git.sesse.net Git - nageru/blob - nageru/video_encoder.cpp

   1 #include "video_encoder.h"
   2
   3 #include <assert.h>
   4 #include <stdio.h>
   5 #include <time.h>
   6 #include <unistd.h>
   7 #include <sys/types.h>
   8 #include <sys/socket.h>
   9 #include <netdb.h>
  10 #include <string>
  11 #include <thread>
  12 #include <chrono>
  13
  14 extern "C" {
  15 #include <libavutil/mem.h>
  16 }
  17
  18 #include "audio_encoder.h"
  19 #ifdef HAVE_AV1
  20 #include "av1_encoder.h"
  21 #endif
  22 #include "defs.h"
  23 #include "shared/ffmpeg_raii.h"
  24 #include "flags.h"
  25 #include "shared/httpd.h"
  26 #include "shared/mux.h"
  27 #include "quicksync_encoder.h"
  28 #include "shared/timebase.h"
  29 #include "x264_encoder.h"
  30
  31 class RefCountedFrame;
  32
  33 using namespace std;
  34 using namespace std::chrono;
  35 using namespace movit;
  36
  37 namespace {
  38
  39 string generate_local_dump_filename(int frame)
  40 {
  41         time_t now = time(NULL);
  42         tm now_tm;
  43         localtime_r(&now, &now_tm);
  44
  45         char timestamp[64];
  46         strftime(timestamp, sizeof(timestamp), "%F-%H%M%S%z", &now_tm);
  47
  48         // Use the frame number to disambiguate between two cuts starting
  49         // on the same second.
  50         char filename[256];
  51         snprintf(filename, sizeof(filename), "%s/%s%s-f%02d%s",
  52                 global_flags.recording_dir.c_str(),
  53                 LOCAL_DUMP_PREFIX, timestamp, frame % 100, LOCAL_DUMP_SUFFIX);
  54         return filename;
  55 }
  56
  57 }  // namespace
  58
  59 VideoEncoder::VideoEncoder(ResourcePool *resource_pool, QSurface *surface, const std::string &va_display, int width, int height, HTTPD *httpd, DiskSpaceEstimator *disk_space_estimator)
  60         : resource_pool(resource_pool), surface(surface), va_display(va_display), width(width), height(height), httpd(httpd), disk_space_estimator(disk_space_estimator)
  61 {
  62         // TODO: If we're outputting AV1, we can't use MPEG-TS currently.
  63         srt_oformat = av_guess_format("mpegts", nullptr, nullptr);
  64         assert(srt_oformat != nullptr);
  65
  66         oformat = av_guess_format(global_flags.stream_mux_name.c_str(), nullptr, nullptr);
  67         assert(oformat != nullptr);
  68         if (global_flags.stream_audio_codec_name.empty()) {
  69                 stream_audio_encoder.reset(new AudioEncoder(AUDIO_OUTPUT_CODEC_NAME, DEFAULT_AUDIO_OUTPUT_BIT_RATE, oformat));
  70         } else {
  71                 stream_audio_encoder.reset(new AudioEncoder(global_flags.stream_audio_codec_name, global_flags.stream_audio_codec_bitrate, oformat));
  72         }
  73         if (global_flags.x264_video_to_http || global_flags.x264_video_to_disk) {
  74                 x264_encoder.reset(new X264Encoder(oformat, /*use_separate_disk_params=*/false));
  75         }
  76         VideoCodecInterface *http_encoder = x264_encoder.get();
  77         VideoCodecInterface *disk_encoder = x264_encoder.get();
  78 #ifdef HAVE_AV1
  79         if (global_flags.av1_video_to_http) {
  80                 av1_encoder.reset(new AV1Encoder(oformat));
  81                 http_encoder = av1_encoder.get();
  82         }
  83 #endif
  84         if (global_flags.x264_separate_disk_encode) {
  85                 x264_disk_encoder.reset(new X264Encoder(oformat, /*use_separate_disk_params=*/true));
  86                 disk_encoder = x264_disk_encoder.get();
  87         }
  88
  89         string filename = generate_local_dump_filename(/*frame=*/0);
  90         quicksync_encoder.reset(new QuickSyncEncoder(filename, resource_pool, surface, va_display, width, height, oformat, http_encoder, disk_encoder, disk_space_estimator));
  91
  92         open_output_streams();
  93         stream_audio_encoder->add_mux(http_mux.get());
  94         if (srt_mux != nullptr) {
  95                 stream_audio_encoder->add_mux(srt_mux.get());
  96         }
  97         quicksync_encoder->set_http_mux(http_mux.get());
  98         if (srt_mux != nullptr) {
  99                 quicksync_encoder->set_srt_mux(srt_mux.get());
 100         }
 101         if (global_flags.x264_video_to_http) {
 102                 x264_encoder->add_mux(http_mux.get());
 103                 if (srt_mux != nullptr) {
 104                         x264_encoder->add_mux(srt_mux.get());
