~bzr-pqm/bzr/bzr.dev

/*

 * delta.h: headers for delta functionality

 *

 * Adapted from GIT for Bazaar by

 *   John Arbash Meinel <john@arbash-meinel.com> (C) 2009

 *

 * This code is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

#ifndef DELTA_H

#define DELTA_H

/* opaque object for delta index */

struct delta_index;

struct source_info {

    const void *buf; /* Pointer to the beginning of source data */

    unsigned long size; /* Total length of source data */

    unsigned long agg_offset; /* Start of source data as part of the

                                 aggregate source */

};

/*

 * create_delta_index: 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 struct delta_index *

create_delta_index(const struct source_info *src,

                   struct delta_index *old);

/*

 * create_delta_index_from_delta: 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 bytes must be in the form of a delta structure, as generated by

 * create_delta(). The generated index will only index the insert bytes, and

 * not any of the control structures.

 */

extern struct delta_index *

create_delta_index_from_delta(const struct source_info *delta,

                              struct delta_index *old);

/*

 * free_delta_index: free the index created by create_delta_index()

 *

 * Given pointer must be what create_delta_index() returned, or NULL.

 */

extern void free_delta_index(struct delta_index *index);

/*

 * sizeof_delta_index: returns memory usage of delta index

 *

 * Given pointer must be what create_delta_index() returned, or NULL.

 */

extern unsigned long sizeof_delta_index(struct 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 void *

create_delta(const struct delta_index *index,

         const void *buf, unsigned long bufsize,

         unsigned long *delta_size, unsigned long max_delta_size);

/* the smallest possible delta size is 3 bytes

 * Target size, Copy command, Copy length

 */

#define DELTA_SIZE_MIN  3

/*

 * This must be called twice on the delta data buffer, first to get the

 * expected source buffer size, and again to get the target buffer size.

 */

static unsigned long

get_delta_hdr_size(unsigned char **datap, const unsigned char *top)

{

    unsigned char *data = *datap;

    unsigned char cmd;

    unsigned long size = 0;

    int i = 0;

    do {

        cmd = *data++;

        size |= (cmd & ~0x80) << i;

        i += 7;

    } while (cmd & 0x80 && data < top);

    *datap = data;

    return size;

}

#endif