[thirdparty/git.git] / diff-delta.c

/*
 * diff-delta.c: generate a delta between two buffers
 *
 *  Many parts of this file have been lifted from LibXDiff version 0.10.
 *  http://www.xmailserver.org/xdiff-lib.html
 *
 *  LibXDiff was written by Davide Libenzi <davidel@xmailserver.org>
 *  Copyright (C) 2003	Davide Libenzi
 *
 *  Many mods for GIT usage by Nicolas Pitre <nico@cam.org>, (C) 2005.
 *
 *  This file is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  Use of this within git automatically means that the LGPL
 *  licensing gets turned into GPLv2 within this project.
 */

#include <stdlib.h>
#include <string.h>
#include "delta.h"


/* maximum hash entry list for the same hash bucket */
#define HASH_LIMIT 64

#define RABIN_SHIFT 23
#define RABIN_WINDOW 16

static const unsigned int T[256] = {
	0x00000000, 0xab59b4d1, 0x56b369a2, 0xfdeadd73, 0x063f6795, 0xad66d344,
	0x508c0e37, 0xfbd5bae6, 0x0c7ecf2a, 0xa7277bfb, 0x5acda688, 0xf1941259,
	0x0a41a8bf, 0xa1181c6e, 0x5cf2c11d, 0xf7ab75cc, 0x18fd9e54, 0xb3a42a85,
	0x4e4ef7f6, 0xe5174327, 0x1ec2f9c1, 0xb59b4d10, 0x48719063, 0xe32824b2,
	0x1483517e, 0xbfdae5af, 0x423038dc, 0xe9698c0d, 0x12bc36eb, 0xb9e5823a,
	0x440f5f49, 0xef56eb98, 0x31fb3ca8, 0x9aa28879, 0x6748550a, 0xcc11e1db,
	0x37c45b3d, 0x9c9defec, 0x6177329f, 0xca2e864e, 0x3d85f382, 0x96dc4753,
	0x6b369a20, 0xc06f2ef1, 0x3bba9417, 0x90e320c6, 0x6d09fdb5, 0xc6504964,
	0x2906a2fc, 0x825f162d, 0x7fb5cb5e, 0xd4ec7f8f, 0x2f39c569, 0x846071b8,
	0x798aaccb, 0xd2d3181a, 0x25786dd6, 0x8e21d907, 0x73cb0474, 0xd892b0a5,
	0x23470a43, 0x881ebe92, 0x75f463e1, 0xdeadd730, 0x63f67950, 0xc8afcd81,
	0x354510f2, 0x9e1ca423, 0x65c91ec5, 0xce90aa14, 0x337a7767, 0x9823c3b6,
	0x6f88b67a, 0xc4d102ab, 0x393bdfd8, 0x92626b09, 0x69b7d1ef, 0xc2ee653e,
	0x3f04b84d, 0x945d0c9c, 0x7b0be704, 0xd05253d5, 0x2db88ea6, 0x86e13a77,
	0x7d348091, 0xd66d3440, 0x2b87e933, 0x80de5de2, 0x7775282e, 0xdc2c9cff,
	0x21c6418c, 0x8a9ff55d, 0x714a4fbb, 0xda13fb6a, 0x27f92619, 0x8ca092c8,