 105                 }
 106         }
 107 #ifdef HAVE_AV1
 108         if (global_flags.av1_video_to_http) {
 109                 av1_encoder->add_mux(http_mux.get());
 110                 if (srt_mux != nullptr) {
 111                         av1_encoder->add_mux(srt_mux.get());
 112                 }
 113         }
 114 #endif
 115 }
 116
 117 VideoEncoder::~VideoEncoder()
 118 {
 119         should_quit = true;
 120         quicksync_encoder->shutdown();
 121         x264_encoder.reset(nullptr);
 122         x264_disk_encoder.reset(nullptr);
 123         quicksync_encoder->close_file();
 124         quicksync_encoder.reset(nullptr);
 125         while (quicksync_encoders_in_shutdown.load() > 0) {
 126                 usleep(10000);
 127         }
 128 }
 129
 130 void VideoEncoder::do_cut(int frame)
 131 {
 132         string filename = generate_local_dump_filename(frame);
 133         printf("Starting new recording: %s\n", filename.c_str());
 134
 135         // Do the shutdown of the old encoder in a separate thread, since it can
 136         // take some time (it needs to wait for all the frames in the queue to be
 137         // done encoding, for one) and we are running on the main mixer thread.
 138         // However, since this means both encoders could be sending packets at
 139         // the same time, it means pts could come out of order to the stream mux,
 140         // and we need to plug it until the shutdown is complete.
 141         http_mux->plug();
 142         lock(qs_mu, qs_audio_mu);
 143         lock_guard<mutex> lock1(qs_mu, adopt_lock), lock2(qs_audio_mu, adopt_lock);
 144         QuickSyncEncoder *old_encoder = quicksync_encoder.release();  // When we go C++14, we can use move capture instead.
 145         X264Encoder *old_x264_encoder = nullptr;
 146         X264Encoder *old_x264_disk_encoder = nullptr;
 147         if (global_flags.x264_video_to_disk) {
 148                 old_x264_encoder = x264_encoder.release();
 149         }
 150         if (global_flags.x264_separate_disk_encode) {
 151                 old_x264_disk_encoder = x264_disk_encoder.release();
 152         }
 153         thread([old_encoder, old_x264_encoder, old_x264_disk_encoder, this]{
 154                 old_encoder->shutdown();
 155                 delete old_x264_encoder;
 156                 delete old_x264_disk_encoder;
 157                 old_encoder->close_file();
 158                 http_mux->unplug();
 159
 160                 // We cannot delete the encoder here, as this thread has no OpenGL context.
 161                 // We'll deal with it in begin_frame().
 162                 lock_guard<mutex> lock(qs_mu);
 163                 qs_needing_cleanup.emplace_back(old_encoder);
 164         }).detach();
 165
 166         if (global_flags.x264_video_to_disk) {
 167                 x264_encoder.reset(new X264Encoder(oformat, /*use_separate_disk_params=*/false));
 168                 assert(global_flags.x264_video_to_http);
 169                 if (global_flags.x264_video_to_http) {
 170                         x264_encoder->add_mux(http_mux.get());
 171                 }
 172                 if (overriding_bitrate != 0) {
 173                         x264_encoder->change_bitrate(overriding_bitrate);
 174                 }
 175         }
 176         X264Encoder *http_encoder = x264_encoder.get();
 177         X264Encoder *disk_encoder = x264_encoder.get();
 178         if (global_flags.x264_separate_disk_encode) {
 179                 x264_disk_encoder.reset(new X264Encoder(oformat, /*use_separate_disk_params=*/true));
 180                 disk_encoder = x264_disk_encoder.get();
 181         }
 182
 183         quicksync_encoder.reset(new QuickSyncEncoder(filename, resource_pool, surface, va_display, width, height, oformat, http_encoder, disk_encoder, disk_space_estimator));
 184         quicksync_encoder->set_http_mux(http_mux.get());
 185 }
 186
 187 void VideoEncoder::change_x264_bitrate(unsigned rate_kbit)
 188 {
 189         overriding_bitrate = rate_kbit;
 190         x264_encoder->change_bitrate(rate_kbit);
 191 }
 192
 193 void VideoEncoder::add_audio(int64_t pts, std::vector<float> audio)
 194 {
 195         // Take only qs_audio_mu, since add_audio() is thread safe
 196         // (we can only conflict with do_cut(), which takes qs_audio_mu)
 197         // and we don't want to contend with begin_frame().
