stream/cache2.c

   1 /*
   2  * This file is part of MPlayer.
   3  *
   4  * MPlayer is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * MPlayer is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with MPlayer; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #include "config.h"
  20
  21 // Initial draft of my new cache system...
  22 // Note it runs in 2 processes (using fork()), but doesn't require locking!!
  23 // TODO: seeking, data consistency checking
  24
  25 #define READ_SLEEP_TIME 10
  26 // These defines are used to reduce the cost of many successive
  27 // seeks (e.g. when a file has no index) by spinning quickly at first.
  28 #define INITIAL_FILL_USLEEP_TIME 1000
  29 #define INITIAL_FILL_USLEEP_COUNT 10
  30 #define FILL_USLEEP_TIME 50000
  31 #define PREFILL_SLEEP_TIME 200
  32 #define CONTROL_SLEEP_TIME 0
  33
  34 #include <stdio.h>
  35 #include <stdlib.h>
  36 #include <string.h>
  37 #include <signal.h>
  38 #include <sys/types.h>
  39 #include <unistd.h>
  40 #include <errno.h>
  41
  42 #include "libavutil/avutil.h"
  43 #include "osdep/shmem.h"
  44 #include "osdep/timer.h"
  45 #if defined(__MINGW32__)
  46 #include <windows.h>
  47 static void ThreadProc( void *s );
  48 #elif defined(__OS2__)
  49 #define INCL_DOS
  50 #include <os2.h>
  51 static void ThreadProc( void *s );
  52 #elif defined(PTHREAD_CACHE)
  53 #include <pthread.h>
  54 static void *ThreadProc(void *s);
  55 #else
  56 #include <sys/wait.h>
  57 #define FORKED_CACHE 1
  58 #endif
  59 #ifndef FORKED_CACHE
  60 #define FORKED_CACHE 0
  61 #endif
  62
  63 #include "mp_msg.h"
  64
  65 #include "stream.h"
  66 #include "cache2.h"
  67
  68 typedef struct {
  69   // constats:
  70   unsigned char *buffer;      // base pointer of the allocated buffer memory
  71   int buffer_size; // size of the allocated buffer memory
  72   int sector_size; // size of a single sector (2048/2324)
  73   int back_size;   // we should keep back_size amount of old bytes for backward seek
  74   int fill_limit;  // we should fill buffer only if space>=fill_limit
  75   int seek_limit;  // keep filling cache if distance is less that seek limit
  76   // filler's pointers:
  77   int eof;
  78   off_t min_filepos; // buffer contain only a part of the file, from min-max pos
  79   off_t max_filepos;
  80   off_t offset;      // filepos <-> bufferpos  offset value (filepos of the buffer's first byte)
  81   // reader's pointers:
  82   off_t read_filepos;
  83   // commands/locking:
  84 //  int seek_lock;   // 1 if we will seek/reset buffer, 2 if we are ready for cmd
  85 //  int fifo_flag;  // 1 if we should use FIFO to notice cache about buffer reads.
  86   // callback
  87   stream_t* stream;
  88   volatile int control;
  89   volatile unsigned control_uint_arg;
  90   volatile double control_double_arg;
  91   volatile int control_res;
  92   volatile off_t control_new_pos;
  93   volatile double stream_time_length;
  94 } cache_vars_t;
  95
  96 static int min_fill=0;
  97
  98 static void cache_wakeup(stream_t *s)
  99 {
 100 #if FORKED_CACHE
 101   // signal process to wake up immediately
 102   kill(s->cache_pid, SIGUSR1);
 103 #endif
 104 }
 105
 106 static int cache_read(cache_vars_t *s, unsigned char *buf, int size)
 107 {
 108   int total=0;
 109   int sleep_count = 0;
 110   int last_max = s->max_filepos;
 111   while(size>0){
 112     int pos,newb,len;
 113
 114   //printf("CACHE2_READ: 0x%X <= 0x%X <= 0x%X  \n",s->min_filepos,s->read_filepos,s->max_filepos);
 115
 116     if(s->read_filepos>=s->max_filepos || s->read_filepos<s->min_filepos){
 117         // eof?
