Method decode_samples

src/world/sound_world_al.cpp:166–271

Decodes a block of samples of size BLOCK_MS or less, and feeds it to AL. Returns the number of samples that have been decoded.

	/// Decodes a block of samples of size BLOCK_MS or less, and feeds it to AL.
	/// Returns the number of samples that have been decoded.
	u32 decode_samples()
	{
		if (!_stream)
			return 0;

		if (_resource->stream_format == StreamFormat::OGG) {
			const OggStreamMetadata *ogg = (OggStreamMetadata *)sound_resource::stream_metadata(_resource);
			int used;
			int skip_n = 0;

			// Open the stream.
			if (_stream_data == NULL) {
				const u32 stream_mem_size = 0
					+ sizeof(stb_vorbis_alloc) + alignof(stb_vorbis_alloc)
					+ ogg->alloc_buffer_size
					+ ogg->headers_size
					+ ogg->max_frame_size
					+ _block_size*2 + alignof(f32)
					;
				_stream_data = default_allocator().allocate(stream_mem_size);

				_vorbis_alloc = (stb_vorbis_alloc *)memory::align_top(_stream_data, alignof(stb_vorbis_alloc));
				_vorbis_alloc->alloc_buffer = (char *)&_vorbis_alloc[1];
				_vorbis_alloc->alloc_buffer_length_in_bytes = ogg->alloc_buffer_size;

				_vorbis_headers = (unsigned char *)&_vorbis_alloc[1] + ogg->alloc_buffer_size;

				_stream_encoded = (unsigned char *)_vorbis_headers + ogg->headers_size;
				_stream_decoded = (u8 *)memory::align_top(_stream_encoded + ogg->max_frame_size, alignof(f32));
				_stream_pos = 0;

				_stream->read(_vorbis_headers, ogg->headers_size);
				skip_n = ogg->num_samples_skip;
			}

			if (_vorbis == NULL) {
				int error;
				_vorbis = stb_vorbis_open_pushdata(_vorbis_headers, ogg->headers_size, &used, &error, _vorbis_alloc);
				CE_ENSURE(error == VORBIS__no_error);
				CE_ENSURE(_vorbis != NULL);
				CE_ENSURE(used == ogg->headers_size);
			}

			// Decode _block_size samples or less.
			f32 *dec = (f32 *)_stream_decoded;
			u32 tot_n = 0;
			while (tot_n < _block_samples) {
				float **output;
				int n;
				int q = ogg->max_frame_size;

			retry:
				if (q > int(_stream->size() - _stream_pos))
					q = _stream->size() - _stream_pos;
				if ((int)_stream_pos < q)
					_stream_pos += _stream->read(&_stream_encoded[_stream_pos], q - _stream_pos);

				used = stb_vorbis_decode_frame_pushdata(_vorbis