 198         {
 199                 lock_guard<mutex> lock(qs_audio_mu);
 200                 quicksync_encoder->add_audio(pts, audio);
 201         }
 202         stream_audio_encoder->encode_audio(audio, pts + quicksync_encoder->global_delay());
 203 }
 204
 205 bool VideoEncoder::is_zerocopy() const
 206 {
 207         // Explicitly do _not_ take qs_mu; this is called from the mixer,
 208         // and qs_mu might be contended. is_zerocopy() is thread safe
 209         // and never called in parallel with do_cut() (both happen only
 210         // from the mixer thread).
 211         return quicksync_encoder->is_zerocopy();
 212 }
 213
 214 bool VideoEncoder::begin_frame(int64_t pts, int64_t duration, movit::YCbCrLumaCoefficients ycbcr_coefficients, const std::vector<RefCountedFrame> &input_frames, GLuint *y_tex, GLuint *cbcr_tex)
 215 {
 216         lock_guard<mutex> lock(qs_mu);
 217         qs_needing_cleanup.clear();  // Since we have an OpenGL context here, and are called regularly.
 218         return quicksync_encoder->begin_frame(pts, duration, ycbcr_coefficients, input_frames, y_tex, cbcr_tex);
 219 }
 220
 221 RefCountedGLsync VideoEncoder::end_frame()
 222 {
 223         want_srt_metric_update = true;
 224         lock_guard<mutex> lock(qs_mu);
 225         return quicksync_encoder->end_frame();
 226 }
 227
 228 void VideoEncoder::open_output_streams()
 229 {
 230         for (bool is_srt : {false, true}) {
 231                 if (is_srt && global_flags.srt_destination_host.empty()) {
 232                         continue;
 233                 }
 234
 235                 AVFormatContext *avctx = avformat_alloc_context();
 236                 avctx->oformat = is_srt ? srt_oformat : oformat;
 237
 238                 uint8_t *buf = (uint8_t *)av_malloc(MUX_BUFFER_SIZE);
 239                 avctx->pb = avio_alloc_context(buf, MUX_BUFFER_SIZE, 1, this, nullptr, nullptr, nullptr);
 240                 if (is_srt) {
 241                         avctx->pb->write_packet = &VideoEncoder::write_srt_packet_thunk;
 242                 } else {
 243                         avctx->pb->write_data_type = &VideoEncoder::write_packet2_thunk;
 244                         avctx->pb->ignore_boundary_point = 1;
 245                 }
 246
 247                 Mux::Codec video_codec;
 248                 if (global_flags.av1_video_to_http) {
 249                         video_codec = Mux::CODEC_AV1;
 250                 } else {
 251                         video_codec = Mux::CODEC_H264;
 252                 }
 253
 254                 avctx->flags = AVFMT_FLAG_CUSTOM_IO;
 255
 256                 string video_extradata;
 257                 if (global_flags.x264_video_to_http) {
 258                         video_extradata = x264_encoder->get_global_headers();
 259 #ifdef HAVE_AV1
 260                 } else if (global_flags.av1_video_to_http) {
 261                         video_extradata = av1_encoder->get_global_headers();
 262 #endif
 263                 }
 264
 265                 Mux *mux = new Mux(avctx, width, height, video_codec, video_extradata, stream_audio_encoder->get_codec_parameters().get(),
 266                         get_color_space(global_flags.ycbcr_rec709_coefficients), COARSE_TIMEBASE,
 267                         /*write_callback=*/nullptr, is_srt ? Mux::WRITE_BACKGROUND : Mux::WRITE_FOREGROUND, { is_srt ? &srt_mux_metrics : &http_mux_metrics });
 268                 if (is_srt) {
 269                         srt_mux.reset(mux);
 270                         srt_mux_metrics.init({{ "destination", "srt" }});
 271                         srt_metrics.init({{ "cardtype", "output" }});
 272                         global_metrics.add("srt_num_connection_attempts", {{ "cardtype", "output" }}, &metric_srt_num_connection_attempts);
 273                 } else {
 274                         http_mux.reset(mux);
 275                         http_mux_metrics.init({{ "destination", "http" }});
 276                 }
 277         }
 278 }
 279
 280 int VideoEncoder::write_packet2_thunk(void *opaque, uint8_t *buf, int buf_size, AVIODataMarkerType type, int64_t time)