 118         if(s->eof) break;
 119         if (s->max_filepos == last_max) {
 120             if (sleep_count++ == 10)
 121                 mp_msg(MSGT_CACHE, MSGL_WARN, "Cache not filling, consider increasing -cache and/or -cache-min!\n");
 122         } else {
 123             last_max = s->max_filepos;
 124             sleep_count = 0;
 125         }
 126         // waiting for buffer fill...
 127         if (stream_check_interrupt(READ_SLEEP_TIME)) {
 128             s->eof = 1;
 129             break;
 130         }
 131         continue; // try again...
 132     }
 133     sleep_count = 0;
 134
 135     newb=s->max_filepos-s->read_filepos; // new bytes in the buffer
 136     if(newb<min_fill) min_fill=newb; // statistics...
 137
 138 //    printf("*** newb: %d bytes ***\n",newb);
 139
 140     pos=s->read_filepos - s->offset;
 141     if(pos<0) pos+=s->buffer_size; else
 142     if(pos>=s->buffer_size) pos-=s->buffer_size;
 143
 144     if(newb>s->buffer_size-pos) newb=s->buffer_size-pos; // handle wrap...
 145     if(newb>size) newb=size;
 146
 147     // check:
 148     if(s->read_filepos<s->min_filepos) mp_msg(MSGT_CACHE,MSGL_ERR,"Ehh. s->read_filepos<s->min_filepos !!! Report bug...\n");
 149
 150     // len=write(mem,newb)
 151     //printf("Buffer read: %d bytes\n",newb);
 152     memcpy(buf,&s->buffer[pos],newb);
 153     buf+=newb;
 154     len=newb;
 155     // ...
 156
 157     s->read_filepos+=len;
 158     size-=len;
 159     total+=len;
 160
 161   }
 162   return total;
 163 }
 164
 165 static int cache_fill(cache_vars_t *s)
 166 {
 167   int back,back2,newb,space,len,pos;
 168   off_t read=s->read_filepos;
 169   int read_chunk;
 170   int wraparound_copy = 0;
 171
 172   if(read<s->min_filepos || read>s->max_filepos){
 173       // seek...
 174       mp_msg(MSGT_CACHE,MSGL_DBG2,"Out of boundaries... seeking to 0x%"PRIX64"  \n",(int64_t)read);
 175       // drop cache contents only if seeking backward or too much fwd.
 176       // This is also done for on-disk files, since it loses the backseek cache.
 177       // That in turn can cause major bandwidth increase and performance
 178       // issues with e.g. mov or badly interleaved files
 179       if(read<s->min_filepos || read>=s->max_filepos+s->seek_limit)
 180       {
 181         s->offset= // FIXME!?
 182         s->min_filepos=s->max_filepos=read; // drop cache content :(
 183         if(s->stream->eof) stream_reset(s->stream);
 184         stream_seek_internal(s->stream,read);
 185         mp_msg(MSGT_CACHE,MSGL_DBG2,"Seek done. new pos: 0x%"PRIX64"  \n",(int64_t)stream_tell(s->stream));
 186       }
 187   }
 188
 189   // calc number of back-bytes:
 190   back=read - s->min_filepos;
 191   if(back<0) back=0; // strange...
 192   if(back>s->back_size) back=s->back_size;
 193
 194   // calc number of new bytes:
 195   newb=s->max_filepos - read;
 196   if(newb<0) newb=0; // strange...
 197
 198   // calc free buffer space:
 199   space=s->buffer_size - (newb+back);
 200
 201   // calc bufferpos:
 202   pos=s->max_filepos - s->offset;
 203   if(pos>=s->buffer_size) pos-=s->buffer_size; // wrap-around
 204
 205   if(space<s->fill_limit){
 206 //    printf("Buffer is full (%d bytes free, limit: %d)\n",space,s->fill_limit);
 207     return 0; // no fill...
 208   }
 209
 210 //  printf("### read=0x%X  back=%d  newb=%d  space=%d  pos=%d\n",read,back,newb,space,pos);
 211
 212   // try to avoid wrap-around. If not possible due to sector size
 213   // do an extra copy.