	0x520d45f8, 0xf954f129, 0x04be2c5a, 0xafe7988b, 0x5432226d, 0xff6b96bc,
	0x02814bcf, 0xa9d8ff1e, 0x5e738ad2, 0xf52a3e03, 0x08c0e370, 0xa39957a1,
	0x584ced47, 0xf3155996, 0x0eff84e5, 0xa5a63034, 0x4af0dbac, 0xe1a96f7d,
	0x1c43b20e, 0xb71a06df, 0x4ccfbc39, 0xe79608e8, 0x1a7cd59b, 0xb125614a,
	0x468e1486, 0xedd7a057, 0x103d7d24, 0xbb64c9f5, 0x40b17313, 0xebe8c7c2,
	0x16021ab1, 0xbd5bae60, 0x6cb54671, 0xc7ecf2a0, 0x3a062fd3, 0x915f9b02,
	0x6a8a21e4, 0xc1d39535, 0x3c394846, 0x9760fc97, 0x60cb895b, 0xcb923d8a,
	0x3678e0f9, 0x9d215428, 0x66f4eece, 0xcdad5a1f, 0x3047876c, 0x9b1e33bd,
	0x7448d825, 0xdf116cf4, 0x22fbb187, 0x89a20556, 0x7277bfb0, 0xd92e0b61,
	0x24c4d612, 0x8f9d62c3, 0x7836170f, 0xd36fa3de, 0x2e857ead, 0x85dcca7c,
	0x7e09709a, 0xd550c44b, 0x28ba1938, 0x83e3ade9, 0x5d4e7ad9, 0xf617ce08,
	0x0bfd137b, 0xa0a4a7aa, 0x5b711d4c, 0xf028a99d, 0x0dc274ee, 0xa69bc03f,
	0x5130b5f3, 0xfa690122, 0x0783dc51, 0xacda6880, 0x570fd266, 0xfc5666b7,
	0x01bcbbc4, 0xaae50f15, 0x45b3e48d, 0xeeea505c, 0x13008d2f, 0xb85939fe,
	0x438c8318, 0xe8d537c9, 0x153feaba, 0xbe665e6b, 0x49cd2ba7, 0xe2949f76,
	0x1f7e4205, 0xb427f6d4, 0x4ff24c32, 0xe4abf8e3, 0x19412590, 0xb2189141,
	0x0f433f21, 0xa41a8bf0, 0x59f05683, 0xf2a9e252, 0x097c58b4, 0xa225ec65,
	0x5fcf3116, 0xf49685c7, 0x033df00b, 0xa86444da, 0x558e99a9, 0xfed72d78,
	0x0502979e, 0xae5b234f, 0x53b1fe3c, 0xf8e84aed, 0x17bea175, 0xbce715a4,
	0x410dc8d7, 0xea547c06, 0x1181c6e0, 0xbad87231, 0x4732af42, 0xec6b1b93,
	0x1bc06e5f, 0xb099da8e, 0x4d7307fd, 0xe62ab32c, 0x1dff09ca, 0xb6a6bd1b,
	0x4b4c6068, 0xe015d4b9, 0x3eb80389, 0x95e1b758, 0x680b6a2b, 0xc352defa,
	0x3887641c, 0x93ded0cd, 0x6e340dbe, 0xc56db96f, 0x32c6cca3, 0x999f7872,
	0x6475a501, 0xcf2c11d0, 0x34f9ab36, 0x9fa01fe7, 0x624ac294, 0xc9137645,
	0x26459ddd, 0x8d1c290c, 0x70f6f47f, 0xdbaf40ae, 0x207afa48, 0x8b234e99,
	0x76c993ea, 0xdd90273b, 0x2a3b52f7, 0x8162e626, 0x7c883b55, 0xd7d18f84,
	0x2c043562, 0x875d81b3, 0x7ab75cc0, 0xd1eee811
};

