FLAC__StreamDecoderReadCallback

Signature for the read callback.

A function pointer matching this signature must be passed to FLAC__stream_decoder_init*_stream(). The supplied function will be called when the decoder needs more input data. The address of the buffer to be filled is supplied, along with the number of bytes the buffer can hold. The callback may choose to supply less data and modify the byte count but must be careful not to overflow the buffer. The callback then returns a status code chosen from FLAC__StreamDecoderReadStatus.

Here is an example of a read callback for stdio streams: \code FLAC__StreamDecoderReadStatus read_cb(const FLAC__StreamDecoder *decoder, FLAC__byte buffer[], size_t *bytes, void *client_data) { FILE *file = ((MyClientData*)client_data)->file; if(*bytes > 0) { *bytes = fread(buffer, sizeof(FLAC__byte), *bytes, file); if(ferror(file)) return FLAC__STREAM_DECODER_READ_STATUS_ABORT; else if(*bytes == 0) return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM; else return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE; } else return FLAC__STREAM_DECODER_READ_STATUS_ABORT; } \endcode

\note In general, FLAC__StreamDecoder functions which change the state should not be called on the \a decoder while in the callback.

\param decoder The decoder instance calling the callback. \param buffer A pointer to a location for the callee to store data to be decoded. \param bytes A pointer to the size of the buffer. On entry to the callback, it contains the maximum number of bytes that may be stored in \a buffer. The callee must set it to the actual number of bytes stored (0 in case of error or end-of-stream) before returning. \param client_data The callee's client data set through FLAC__stream_decoder_init_*(). \retval FLAC__StreamDecoderReadStatus The callee's return status. Note that the callback should return \c FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM if and only if zero bytes were read and there is no more data to be read.