buffer-helper.js

/**
 * Buffer Helper class, providing methods dealing buffer length retrieval
*/


class BufferHelper {

  static bufferInfo(media, pos,maxHoleDuration) {
    if (media) {
      var vbuffered = media.buffered, buffered = [],i;
      for (i = 0; i < vbuffered.length; i++) {
        buffered.push({start: vbuffered.start(i), end: vbuffered.end(i)});
      }
      return this.bufferedInfo(buffered,pos,maxHoleDuration);
    } else {
      return {len: 0, start: 0, end: 0, nextStart : undefined} ;
    }
  }

  static bufferedInfo(buffered,pos,maxHoleDuration) {
    var buffered2 = [],
        // bufferStart and bufferEnd are buffer boundaries around current video position
        bufferLen,bufferStart, bufferEnd,bufferStartNext,i;
    // sort on buffer.start/smaller end (IE does not always return sorted buffered range)
    buffered.sort(function (a, b) {
      var diff = a.start - b.start;
      if (diff) {
        return diff;
      } else {
        return b.end - a.end;
      }
    });
    // there might be some small holes between buffer time range
    // consider that holes smaller than maxHoleDuration are irrelevant and build another
    // buffer time range representations that discards those holes
    for (i = 0; i < buffered.length; i++) {
      var buf2len = buffered2.length;
      if(buf2len) {
        var buf2end = buffered2[buf2len - 1].end;
        // if small hole (value between 0 or maxHoleDuration ) or overlapping (negative)
        if((buffered[i].start - buf2end) < maxHoleDuration) {
          // merge overlapping time ranges
          // update lastRange.end only if smaller than item.end
          // e.g.  [ 1, 15] with  [ 2,8] => [ 1,15] (no need to modify lastRange.end)
          // whereas [ 1, 8] with  [ 2,15] => [ 1,15] ( lastRange should switch from [1,8] to [1,15])
          if(buffered[i].end > buf2end) {
            buffered2[buf2len - 1].end = buffered[i].end;
          }
        } else {
          // big hole
          buffered2.push(buffered[i]);
        }
      } else {
        // first value
        buffered2.push(buffered[i]);
      }
    }
    for (i = 0, bufferLen = 0, bufferStart = bufferEnd = pos; i < buffered2.length; i++) {
      var start =  buffered2[i].start,
          end = buffered2[i].end;
      //logger.log('buf start/end:' + buffered.start(i) + '/' + buffered.end(i));
      if ((pos + maxHoleDuration) >= start && pos < end) {
        // play position is inside this buffer TimeRange, retrieve end of buffer position and buffer length
        bufferStart = start;
        bufferEnd = end;
        bufferLen = bufferEnd - pos;
      } else if ((pos + maxHoleDuration) < start) {
        bufferStartNext = start;
        break;
      }
    }
    return {len: bufferLen, start: bufferStart, end: bufferEnd, nextStart : bufferStartNext};
  }

}

export default BufferHelper;