 214   if(space>s->buffer_size-pos) {
 215     if (s->buffer_size-pos >= s->sector_size) {
 216       space=s->buffer_size-pos;
 217     } else {
 218       space = s->sector_size;
 219       wraparound_copy = 1;
 220     }
 221   }
 222
 223   // limit one-time block size
 224   read_chunk = s->stream->read_chunk;
 225   if (!read_chunk) read_chunk = 4*s->sector_size;
 226   space = FFMIN(space, read_chunk);
 227
 228 #if 1
 229   // back+newb+space <= buffer_size
 230   back2=s->buffer_size-(space+newb); // max back size
 231   if(s->min_filepos<(read-back2)) s->min_filepos=read-back2;
 232 #else
 233   s->min_filepos=read-back; // avoid seeking-back to temp area...
 234 #endif
 235
 236   if (wraparound_copy) {
 237     int to_copy;
 238     len = stream_read_internal(s->stream, s->stream->buffer, space);
 239     to_copy = FFMIN(len, s->buffer_size-pos);
 240     memcpy(s->buffer + pos, s->stream->buffer, to_copy);
 241     memcpy(s->buffer, s->stream->buffer + to_copy, len - to_copy);
 242   } else
 243   len = stream_read_internal(s->stream, &s->buffer[pos], space);
 244   s->eof= !len;
 245
 246   s->max_filepos+=len;
 247   if(pos+len>=s->buffer_size){
 248       // wrap...
 249       s->offset+=s->buffer_size;
 250   }
 251
 252   return len;
 253
 254 }
 255
 256 static int cache_execute_control(cache_vars_t *s) {
 257   double double_res;
 258   unsigned uint_res;
 259   static unsigned last;
 260   int quit = s->control == -2;
 261   if (quit || !s->stream->control) {
 262     s->stream_time_length = 0;
 263     s->control_new_pos = 0;
 264     s->control_res = STREAM_UNSUPPORTED;
 265     s->control = -1;
 266     return !quit;
 267   }
 268   if (GetTimerMS() - last > 99) {
 269     double len;
 270     if (s->stream->control(s->stream, STREAM_CTRL_GET_TIME_LENGTH, &len) == STREAM_OK)
 271       s->stream_time_length = len;
 272     else
 273       s->stream_time_length = 0;
 274     last = GetTimerMS();
 275   }
 276   if (s->control == -1) return 1;
 277   switch (s->control) {
 278     case STREAM_CTRL_SEEK_TO_TIME:
 279       double_res = s->control_double_arg;
 280     case STREAM_CTRL_GET_CURRENT_TIME:
 281     case STREAM_CTRL_GET_ASPECT_RATIO:
 282       s->control_res = s->stream->control(s->stream, s->control, &double_res);
 283       s->control_double_arg = double_res;
 284       break;
 285     case STREAM_CTRL_SEEK_TO_CHAPTER:
 286     case STREAM_CTRL_SET_ANGLE:
 287       uint_res = s->control_uint_arg;
 288     case STREAM_CTRL_GET_NUM_CHAPTERS:
 289     case STREAM_CTRL_GET_CURRENT_CHAPTER:
 290     case STREAM_CTRL_GET_NUM_ANGLES:
 291     case STREAM_CTRL_GET_ANGLE:
 292       s->control_res = s->stream->control(s->stream, s->control, &uint_res);
 293       s->control_uint_arg = uint_res;
 294       break;
 295     default:
 296       s->control_res = STREAM_UNSUPPORTED;
 297       break;
 298   }
 299   s->control_new_pos = s->stream->pos;
 300   s->control = -1;
 301   return 1;
 302 }
 303
 304 static void *shared_alloc(int size) {
 305 #if FORKED_CACHE
 306     return shmem_alloc(size);
 307 #else
 308     return malloc(size);
 309 #endif
 310 }
 311
 312 static void shared_free(void *ptr, int size) {
 313 #if FORKED_CACHE
 314     shmem_free(ptr, size);
 315 #else
 316     free(ptr);
 317 #endif
 318 }
 319
 320 static cache_vars_t* cache_init(int size,int sector){
 321   int num;
 322   cache_vars_t* s=shared_alloc(sizeof(cache_vars_t));
 323   if(s==NULL) return NULL;
 324
 325   memset(s,0,sizeof(cache_vars_t));
 326   num=size/sector;
 327   if(num < 16){
 328      num = 16;
 329   }//32kb min_size
 330   s->buffer_size=num*sector;
 331   s->sector_size=sector;
 332   s->buffer=shared_alloc(s->buffer_size);
 333
 334   if(s->buffer == NULL){
 335     shared_free(s, sizeof(cache_vars_t));
 336     return NULL;
 337   }
 338
 339   s->fill_limit=8*sector;
 340   s->back_size=s->buffer_size/2;
 341   return s;
 342 }
 343
 344 void cache_uninit(stream_t *s) {
 345   cache_vars_t* c = s->cache_data;
 346   if(s->cache_pid) {
 347 #if !FORKED_CACHE
 348     cache_do_control(s, -2, NULL);
 349 #else
 350     kill(s->cache_pid,SIGKILL);
 351     waitpid(s->cache_pid,NULL,0);
 352 #endif
 353     s->cache_pid = 0;
 354   }
 355   if(!c) return;
 356   shared_free(c->buffer, c->buffer_size);
 357   c->buffer = NULL;
 358   c->stream = NULL;
 359   shared_free(s->cache_data, sizeof(cache_vars_t));
 360   s->cache_data = NULL;
 361 }
 362
 363 static void exit_sighandler(int x){
 364   // close stream
 365   exit(0);
 366 }
 367
 368 static void dummy_sighandler(int x) {
 369 }
 370
 371 /**
 372  * Main loop of the cache process or thread.
