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    // gst-plugin/gst-audio-source.cc
    
    // Copyright 2013  Tanel Alumae, Tallinn University of Technology
    
    // See ../../COPYING for clarification regarding multiple authors
    //
    // Licensed under the Apache License, Version 2.0 (the "License");
    // you may not use this file except in compliance with the License.
    // You may obtain a copy of the License at
    //
    //  http://www.apache.org/licenses/LICENSE-2.0
    //
    // THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    // KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
    // WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
    // MERCHANTABLITY OR NON-INFRINGEMENT.
    // See the Apache 2 License for the specific language governing permissions and
    // limitations under the License.
    
    #include <algorithm>
    
    #include "gst-audio-source.h"
    
    namespace kaldi {
    
    
    GstBufferSource::GstBufferSource() :
      ended_(false) {
      buf_queue_ = g_async_queue_new();
      current_buffer_ = NULL;
      pos_in_current_buf_ = 0;
    
      // Monophone, 16-bit input hardcoded
      KALDI_ASSERT(sizeof(SampleType) == 2 &&
          "The current GstBufferSource code assumes 16-bit input");
      g_cond_init(&data_cond_);
      g_mutex_init(&lock_);
    }
    
    GstBufferSource::~GstBufferSource() {
      g_cond_clear(&data_cond_);
      g_mutex_clear(&lock_);
      g_async_queue_unref(buf_queue_);
      if (current_buffer_) {
        gst_buffer_unref(current_buffer_);
        current_buffer_ = NULL;
      }
    }
    
    void GstBufferSource::PushBuffer(GstBuffer *buf) {
      g_mutex_lock(&lock_);
      gst_buffer_ref(buf);
      g_async_queue_push(buf_queue_, buf);
      g_cond_signal(&data_cond_);
      g_mutex_unlock(&lock_);
    }
    
    void GstBufferSource::SetEnded(bool ended) {
      ended_ = ended;
      g_mutex_lock(&lock_);
      g_cond_signal(&data_cond_);
      g_mutex_unlock(&lock_);
    }
    
    
    bool GstBufferSource::Read(Vector<BaseFloat> *data) {
      uint32 nsamples_req = data->Dim();  // (16bit) samples requested
      int16 buf[data->Dim()];
      uint32 nbytes_transferred = 0;
    
      while ((nbytes_transferred  < nsamples_req * sizeof(SampleType))) {
        g_mutex_lock(&lock_);
        while ((current_buffer_ == NULL) &&
            !((g_async_queue_length(buf_queue_) == 0) && ended_)) {
          current_buffer_ = reinterpret_cast<GstBuffer*>(g_async_queue_try_pop(buf_queue_));
          if (current_buffer_ == NULL) {
            g_cond_wait(&data_cond_, &lock_);
          }
        }
        g_mutex_unlock(&lock_);
        if (current_buffer_ == NULL) {
          break;
        }
        uint32 nbytes_from_current =
            std::min(nsamples_req * sizeof(SampleType) - nbytes_transferred,
                     (gst_buffer_get_size(current_buffer_) - pos_in_current_buf_));
        uint32 nbytes_extracted =
            gst_buffer_extract(current_buffer_, pos_in_current_buf_,
                               (reinterpret_cast<char *>(buf)) + nbytes_transferred,
                               nbytes_from_current);
        KALDI_ASSERT(nbytes_extracted == nbytes_from_current
                     && "Unexpected number of bytes extracted from Gst buffer");
    
        nbytes_transferred += nbytes_from_current;
        pos_in_current_buf_ += nbytes_from_current;
        if (pos_in_current_buf_ == gst_buffer_get_size(current_buffer_)) {
          // we are done with the current buffer
          gst_buffer_unref(current_buffer_);
          current_buffer_ = NULL;
          pos_in_current_buf_ = 0;
        }
      }
    
      uint32 nsamples_received = nbytes_transferred / sizeof(SampleType);
      for (int i = 0; i < nsamples_received ; ++i) {
        (*data)(i) = static_cast<BaseFloat>(buf[i]);
      }
    
      if (nsamples_received < nsamples_req) {
        data->Resize(nsamples_received, kCopyData);
      }
      return !((g_async_queue_length(buf_queue_) < sizeof(SampleType))
          && ended_
          && (current_buffer_ == NULL));
    }
    }