 281 {
 282         VideoEncoder *video_encoder = (VideoEncoder *)opaque;
 283         return video_encoder->write_packet2(buf, buf_size, type, time);
 284 }
 285
 286 int VideoEncoder::write_packet2(uint8_t *buf, int buf_size, AVIODataMarkerType type, int64_t time)
 287 {
 288         if (type == AVIO_DATA_MARKER_SYNC_POINT || type == AVIO_DATA_MARKER_BOUNDARY_POINT) {
 289                 seen_sync_markers = true;
 290         } else if (type == AVIO_DATA_MARKER_UNKNOWN && !seen_sync_markers) {
 291                 // We don't know if this is a keyframe or not (the muxer could
 292                 // avoid marking it), so we just have to make the best of it.
 293                 type = AVIO_DATA_MARKER_SYNC_POINT;
 294         }
 295
 296         if (type == AVIO_DATA_MARKER_HEADER) {
 297                 http_mux_header.append((char *)buf, buf_size);
 298                 httpd->set_header(HTTPD::StreamID{ HTTPD::MAIN_STREAM, 0 }, http_mux_header);
 299         } else {
 300                 httpd->add_data(HTTPD::StreamID{ HTTPD::MAIN_STREAM, 0 }, (char *)buf, buf_size, type == AVIO_DATA_MARKER_SYNC_POINT, time, AVRational{ AV_TIME_BASE, 1 });
 301         }
 302         return buf_size;
 303 }
 304
 305 int VideoEncoder::write_srt_packet_thunk(void *opaque, uint8_t *buf, int buf_size)
 306 {
 307         VideoEncoder *video_encoder = (VideoEncoder *)opaque;
 308         return video_encoder->write_srt_packet(buf, buf_size);
 309 }
 310
 311 static string print_addrinfo(const addrinfo *ai)
 312 {
 313         char hoststr[NI_MAXHOST], portstr[NI_MAXSERV];
 314         if (getnameinfo(ai->ai_addr, ai->ai_addrlen, hoststr, sizeof(hoststr), portstr, sizeof(portstr), NI_DGRAM | NI_NUMERICHOST | NI_NUMERICSERV) != 0) {
 315                 return "<unknown address>";  // Should basically never happen, since we're not doing DNS lookups.
 316         }
 317
 318         if (ai->ai_family == AF_INET6) {
 319                 return string("[") + hoststr + "]:" + portstr;
 320         } else {
 321                 return string(hoststr) + ":" + portstr;
 322         }
 323 }
 324
 325 int VideoEncoder::open_srt_socket()
 326 {
 327         int sock = srt_create_socket();
 328         if (sock == -1) {
 329                 fprintf(stderr, "srt_create_socket(): %s\n", srt_getlasterror_str());
 330                 return -1;
 331         }
 332
 333         SRT_TRANSTYPE live = SRTT_LIVE;
 334         if (srt_setsockopt(sock, 0, SRTO_TRANSTYPE, &live, sizeof(live)) < 0) {
 335                 fprintf(stderr, "srt_setsockopt(SRTO_TRANSTYPE): %s\n", srt_getlasterror_str());
 336                 srt_close(sock);
 337                 return -1;
 338         }
 339
 340         if (srt_setsockopt(sock, 0, SRTO_LATENCY, &global_flags.srt_output_latency_ms, sizeof(global_flags.srt_output_latency_ms)) < 0) {
 341                 fprintf(stderr, "srt_setsockopt(SRTO_LATENCY): %s\n", srt_getlasterror_str());
 342                 srt_close(sock);
 343                 return -1;
 344         }
 345
 346         if (!global_flags.srt_streamid.empty()) {
 347                 if (srt_setsockopt(sock, 0, SRTO_STREAMID, global_flags.srt_streamid.data(), global_flags.srt_streamid.size()) < 0) {
 348                         fprintf(stderr, "srt_setsockopt(SRTO_STREAMID): %s\n", srt_getlasterror_str());
 349                         srt_close(sock);
 350                         return -1;
 351                 }
 352         }
 353
 354         if (!global_flags.srt_passphrase.empty()) {
 355                 if (srt_setsockopt(sock, 0, SRTO_PASSPHRASE, global_flags.srt_passphrase.data(), global_flags.srt_passphrase.size()) < 0) {
 356                         fprintf(stderr, "srt_setsockopt(SRTO_PASSPHRASE): %s\n", srt_getlasterror_str());
 357                         srt_close(sock);
 358                         return -1;
 359                 }
 360         }
 361
 362         return sock;
 363 }
 364
 365 int VideoEncoder::connect_to_srt()
 366 {
 367         // We need to specify SOCK_DGRAM as a hint, or we'll get all addresses
 368         // three times (for each of TCP, UDP, raw).
