Function _fetchChunk

static/js/chunkedAudioEngine.js:192–223

(chunkIdx)

  // Returns a Promise<Map<name, AudioBuffer>>. Deduplicates: if a fetch for
  // chunkIdx is already in flight, returns the same promise.
  function _fetchChunk(chunkIdx) {
    const hit = _cache.get(chunkIdx);
    if (hit) return hit.promise;

    const entry = { promise: null, result: null };
    entry.promise = (async () => {
      const pairs = await Promise.all(
        [...stemMap.entries()]
          .filter(([, s]) => s.header)
          .map(async ([name, stem]) => {
            try {
              const pcm = await _fetchPcm(stem, chunkIdx);
              if (!pcm) return [name, null];
              return [name, _pcmToAudioBuffer(ctx, pcm, stem.header)];
            } catch (e) {
              console.warn(`[chunked] chunk ${chunkIdx} stem ${name}:`, e);
              return [name, null];
            }
          })
      );
      const map = new Map(pairs.filter(([, b]) => b));
      entry.result = map;
      // Keep at most the previous chunk + current in cache to bound memory.
      for (const k of _cache.keys()) {
        if (k < chunkIdx - 1) _cache.delete(k);
      }
      return map;
    })();

    _cache.set(chunkIdx, entry);
    return entry.promise;
  }

  // --- node lifecycle ---