static const unsigned int U[256] = {
	0x00000000, 0x7eb5200d, 0x5633f4cb, 0x2886d4c6, 0x073e5d47, 0x798b7d4a,
	0x510da98c, 0x2fb88981, 0x0e7cba8e, 0x70c99a83, 0x584f4e45, 0x26fa6e48,
	0x0942e7c9, 0x77f7c7c4, 0x5f711302, 0x21c4330f, 0x1cf9751c, 0x624c5511,
	0x4aca81d7, 0x347fa1da, 0x1bc7285b, 0x65720856, 0x4df4dc90, 0x3341fc9d,
	0x1285cf92, 0x6c30ef9f, 0x44b63b59, 0x3a031b54, 0x15bb92d5, 0x6b0eb2d8,
	0x4388661e, 0x3d3d4613, 0x39f2ea38, 0x4747ca35, 0x6fc11ef3, 0x11743efe,
	0x3eccb77f, 0x40799772, 0x68ff43b4, 0x164a63b9, 0x378e50b6, 0x493b70bb,
	0x61bda47d, 0x1f088470, 0x30b00df1, 0x4e052dfc, 0x6683f93a, 0x1836d937,
	0x250b9f24, 0x5bbebf29, 0x73386bef, 0x0d8d4be2, 0x2235c263, 0x5c80e26e,
	0x740636a8, 0x0ab316a5, 0x2b7725aa, 0x55c205a7, 0x7d44d161, 0x03f1f16c,
	0x2c4978ed, 0x52fc58e0, 0x7a7a8c26, 0x04cfac2b, 0x73e5d470, 0x0d50f47d,
	0x25d620bb, 0x5b6300b6, 0x74db8937, 0x0a6ea93a, 0x22e87dfc, 0x5c5d5df1,
	0x7d996efe, 0x032c4ef3, 0x2baa9a35, 0x551fba38, 0x7aa733b9, 0x041213b4,
	0x2c94c772, 0x5221e77f, 0x6f1ca16c, 0x11a98161, 0x392f55a7, 0x479a75aa,
	0x6822fc2b, 0x1697dc26, 0x3e1108e0, 0x40a428ed, 0x61601be2, 0x1fd53bef,
	0x3753ef29, 0x49e6cf24, 0x665e46a5, 0x18eb66a8, 0x306db26e, 0x4ed89263,
	0x4a173e48, 0x34a21e45, 0x1c24ca83, 0x6291ea8e, 0x4d29630f, 0x339c4302,
	0x1b1a97c4, 0x65afb7c9, 0x446b84c6, 0x3adea4cb, 0x1258700d, 0x6ced5000,
	0x4355d981, 0x3de0f98c, 0x15662d4a, 0x6bd30d47, 0x56ee4b54, 0x285b6b59,
	0x00ddbf9f, 0x7e689f92, 0x51d01613, 0x2f65361e, 0x07e3e2d8, 0x7956c2d5,
	0x5892f1da, 0x2627d1d7, 0x0ea10511, 0x7014251c, 0x5facac9d, 0x21198c90,
	0x099f5856, 0x772a785b, 0x4c921c31, 0x32273c3c, 0x1aa1e8fa, 0x6414c8f7,
	0x4bac4176, 0x3519617b, 0x1d9fb5bd, 0x632a95b0, 0x42eea6bf, 0x3c5b86b2,
	0x14dd5274, 0x6a687279, 0x45d0fbf8, 0x3b65dbf5, 0x13e30f33, 0x6d562f3e,
	0x506b692d, 0x2ede4920, 0x06589de6, 0x78edbdeb, 0x5755346a, 0x29e01467,
	0x0166c0a1, 0x7fd3e0ac, 0x5e17d3a3, 0x20a2f3ae, 0x08242768, 0x76910765,
	0x59298ee4, 0x279caee9, 0x0f1a7a2f, 0x71af5a22, 0x7560f609, 0x0bd5d604,
	0x235302c2, 0x5de622cf, 0x725eab4e, 0x0ceb8b43, 0x246d5f85, 0x5ad87f88,
	0x7b1c4c87, 0x05a96c8a, 0x2d2fb84c, 0x539a9841, 0x7c2211c0, 0x029731cd,
	0x2a11e50b, 0x54a4c506, 0x69998315, 0x172ca318, 0x3faa77de, 0x411f57d3,
	0x6ea7de52, 0x1012fe5f, 0x38942a99, 0x46210a94, 0x67e5399b, 0x19501996,
	0x31d6cd50, 0x4f63ed5d, 0x60db64dc, 0x1e6e44d1, 0x36e89017, 0x485db01a,
	0x3f77c841, 0x41c2e84c, 0x69443c8a, 0x17f11c87, 0x38499506, 0x46fcb50b,
	0x6e7a61cd, 0x10cf41c0, 0x310b72cf, 0x4fbe52c2, 0x67388604, 0x198da609,
	0x36352f88, 0x48800f85, 0x6006db43, 0x1eb3fb4e, 0x238ebd5d, 0x5d3b9d50,
	0x75bd4996, 0x0b08699b, 0x24b0e01a, 0x5a05c017, 0x728314d1, 0x0c3634dc,
	0x2df207d3, 0x534727de, 0x7bc1f318, 0x0574d315, 0x2acc5a94, 0x54797a99,
	0x7cffae5f, 0x024a8e52, 0x06852279, 0x78300274, 0x50b6d6b2, 0x2e03f6bf,
	0x01bb7f3e, 0x7f0e5f33, 0x57888bf5, 0x293dabf8, 0x08f998f7, 0x764cb8fa,
	0x5eca6c3c, 0x207f4c31, 0x0fc7c5b0, 0x7172e5bd, 0x59f4317b, 0x27411176,
	0x1a7c5765, 0x64c97768, 0x4c4fa3ae, 0x32fa83a3, 0x1d420a22, 0x63f72a2f,
	0x4b71fee9, 0x35c4dee4, 0x1400edeb, 0x6ab5cde6, 0x42331920, 0x3c86392d,
	0x133eb0ac, 0x6d8b90a1, 0x450d4467, 0x3bb8646a
};

