/*

 * diff-delta code taken from git.git. See diff-delta.c for details.

 *

 */

#ifndef INCLUDE_git_delta_h__

#define INCLUDE_git_delta_h__

#include "common.h"

#include "pack.h"

typedef struct git_delta_index git_delta_index;

/*

 * git_delta_index_init: compute index data from given buffer

 *

 * This returns a pointer to a struct delta_index that should be passed to

 * subsequent create_delta() calls, or to free_delta_index().  A NULL pointer

 * is returned on failure.  The given buffer must not be freed nor altered

 * before free_delta_index() is called.  The returned pointer must be freed

 * using free_delta_index().

 */

extern int git_delta_index_init(

	git_delta_index **out, const void *buf, size_t bufsize);

/*

 * Free the index created by git_delta_index_init()

 */

extern void git_delta_index_free(git_delta_index *index);

/*

 * Returns memory usage of delta index.

 */

extern size_t git_delta_index_size(git_delta_index *index);

/*

 * create_delta: create a delta from given index for the given buffer

 *

 * This function may be called multiple times with different buffers using

 * the same delta_index pointer.  If max_delta_size is non-zero and the

 * resulting delta is to be larger than max_delta_size then NULL is returned.

 * On success, a non-NULL pointer to the buffer with the delta data is

 * returned and *delta_size is updated with its size.  The returned buffer

 * must be freed by the caller.

 */

extern int git_delta_create_from_index(

	void **out,

	size_t *out_size,

	const struct git_delta_index *index,

	const void *buf,

	size_t bufsize,

	size_t max_delta_size);

/*

 * diff_delta: create a delta from source buffer to target buffer

 *

 * If max_delta_size is non-zero and the resulting delta is to be larger

 * than max_delta_size then GIT_EBUFS is returned.  On success, a non-NULL

 * pointer to the buffer with the delta data is returned and *delta_size is

 * updated with its size.  The returned buffer must be freed by the caller.

 */

GIT_INLINE(int) git_delta(

	void **out, size_t *out_len,

	const void *src_buf, size_t src_bufsize,

	const void *trg_buf, size_t trg_bufsize,

	size_t max_delta_size)

{

	git_delta_index *index;

	int error = 0;

	*out = NULL;

	*out_len = 0;

	if ((error = git_delta_index_init(&index, src_buf, src_bufsize)) < 0)

		return error;

	if (index) {

		error = git_delta_create_from_index(out, out_len,

			index, trg_buf, trg_bufsize, max_delta_size);

		git_delta_index_free(index);

	}

	return error;

}

/* the smallest possible delta size is 4 bytes */

#define GIT_DELTA_SIZE_MIN	4

/**

* Apply a git binary delta to recover the original content.

* The caller is responsible for freeing the returned buffer.

*

* @param out the output buffer

* @param out_len the length of the output buffer

* @param base the base to copy from during copy instructions.

* @param base_len number of bytes available at base.

* @param delta the delta to execute copy/insert instructions from.

* @param delta_len total number of bytes in the delta.

* @return 0 on success or an error code

*/

extern int git_delta_apply(

	void **out,

	size_t *out_len,

	const unsigned char *base,

	size_t base_len,

	const unsigned char *delta,

	size_t delta_len);

/**

* Read the header of a git binary delta.

*

* @param base_out pointer to store the base size field.

* @param result_out pointer to store the result size field.

* @param delta the delta to execute copy/insert instructions from.

* @param delta_len total number of bytes in the delta.

* @return 0 on success or an error code

*/

extern int git_delta_read_header(

	size_t *base_out,

	size_t *result_out,

	const unsigned char *delta,

	size_t delta_len);

/**

 * Read the header of a git binary delta

 *

 * This variant reads just enough from the packfile stream to read the

 * delta header.

 */

extern int git_delta_read_header_fromstream(

	size_t *base_out,

	size_t *result_out,

	git_packfile_stream *stream);

#endif