to_write;
    00221
    00222       cur = stat_buf.st_size;
    00223       if (fseek(fs->f, cur, SEEK_SET) < 0) {
    00224          ast_log( LOG_WARNING, "Cannot seek in file: %s\n", strerror(errno) );
    00225          return -1;
    00226       }
    00227       memset(buf, 0x55, 512);
    00228       while (cur < fpos) {
    00229          to_write = fpos - cur;
    00230          if (to_write > 512) {
    00231             to_write = 512;
    00232          }
    00233          fwrite(buf, 1, to_write, fs->f);
    00234          cur += to_write;
    00235       }
    00236    }
    00237
    00238
    00239    if (fseek(s->f, fpos, SEEK_SET) < 0) {
    00240       ast_log( LOG_WARNING, "Cannot seek in file: %s\n", strerror(errno) );
    00241       return -1;
    00242    }
    00243 #endif   /* REALTIME_WRITE */
    00244
    00245    if ((res = fwrite(f->data, 1, f->datalen, fs->f)) != f->datalen) {
    00246          ast_log(LOG_WARNING, "Bad write (%d/%d): %s\n", res, f->datalen, strerror(errno));
    00247          return -1;
    00248    }
    00249    return 0;
    00250 }
    00251
    00252 static int pcm_seek(struct ast_filestream *fs, long sample_offset, int whence)
    00253 {
    00254    long cur, max, offset = 0;
    00255
    00256    cur = ftell(fs->f);
    00257    fseek(fs->f, 0, SEEK_END);
    00258    max = ftell(fs->f);
    00259
    00260    switch (whence) {
    00261    case SEEK_SET:
    00262       offset = sample_offset;
    00263       break;
    00264    case SEEK_END:
    00265       offset = max - sample_offset;
    00266       break;
    00267    case SEEK_CUR:
    00268    case SEEK_FORCECUR:
    00269       offset = cur + sample_offset;
    00270       break;
    00271    }
    00272
    00273    switch (whence) {
    00274    case SEEK_FORCECUR:
    00275       if (offset > max) {
    00276          size_t left = offset - max;
    00277          size_t res;
    00278
    00279          while (left) {
    00280             res = fwrite(alaw_silence, sizeof(alaw_silence[0]),
    00281                     (left > BUF_SIZE) ? BUF_SIZE : left, fs->f);
    00282             if (res == -1)
    00283                return res;
    00284             left -= res * sizeof(alaw_silence[0]);
    00285          }
    00286          return offset;
    00287       }
    00288       /* fall through */
    00289    default:
    00290       offset = (offset > max) ? max : offset;
    00291       offset = (offset < 0) ? 0 : offset;
    00292       return fseek(fs->f, offset, SEEK_SET);
    00293    }
    00294 }
    00295
    00296 static int pcm_trunc(struct ast_filestream *fs)
    00297 {
    00298    return ftruncate(fileno(fs->f), ftell(fs->f));
    00299 }
    00300
    00301 static long pcm_tell(struct ast_filestream *fs)
    00302 {
    00303    off_t offset;
    00304    offset = ftell(fs->f);
    00305    return offset;
    00306 }
    00307
    00308
    00309 static char *pcm_getcomment(struct ast_filestream *s)
    00310 {
    00311    return NULL;
    00312 }
    00313
    00314 int load_module()
    00315 {
    00316    int index;
    00317
    00318    for (index = 0; index < (sizeof(alaw_silence) / sizeof(alaw_silence[0])); index++)
    00319       alaw_silence[index] = AST_LIN2A(0);
    00320
    00321    return ast_format_register(name, exts, AST_FORMAT_ALAW,
    00322                pcm_open,
    00323                pcm_rewrite,
    00324                pcm_write,
    00325                pcm_seek,
    00326                pcm_trunc,
    00327                pcm_tell,
    00328                pcm_read,
    00329                pcm_close,
    00330                pcm_getcomment);
    00331 }
    00332
    00333 int unload_module()
    00334 {
    00335    return ast_format_unregister(name);
    00336 }
    00337
    00338 int usecount()
    00339 {
    00340    return glistcnt;
    00341 }
    00342
    00343 char *description()
    00344 {
    00345    return desc;
    00346 }
    00347
    00348
    00349 char *key()
    00350 {
    00351    return ASTERISK_GPL_KEY;
    00352 }