 373  */
 374 static void cache_mainloop(cache_vars_t *s) {
 375     int sleep_count = 0;
 376 #if FORKED_CACHE
 377     struct sigaction sa = { .sa_handler = SIG_IGN };
 378     sigaction(SIGUSR1, &sa, NULL);
 379 #endif
 380     do {
 381         if (!cache_fill(s)) {
 382 #if FORKED_CACHE
 383             // Let signal wake us up, we cannot leave this
 384             // enabled since we do not handle EINTR in most places.
 385             // This might need extra code to work on BSD.
 386             sa.sa_handler = dummy_sighandler;
 387             sigaction(SIGUSR1, &sa, NULL);
 388 #endif
 389             if (sleep_count < INITIAL_FILL_USLEEP_COUNT) {
 390                 sleep_count++;
 391                 usec_sleep(INITIAL_FILL_USLEEP_TIME);
 392             } else
 393                 usec_sleep(FILL_USLEEP_TIME); // idle
 394 #if FORKED_CACHE
 395             sa.sa_handler = SIG_IGN;
 396             sigaction(SIGUSR1, &sa, NULL);
 397 #endif
 398         } else
 399             sleep_count = 0;
 400     } while (cache_execute_control(s));
 401 }
 402
 403 /**
 404  * \return 1 on success, 0 if the function was interrupted and -1 on error
 405  */
 406 int stream_enable_cache(stream_t *stream,int size,int min,int seek_limit){
 407   int ss = stream->sector_size ? stream->sector_size : STREAM_BUFFER_SIZE;
 408   int res = -1;
 409   cache_vars_t* s;
 410
 411   if (stream->flags & STREAM_NON_CACHEABLE) {
 412     mp_msg(MSGT_CACHE,MSGL_STATUS,"\rThis stream is non-cacheable\n");
 413     return 1;
 414   }
 415
 416   s=cache_init(size,ss);
 417   if(s == NULL) return -1;
 418   stream->cache_data=s;
 419   s->stream=stream; // callback
 420   s->seek_limit=seek_limit;
 421
 422
 423   //make sure that we won't wait from cache_fill
 424   //more data than it is allowed to fill
 425   if (s->seek_limit > s->buffer_size - s->fill_limit ){
 426      s->seek_limit = s->buffer_size - s->fill_limit;
 427   }
 428   if (min > s->buffer_size - s->fill_limit) {
 429      min = s->buffer_size - s->fill_limit;
 430   }
 431   // to make sure we wait for the cache process/thread to be active
 432   // before continuing
 433   if (min <= 0)
 434     min = 1;
 435
 436 #if FORKED_CACHE
 437   if((stream->cache_pid=fork())){
 438     if ((pid_t)stream->cache_pid == -1)
 439       stream->cache_pid = 0;
 440 #else
 441   {
 442     stream_t* stream2=malloc(sizeof(stream_t));
 443     memcpy(stream2,s->stream,sizeof(stream_t));
 444     s->stream=stream2;
 445 #if defined(__MINGW32__)
 446     stream->cache_pid = _beginthread( ThreadProc, 0, s );
 447 #elif defined(__OS2__)
 448     stream->cache_pid = _beginthread( ThreadProc, NULL, 256 * 1024, s );
 449 #else
 450     {
 451     pthread_t tid;
 452     pthread_create(&tid, NULL, ThreadProc, s);
 453     stream->cache_pid = 1;
 454     }
 455 #endif
 456 #endif
 457     if (!stream->cache_pid) {
 458         mp_msg(MSGT_CACHE, MSGL_ERR,
 459                "Starting cache process/thread failed: %s.\n", strerror(errno));
 460         goto err_out;
 461     }
 462     // wait until cache is filled at least prefill_init %
