# All files / src/utils buffer-helper.js

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     /**
     * @module BufferHelper
     *
     * Providing methods dealing with buffer length retrieval for example.
     *
     * In general, a helper around HTML5 MediaElement TimeRanges gathered from `buffered` property.
     *
     * Also @see https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/buffered
    */

    export class BufferHelper {
      /**
       * Return true if `media`'s buffered include `position`
       * @param {HTMLMediaElement|SourceBuffer} media
       * @param {number} position
       * @returns {boolean}
       */
      static isBuffered (media, position) {
        try {
          if (media) {
            let buffered = media.buffered;
            for (let i = 0; i < buffered.length; i++) {
              if (position >= buffered.start(i) && position <= buffered.end(i)) {
                return true;
              }
            }
          }
        } catch (error) {
          // this is to catch
          // InvalidStateError: Failed to read the 'buffered' property from 'SourceBuffer':
          // This SourceBuffer has been removed from the parent media source
        }
        return false;
      }

      static bufferInfo (media, pos, maxHoleDuration) {
        try {
          if (media) {
            let 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);
          }
        } catch (error) {
          // this is to catch
          // InvalidStateError: Failed to read the 'buffered' property from 'SourceBuffer':
          // This SourceBuffer has been removed from the parent media source
        }
        return { len: 0, start: pos, end: pos, nextStart: undefined };
      }

      static bufferedInfo (buffered, pos, maxHoleDuration) {
        let 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) {
          let 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++) {
          let buf2len = buffered2.length;
          if (buf2len) {
            let 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++) {
          let 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 };
      }
    }