 369         addrinfo hints;
 370         memset(&hints, 0, sizeof(hints));
 371         hints.ai_flags = AI_ADDRCONFIG;
 372         hints.ai_socktype = SOCK_DGRAM;
 373
 374         addrinfo *ai;
 375         int ret = getaddrinfo(global_flags.srt_destination_host.c_str(), global_flags.srt_destination_port.c_str(), &hints, &ai);
 376         if (ret != 0) {
 377                 fprintf(stderr, "getaddrinfo(%s:%s): %s\n", global_flags.srt_destination_host.c_str(), global_flags.srt_destination_port.c_str(), gai_strerror(ret));
 378                 return -1;
 379         }
 380
 381         unique_ptr<addrinfo, decltype(freeaddrinfo) *> ai_cleanup(ai, &freeaddrinfo);
 382
 383         for (const addrinfo *cur = ai; cur != nullptr; cur = cur->ai_next) {
 384                 // Seemingly, srt_create_socket() isn't universal; once we try to connect,
 385                 // it gets locked to either IPv4 or IPv6. So we need to create a new one
 386                 // for every address we try.
 387                 int sock = open_srt_socket();
 388                 if (sock == -1) {
 389                         // Die immediately.
 390                         return sock;
 391                 }
 392                 ++metric_srt_num_connection_attempts;
 393
 394                 // We do a non-blocking connect, so that we can check should_quit
 395                 // every now and then.
 396                 int blocking = 0;
 397                 if (srt_setsockopt(sock, 0, SRTO_RCVSYN, &blocking, sizeof(blocking)) < 0) {
 398                         fprintf(stderr, "srt_setsockopt(SRTO_SNDSYN=0): %s\n", srt_getlasterror_str());
 399                         srt_close(sock);
 400                         continue;
 401                 }
 402                 if (srt_connect(sock, cur->ai_addr, cur->ai_addrlen) < 0) {
 403                         fprintf(stderr, "srt_connect(%s): %s\n", print_addrinfo(cur).c_str(), srt_getlasterror_str());
 404                         srt_close(sock);
 405                         continue;
 406                 }
 407                 int eid = srt_epoll_create();
 408                 if (eid < 0) {
 409                         fprintf(stderr, "srt_epoll_create(): %s\n", srt_getlasterror_str());
 410                         srt_close(sock);
 411                         continue;
 412                 }
 413                 int modes = SRT_EPOLL_ERR | SRT_EPOLL_OUT;
 414                 if (srt_epoll_add_usock(eid, sock, &modes) < 0) {
 415                         fprintf(stderr, "srt_epoll_usock(): %s\n", srt_getlasterror_str());
 416                         srt_close(sock);
 417                         srt_epoll_release(eid);
 418                         continue;
 419                 }
 420                 bool ok;
 421                 while (!should_quit.load()) {
 422                         SRTSOCKET errfds[1], writefds[1];
 423                         int num_errfds = 1, num_writefds = 1;
 424                         int poll_time_ms = 100;
 425                         int ret = srt_epoll_wait(eid, errfds, &num_errfds, writefds, &num_writefds, poll_time_ms, 0, 0, 0, 0);
 426                         if (ret < 0) {
 427                                 if (srt_getlasterror(nullptr) == SRT_ETIMEOUT) {
 428                                         continue;
 429                                 } else {
 430                                         fprintf(stderr, "srt_epoll_wait(): %s\n", srt_getlasterror_str());
 431                                         srt_close(sock);
 432                                         srt_epoll_release(eid);
 433                                         return -1;
 434                                 }
 435                         } else if (ret > 0) {
 436                                 // The SRT epoll framework is pretty odd, but seemingly,
 437                                 // this is the way. Getting the same error code as srt_connect()
 438                                 // would normally return seems to be impossible, though.
