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Diffstat (limited to 'bzrlib/delta.h')
| -rw-r--r-- | bzrlib/delta.h | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/bzrlib/delta.h b/bzrlib/delta.h new file mode 100644 index 0000000..37668f4 --- /dev/null +++ b/bzrlib/delta.h @@ -0,0 +1,154 @@ +/* + * 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 */ +}; + +/* result type for functions that have multiple failure modes */ +typedef enum { + DELTA_OK, /* Success */ + DELTA_OUT_OF_MEMORY, /* Could not allocate required memory */ + DELTA_INDEX_NEEDED, /* A delta_index must be passed */ + DELTA_SOURCE_EMPTY, /* A source_info had no content */ + DELTA_SOURCE_BAD, /* A source_info had invalid or corrupt content */ + DELTA_BUFFER_EMPTY, /* A buffer pointer and size */ + DELTA_SIZE_TOO_BIG, /* Delta data is larger than the max requested */ +} delta_result; + + +/* + * create_delta_index: compute index data from given buffer + * + * Returns a delta_result status, when DELTA_OK then *fresh is set to a struct + * delta_index that should be passed to subsequent create_delta() calls, or to + * free_delta_index(). Other values are a failure, and *fresh is unset. + * The given buffer must not be freed nor altered before free_delta_index() is + * called. The resultant struct must be freed using free_delta_index(). + * + * :param max_bytes_to_index: Limit the number of regions to sample to this + * amount of text. We will store at most max_bytes_to_index / RABIN_WINDOW + * pointers into the source text. Useful if src can be unbounded in size, + * and you are willing to trade match accuracy for peak memory. + */ +extern delta_result +create_delta_index(const struct source_info *src, + struct delta_index *old, + struct delta_index **fresh, + int max_bytes_to_index); + + +/* + * create_delta_index_from_delta: compute index data from given buffer + * + * Returns a delta_result status, when DELTA_OK then *fresh is set to a struct + * delta_index that should be passed to subsequent create_delta() calls, or to + * free_delta_index(). Other values are a failure, and *fresh is unset. + * 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 delta_result +create_delta_index_from_delta(const struct source_info *delta, + struct delta_index *old, + struct delta_index **fresh); +/* + * 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 DELTA_SIZE_TOO_BIG + * is returned. Otherwise on success, DELTA_OK is returned and *delta_data is + * set to a new buffer with the delta data and *delta_size is updated with its + * size. That buffer must be freed by the caller. + */ +extern delta_result +create_delta(const struct delta_index *index, + const void *buf, unsigned long bufsize, + unsigned long *delta_size, unsigned long max_delta_size, + void **delta_data); + +/* 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; +} + +/* + * Return the basic information about a given delta index. + * :param index: The delta_index object + * :param pos: The offset in the entry list. Start at 0, and walk until you get + * 0 as a return code. + * :param global_offset: return value, distance to the beginning of all sources + * :param hash_val: return value, the RABIN hash associated with this pointer + * :param hash_offset: Location for this entry in the hash array. + * :return: 1 if pos != -1 (there was data produced) + */ +extern int +get_entry_summary(const struct delta_index *index, int pos, + unsigned int *text_offset, unsigned int *hash_val); + +/* + * Determine what entry index->hash[X] points to. + */ +extern int +get_hash_offset(const struct delta_index *index, int pos, + unsigned int *entry_offset); + +/* + * Compute the rabin_hash of the given data, it is assumed the data is at least + * RABIN_WINDOW wide (16 bytes). + */ +extern unsigned int +rabin_hash(const unsigned char *data); + +#endif |