 463     mp_msg(MSGT_CACHE,MSGL_V,"CACHE_PRE_INIT: %"PRId64" [%"PRId64"] %"PRId64"  pre:%d  eof:%d  \n",
 464         (int64_t)s->min_filepos,(int64_t)s->read_filepos,(int64_t)s->max_filepos,min,s->eof);
 465     while(s->read_filepos<s->min_filepos || s->max_filepos-s->read_filepos<min){
 466         mp_tmsg(MSGT_CACHE,MSGL_STATUS,"\rCache fill: %5.2f%% (%"PRId64" bytes)   ",
 467             100.0*(float)(s->max_filepos-s->read_filepos)/(float)(s->buffer_size),
 468             (int64_t)s->max_filepos-s->read_filepos
 469         );
 470         if(s->eof) break; // file is smaller than prefill size
 471         if(stream_check_interrupt(PREFILL_SLEEP_TIME)) {
 472           res = 0;
 473           goto err_out;
 474         }
 475     }
 476     mp_msg(MSGT_CACHE,MSGL_STATUS,"\n");
 477     return 1; // parent exits
 478
 479 err_out:
 480     cache_uninit(stream);
 481     return res;
 482   }
 483
 484 #if FORKED_CACHE
 485   signal(SIGTERM,exit_sighandler); // kill
 486   cache_mainloop(s);
 487   // make sure forked code never leaves this function
 488   exit(0);
 489 #endif
 490 }
 491
 492 #if !FORKED_CACHE
 493 #if defined(__MINGW32__) || defined(__OS2__)
 494 static void ThreadProc( void *s ){
 495   cache_mainloop(s);
 496   _endthread();
 497 }
 498 #else
 499 static void *ThreadProc( void *s ){
 500   cache_mainloop(s);
 501   return NULL;
 502 }
 503 #endif
 504 #endif
 505
 506 int cache_stream_fill_buffer(stream_t *s){
 507   int len;
 508   int sector_size;
 509   if(!s->cache_pid) return stream_fill_buffer(s);
 510
 511   if(s->pos!=((cache_vars_t*)s->cache_data)->read_filepos) mp_msg(MSGT_CACHE,MSGL_ERR,"!!! read_filepos differs!!! report this bug...\n");
 512   sector_size = ((cache_vars_t*)s->cache_data)->sector_size;
 513   if (sector_size > STREAM_MAX_SECTOR_SIZE) {
 514     mp_msg(MSGT_CACHE, MSGL_ERR, "Sector size %i larger than maximum %i\n", sector_size, STREAM_MAX_SECTOR_SIZE);
 515     sector_size = STREAM_MAX_SECTOR_SIZE;
 516   }
 517
 518   len=cache_read(s->cache_data,s->buffer, sector_size);
 519   //printf("cache_stream_fill_buffer->read -> %d\n",len);
 520
 521   if(len<=0){ s->eof=1; s->buf_pos=s->buf_len=0; return 0; }
 522   s->eof=0;
 523   s->buf_pos=0;
 524   s->buf_len=len;
 525   s->pos+=len;
 526 //  printf("[%d]",len);fflush(stdout);
 527   if (s->capture_file)
 528     stream_capture_do(s);
 529   return len;
 530
 531 }
 532
 533 int cache_fill_status(stream_t *s) {
 534   cache_vars_t *cv;
 535   if (!s || !s->cache_data)
 536     return -1;
 537   cv = s->cache_data;
 538   return (cv->max_filepos-cv->read_filepos)/(cv->buffer_size / 100);
 539 }
 540
 541 int cache_stream_seek_long(stream_t *stream,off_t pos){
 542   cache_vars_t* s;
 543   off_t newpos;
 544   if(!stream->cache_pid) return stream_seek_long(stream,pos);
 545
 546   s=stream->cache_data;
 547 //  s->seek_lock=1;
 548
 549   mp_msg(MSGT_CACHE,MSGL_DBG2,"CACHE2_SEEK: 0x%"PRIX64" <= 0x%"PRIX64" (0x%"PRIX64") <= 0x%"PRIX64"  \n",s->min_filepos,pos,s->read_filepos,s->max_filepos);
 550
 551   newpos=pos/s->sector_size; newpos*=s->sector_size; // align
 552   stream->pos=s->read_filepos=newpos;
 553   s->eof=0; // !!!!!!!