 439                                 ok = (num_errfds == 0);
 440                                 break;
 441                                 fprintf(stderr, "num_errfds=%d num_writefds=%d last_err=%s\n", num_errfds, num_writefds, srt_getlasterror_str());
 442                                 break;
 443                         }
 444                 }
 445                 srt_epoll_release(eid);
 446                 if (should_quit.load()) {
 447                         srt_close(sock);
 448                         return -1;
 449                 }
 450                 if (ok) {
 451                         fprintf(stderr, "Connected to destination SRT endpoint at %s.\n", print_addrinfo(cur).c_str());
 452                         return sock;
 453                 } else {
 454                         fprintf(stderr, "srt_connect(%s): %s\n", print_addrinfo(cur).c_str(), srt_getlasterror_str());
 455                         srt_close(sock);
 456                 }
 457         }
 458
 459         // Out of candidates, so give up.
 460         return -1;
 461 }
 462
 463 int VideoEncoder::write_srt_packet(uint8_t *buf, int buf_size)
 464 {
 465         if (want_srt_metric_update.exchange(false) && srt_sock != -1) {
 466                 srt_metrics.update_srt_stats(srt_sock);
 467         }
 468
 469         bool has_drained = false;
 470         bool trying_reconnect = false;
 471         steady_clock::time_point first_connect_start;
 472
 473         while (buf_size > 0 && !should_quit.load()) {
 474                 if (srt_sock == -1) {
 475                         if (!trying_reconnect) {
 476                                 first_connect_start = steady_clock::now();
 477                                 trying_reconnect = true;
 478                         }
 479                         srt_sock = connect_to_srt();
 480                         if (srt_sock == -1) {
 481                                 usleep(100000);
 482                                 if (!has_drained && duration<double>(steady_clock::now() - first_connect_start).count() >= global_flags.srt_output_latency_ms * 1e-3) {
 483                                         // The entire concept for SRT is to have fixed, low latency.
 484                                         // If we've been out for more than a latency period, we shouldn't
 485                                         // try to send the entire backlog. (But we should be tolerant
 486                                         // of a quick disconnect and reconnect.) Maybe it would be better
 487                                         // to have a sliding window of how much we remove, but it quickly
 488                                         // starts getting esoteric, so juts drop it all.
 489                                         fprintf(stderr, "WARNING: No SRT connection for more than %d ms, dropping data.\n",
 490                                                 global_flags.srt_output_latency_ms);
 491                                         srt_mux->drain();
 492                                         has_drained = true;
 493                                 }
 494                                 continue;
 495                         }
 496                         srt_metrics.update_srt_stats(srt_sock);
 497                 }
 498                 if (has_drained) {
 499                         // Now that we're reconnected, we can start accepting data again,
 500                         // but discard the rest of this write (it is very old by now).
 501                         srt_mux->undrain();
 502                         break;
 503                 }
 504                 int to_send = min(buf_size, SRT_LIVE_DEF_PLSIZE);
 505                 int ret = srt_send(srt_sock, (char *)buf, to_send);
 506                 if (ret < 0)  {
 507                         fprintf(stderr, "srt_send(): %s\n", srt_getlasterror_str());
 508                         srt_close(srt_sock);
 509                         srt_metrics.metric_srt_uptime_seconds = 0.0 / 0.0;
 510                         if (!trying_reconnect) {
 511                                 first_connect_start = steady_clock::now();
 512                                 trying_reconnect = true;
 513                         }
 514                         srt_sock = connect_to_srt();
 515                         continue;
 516                 }
 517                 buf += ret;
 518                 buf_size -= ret;
 519         }
 520         return buf_size;
 521 }
 522