struct index_entry {
	const unsigned char *ptr;
	unsigned int val;
	struct index_entry *next;
};

struct delta_index {
	const void *src_buf;
	unsigned long src_size;
	unsigned int hash_mask;
	struct index_entry *hash[0];
};

struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
{
	unsigned int i, hsize, hmask, entries, prev_val, *hash_count;
	const unsigned char *data, *buffer = buf;
	struct delta_index *index;
	struct index_entry *entry, **hash;
	void *mem;
	unsigned long memsize;

	if (!buf || !bufsize)
		return NULL;

	/* Determine index hash size.  Note that indexing skips the
	   first byte to allow for optimizing the rabin polynomial
	   initialization in create_delta(). */
	entries = (bufsize - 1)  / RABIN_WINDOW;
	hsize = entries / 4;
	for (i = 4; (1 << i) < hsize && i < 31; i++);
	hsize = 1 << i;
	hmask = hsize - 1;

	/* allocate lookup index */
	memsize = sizeof(*index) +
		  sizeof(*hash) * hsize +
		  sizeof(*entry) * entries;
	mem = malloc(memsize);
	if (!mem)
		return NULL;
	index = mem;
	mem = index + 1;
	hash = mem;
	mem = hash + hsize;
	entry = mem;

	index->src_buf = buf;
	index->src_size = bufsize;
	index->hash_mask = hmask;
	memset(hash, 0, hsize * sizeof(*hash));

	/* allocate an array to count hash entries */
	hash_count = calloc(hsize, sizeof(*hash_count));
	if (!hash_count) {
		free(index);
		return NULL;
	}

	/* then populate the index */
	prev_val = ~0;
	for (data = buffer + entries * RABIN_WINDOW - RABIN_WINDOW;
	     data >= buffer;
	     data -= RABIN_WINDOW) {
		unsigned int val = 0;
		for (i = 1; i <= RABIN_WINDOW; i++)
			val = ((val << 8) | data[i]) ^ T[val >> RABIN_SHIFT];
		if (val == prev_val) {
			/* keep the lowest of consecutive identical blocks */
			entry[-1].ptr = data + RABIN_WINDOW;
		} else {
			prev_val = val;
			i = val & hmask;
			entry->ptr = data + RABIN_WINDOW;
			entry->val = val;
			entry->next = hash[i];
			hash[i] = entry++;
			hash_count[i]++;
		}
	}

	/*
	 * Determine a limit on the number of entries in the same hash
	 * bucket.  This guard us against patological data sets causing
	 * really bad hash distribution with most entries in the same hash
	 * bucket that would bring us to O(m*n) computing costs (m and n
	 * corresponding to reference and target buffer sizes).
	 *
	 * Make sure none of the hash buckets has more entries than
	 * we're willing to test.  Otherwise we cull the entry list
	 * uniformly to still preserve a good repartition across
	 * the reference buffer.
	 */
	for (i = 0; i < hsize; i++) {
		if (hash_count[i] < HASH_LIMIT)
			continue;
		entry = hash[i];
		do {
			struct index_entry *keep = entry;
			int skip = hash_count[i] / HASH_LIMIT / 2;
			do {
				entry = entry->next;
			} while(--skip && entry);
			keep->next = entry;
		} while(entry);
	}
	free(hash_count);

	return index;
}

void free_delta_index(struct delta_index *index)
{
	free(index);
}

/*
 * The maximum size for any opcode sequence, including the initial header
 * plus rabin window plus biggest copy.
 */
#define MAX_OP_SIZE	(5 + 5 + 1 + RABIN_WINDOW + 7)

void *
create_delta(const struct delta_index *index,
	     const void *trg_buf, unsigned long trg_size,
	     unsigned long *delta_size, unsigned long max_size)
{
	unsigned int i, outpos, outsize, val;
	int inscnt;
	const unsigned char *ref_data, *ref_top, *data, *top;
	unsigned char *out;

	if (!trg_buf || !trg_size)
		return NULL;

	outpos = 0;
	outsize = 8192;
	if (max_size && outsize >= max_size)
		outsize = max_size + MAX_OP_SIZE + 1;
	out = malloc(outsize);
	if (!out)
		return NULL;

	/* store reference buffer size */
	i = index->src_size;
	while (i >= 0x80) {
		out[outpos++] = i | 0x80;
		i >>= 7;
	}
	out[outpos++] = i;