 554   cache_wakeup(stream);
 555
 556   cache_stream_fill_buffer(stream);
 557
 558   pos-=newpos;
 559   if(pos>=0 && pos<=stream->buf_len){
 560     stream->buf_pos=pos; // byte position in sector
 561     return 1;
 562   }
 563
 564 //  stream->buf_pos=stream->buf_len=0;
 565 //  return 1;
 566
 567   mp_msg(MSGT_CACHE,MSGL_V,"cache_stream_seek: WARNING! Can't seek to 0x%"PRIX64" !\n",(int64_t)(pos+newpos));
 568   return 0;
 569 }
 570
 571 int cache_do_control(stream_t *stream, int cmd, void *arg) {
 572   int sleep_count = 0;
 573   cache_vars_t* s = stream->cache_data;
 574   switch (cmd) {
 575     case STREAM_CTRL_SEEK_TO_TIME:
 576       s->control_double_arg = *(double *)arg;
 577       s->control = cmd;
 578       break;
 579     case STREAM_CTRL_SEEK_TO_CHAPTER:
 580     case STREAM_CTRL_SET_ANGLE:
 581       s->control_uint_arg = *(unsigned *)arg;
 582       s->control = cmd;
 583       break;
 584 // the core might call these every frame, they are too slow for this...
 585     case STREAM_CTRL_GET_TIME_LENGTH:
 586 //    case STREAM_CTRL_GET_CURRENT_TIME:
 587       *(double *)arg = s->stream_time_length;
 588       return s->stream_time_length ? STREAM_OK : STREAM_UNSUPPORTED;
 589     case STREAM_CTRL_GET_NUM_CHAPTERS:
 590     case STREAM_CTRL_GET_CURRENT_CHAPTER:
 591     case STREAM_CTRL_GET_ASPECT_RATIO:
 592     case STREAM_CTRL_GET_NUM_ANGLES:
 593     case STREAM_CTRL_GET_ANGLE:
 594     case -2:
 595       s->control = cmd;
 596       break;
 597     default:
 598       return STREAM_UNSUPPORTED;
 599   }
 600   cache_wakeup(stream);
 601   while (s->control != -1) {
 602     if (sleep_count++ == 1000)
 603       mp_msg(MSGT_CACHE, MSGL_WARN, "Cache not responding!\n");
 604     if (stream_check_interrupt(CONTROL_SLEEP_TIME)) {
 605       s->eof = 1;
 606       return STREAM_UNSUPPORTED;
 607     }
 608   }
 609   switch (cmd) {
 610     case STREAM_CTRL_GET_TIME_LENGTH:
 611     case STREAM_CTRL_GET_CURRENT_TIME:
 612     case STREAM_CTRL_GET_ASPECT_RATIO:
 613       *(double *)arg = s->control_double_arg;
 614       break;
 615     case STREAM_CTRL_GET_NUM_CHAPTERS:
 616     case STREAM_CTRL_GET_CURRENT_CHAPTER:
 617     case STREAM_CTRL_GET_NUM_ANGLES:
 618     case STREAM_CTRL_GET_ANGLE:
 619       *(unsigned *)arg = s->control_uint_arg;
 620       break;
 621     case STREAM_CTRL_SEEK_TO_CHAPTER:
 622     case STREAM_CTRL_SEEK_TO_TIME:
 623     case STREAM_CTRL_SET_ANGLE:
 624       if (s->control_res != STREAM_UNSUPPORTED)
 625           stream->pos = s->read_filepos = s->control_new_pos;
 626       break;
 627   }
 628   return s->control_res;
 629 }