WebPEncodingError VP8LEncodeStream()

in Extended/libwebp/src/enc/vp8l_enc.c [1677:1816]

• 120 lines of code
• 27 McCabe index (conditional complexity)

WebPEncodingError VP8LEncodeStream(const WebPConfig* const config,
                                   const WebPPicture* const picture,
                                   VP8LBitWriter* const bw_main,
                                   int use_cache) {
  WebPEncodingError err = VP8_ENC_OK;
  VP8LEncoder* const enc_main = VP8LEncoderNew(config, picture);
  VP8LEncoder* enc_side = NULL;
  CrunchConfig crunch_configs[CRUNCH_CONFIGS_MAX];
  int num_crunch_configs_main, num_crunch_configs_side = 0;
  int idx;
  int red_and_blue_always_zero = 0;
  WebPWorker worker_main, worker_side;
  StreamEncodeContext params_main, params_side;
  // The main thread uses picture->stats, the side thread uses stats_side.
  WebPAuxStats stats_side;
  VP8LBitWriter bw_side;
  const WebPWorkerInterface* const worker_interface = WebPGetWorkerInterface();
  int ok_main;

  // Analyze image (entropy, num_palettes etc)
  if (enc_main == NULL ||
      !EncoderAnalyze(enc_main, crunch_configs, &num_crunch_configs_main,
                      &red_and_blue_always_zero) ||
      !EncoderInit(enc_main) || !VP8LBitWriterInit(&bw_side, 0)) {
    err = VP8_ENC_ERROR_OUT_OF_MEMORY;
    goto Error;
  }

  // Split the configs between the main and side threads (if any).
  if (config->thread_level > 0) {
    num_crunch_configs_side = num_crunch_configs_main / 2;
    for (idx = 0; idx < num_crunch_configs_side; ++idx) {
      params_side.crunch_configs_[idx] =
          crunch_configs[num_crunch_configs_main - num_crunch_configs_side +
                         idx];
    }
    params_side.num_crunch_configs_ = num_crunch_configs_side;
  }
  num_crunch_configs_main -= num_crunch_configs_side;
  for (idx = 0; idx < num_crunch_configs_main; ++idx) {
    params_main.crunch_configs_[idx] = crunch_configs[idx];
  }
  params_main.num_crunch_configs_ = num_crunch_configs_main;

  // Fill in the parameters for the thread workers.
  {
    const int params_size = (num_crunch_configs_side > 0) ? 2 : 1;
    for (idx = 0; idx < params_size; ++idx) {
      // Create the parameters for each worker.
      WebPWorker* const worker = (idx == 0) ? &worker_main : &worker_side;
      StreamEncodeContext* const param =
          (idx == 0) ? &params_main : &params_side;
      param->config_ = config;
      param->picture_ = picture;
      param->use_cache_ = use_cache;
      param->red_and_blue_always_zero_ = red_and_blue_always_zero;
      if (idx == 0) {
        param->stats_ = picture->stats;
        param->bw_ = bw_main;
        param->enc_ = enc_main;
      } else {
        param->stats_ = (picture->stats == NULL) ? NULL : &stats_side;
        // Create a side bit writer.
        if (!VP8LBitWriterClone(bw_main, &bw_side)) {
          err = VP8_ENC_ERROR_OUT_OF_MEMORY;
          goto Error;
        }
        param->bw_ = &bw_side;
        // Create a side encoder.
        enc_side = VP8LEncoderNew(config, picture);
        if (enc_side == NULL || !EncoderInit(enc_side)) {
          err = VP8_ENC_ERROR_OUT_OF_MEMORY;
          goto Error;
        }
        // Copy the values that were computed for the main encoder.
        enc_side->histo_bits_ = enc_main->histo_bits_;
        enc_side->transform_bits_ = enc_main->transform_bits_;
        enc_side->palette_size_ = enc_main->palette_size_;
        memcpy(enc_side->palette_, enc_main->palette_,
               sizeof(enc_main->palette_));
        param->enc_ = enc_side;
      }
      // Create the workers.
      worker_interface->Init(worker);
      worker->data1 = param;
      worker->data2 = NULL;
      worker->hook = EncodeStreamHook;
    }
  }

  // Start the second thread if needed.
  if (num_crunch_configs_side != 0) {
    if (!worker_interface->Reset(&worker_side)) {
      err = VP8_ENC_ERROR_OUT_OF_MEMORY;
      goto Error;
    }
#if !defined(WEBP_DISABLE_STATS)
    // This line is here and not in the param initialization above to remove a
    // Clang static analyzer warning.
    if (picture->stats != NULL) {
      memcpy(&stats_side, picture->stats, sizeof(stats_side));
    }
#endif
    // This line is only useful to remove a Clang static analyzer warning.
    params_side.err_ = VP8_ENC_OK;
    worker_interface->Launch(&worker_side);
  }
  // Execute the main thread.
  worker_interface->Execute(&worker_main);
  ok_main = worker_interface->Sync(&worker_main);
  worker_interface->End(&worker_main);
  if (num_crunch_configs_side != 0) {
    // Wait for the second thread.
    const int ok_side = worker_interface->Sync(&worker_side);
    worker_interface->End(&worker_side);
    if (!ok_main || !ok_side) {
      err = ok_main ? params_side.err_ : params_main.err_;
      goto Error;
    }
    if (VP8LBitWriterNumBytes(&bw_side) < VP8LBitWriterNumBytes(bw_main)) {
      VP8LBitWriterSwap(bw_main, &bw_side);
#if !defined(WEBP_DISABLE_STATS)
      if (picture->stats != NULL) {
        memcpy(picture->stats, &stats_side, sizeof(*picture->stats));
      }
#endif
    }
  } else {
    if (!ok_main) {
      err = params_main.err_;
      goto Error;
    }
  }

Error:
  VP8LBitWriterWipeOut(&bw_side);
  VP8LEncoderDelete(enc_main);
  VP8LEncoderDelete(enc_side);
  return err;
}