FLAC__StreamEncoderReadCallback

Signature for the read callback.

A function pointer matching this signature must be passed to FLAC__stream_encoder_init_ogg_stream() if seeking is supported. The supplied function will be called when the encoder needs to read back encoded data. This happens during the metadata callback, when the encoder has to read, modify, and rewrite the metadata (e.g. seekpoints) gathered while encoding. 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__StreamEncoderReadStatus.

Here is an example of a read callback for stdio streams: \code FLAC__StreamEncoderReadStatus read_cb(const FLAC__StreamEncoder *encoder, 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_ENCODER_READ_STATUS_ABORT; else if(*bytes == 0) return FLAC__STREAM_ENCODER_READ_STATUS_END_OF_STREAM; else return FLAC__STREAM_ENCODER_READ_STATUS_CONTINUE; } else return FLAC__STREAM_ENCODER_READ_STATUS_ABORT; } \endcode

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

\param encoder The encoder instance calling the callback. \param buffer A pointer to a location for the callee to store data to be encoded. \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_encoder_set_client_data(). \retval FLAC__StreamEncoderReadStatus The callee's return status.