bluelib/compress/cstream.h

#ifndef _CSTREAM_H_
#define _CSTREAM_H_

#include <blue/compress/function.h>
#include <blue/core/ringbuffer.h>
#include <stddef.h>

struct b_stream;
struct b_compressor;

enum cstream_flags {
	CSTREAM_CURSOR_MOVED = 0x01u,
};

struct b_cstream {
	enum cstream_flags s_flags;
	struct b_stream *s_endpoint;
	struct b_compressor *s_compressor;
	/* s_in is the input buffer, and s_out is the output buffer.
	 *
	 * the input buffer holds data that will be provided to the
	 * (de)compression function. in compression mode, this data is provided
	 * by the code using the cstream (via b_cstream_write) in decompression
	 * mode, this data is read from s_endpoint.
	 *
	 * the output buffer holds data produced by the (de)compression
	 * function. in compression mode, this data will be written to
	 * s_endpoint. in decompression mode, this data will be returned to the
	 * code using the cstream (via b_cstream_read)
	 *
	 * heavy usage of cstream's compressed sections facility can result
	 * in the input buffer holding uncompressed data while the stream is in
	 * decompression mode. this is handled by the uncompressed read code path.
	 */
	struct b_ringbuffer s_in, s_out;
	enum b_compression_mode s_mode;

	unsigned int s_compression_depth;
	/* tracks the number of compressed bytes that have passed through this
	 * stream in the current section.
	 *
	 * in compression mode, this tracks the number of post-compression bytes
	 * that have been written to the endpoint within the current section,
	 * including any bytes written during end_compression_section()
	 *
	 * in decompression mode, this tracks the number of compressed bytes
	 * that were decompressed while reading the current section. it does not
	 * include any uncompressed bytes that may have been read from the
	 * endpoint while reading a compressed section due to cstream's
	 * read-ahead caching behaviour.
	 */
	size_t s_tx_compressed_bytes;
	/* tracks the number of uncompressed bytes that have passed through this
	 * stream in the current section.
	 *
	 * in compression mode, this tracks the number of bytes given to
	 * b_cstream_write
	 *
	 * in decompression mode, this tracks the number of bytes returned by
	 * b_cstream_read
	 */
	size_t s_tx_uncompressed_bytes;

	/* when the endpoint cursor is moved, the previous cursor position is
	 * saved here so it can be restored later */
	size_t s_cursor;
};

#endif