	/* store target buffer size */
	i = trg_size;
	while (i >= 0x80) {
		out[outpos++] = i | 0x80;
		i >>= 7;
	}
	out[outpos++] = i;

	ref_data = index->src_buf;
	ref_top = ref_data + index->src_size;
	data = trg_buf;
	top = trg_buf + trg_size;

	outpos++;
	val = 0;
	for (i = 0; i < RABIN_WINDOW && data < top; i++, data++) {
		out[outpos++] = *data;
		val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT];
	}
	inscnt = i;

	while (data < top) {
		unsigned int moff = 0, msize = 0;
		struct index_entry *entry;
		val ^= U[data[-RABIN_WINDOW]];
		val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT];
		i = val & index->hash_mask;
		for (entry = index->hash[i]; entry; entry = entry->next) {
			const unsigned char *ref = entry->ptr;
			const unsigned char *src = data;
			unsigned int ref_size = ref_top - ref;
			if (entry->val != val)
				continue;
			if (ref_size > top - src)
				ref_size = top - src;
			if (ref_size > 0x10000)
				ref_size = 0x10000;
			if (ref_size <= msize)
				break;
			while (ref_size-- && *src++ == *ref)
				ref++;
			if (msize < ref - entry->ptr) {
				/* this is our best match so far */
				msize = ref - entry->ptr;
				moff = entry->ptr - ref_data;
			}
		}

		if (msize < 4) {
			if (!inscnt)
				outpos++;
			out[outpos++] = *data++;
			inscnt++;
			if (inscnt == 0x7f) {
				out[outpos - inscnt - 1] = inscnt;
				inscnt = 0;
			}
		} else {
			unsigned char *op;

			if (msize >= RABIN_WINDOW) {
				const unsigned char *sk;
				sk = data + msize - RABIN_WINDOW;
				val = 0;
				for (i = 0; i < RABIN_WINDOW; i++)
					val = ((val << 8) | *sk++) ^ T[val >> RABIN_SHIFT];
			} else {
				const unsigned char *sk = data + 1;
				for (i = 1; i < msize; i++) {
					val ^= U[sk[-RABIN_WINDOW]];
					val = ((val << 8) | *sk++) ^ T[val >> RABIN_SHIFT];
				}
			}

			if (inscnt) {
				while (moff && ref_data[moff-1] == data[-1]) {
					if (msize == 0x10000)
						break;
					/* we can match one byte back */
					msize++;
					moff--;
					data--;
					outpos--;
					if (--inscnt)
						continue;
					outpos--;  /* remove count slot */
					inscnt--;  /* make it -1 */
					break;
				}
				out[outpos - inscnt - 1] = inscnt;
				inscnt = 0;
			}

			data += msize;
			op = out + outpos++;
			i = 0x80;

			if (moff & 0xff) { out[outpos++] = moff; i |= 0x01; }
			moff >>= 8;
			if (moff & 0xff) { out[outpos++] = moff; i |= 0x02; }
			moff >>= 8;
			if (moff & 0xff) { out[outpos++] = moff; i |= 0x04; }
			moff >>= 8;
			if (moff & 0xff) { out[outpos++] = moff; i |= 0x08; }

			if (msize & 0xff) { out[outpos++] = msize; i |= 0x10; }
			msize >>= 8;
			if (msize & 0xff) { out[outpos++] = msize; i |= 0x20; }

			*op = i;
		}

		if (outpos >= outsize - MAX_OP_SIZE) {
			void *tmp = out;
			outsize = outsize * 3 / 2;
			if (max_size && outsize >= max_size)
				outsize = max_size + MAX_OP_SIZE + 1;
			if (max_size && outpos > max_size)
				break;
			out = realloc(out, outsize);
			if (!out) {
				free(tmp);
				return NULL;
			}
		}
	}

	if (inscnt)
		out[outpos - inscnt - 1] = inscnt;

	if (max_size && outpos > max_size) {
		free(out);
		return NULL;
	}

	*delta_size = outpos;
	return out;
}
Commit	Line	Data
a310d434 NP	1	/*
	2	* diff-delta.c: generate a delta between two buffers
	3	*
	4	* Many parts of this file have been lifted from LibXDiff version 0.10.
	5	* http://www.xmailserver.org/xdiff-lib.html
	6	*
	7	* LibXDiff was written by Davide Libenzi <davidel@xmailserver.org>
	8	* Copyright (C) 2003 Davide Libenzi
	9	*
	10	* Many mods for GIT usage by Nicolas Pitre <nico@cam.org>, (C) 2005.
	11	*
	12	* This file is free software; you can redistribute it and/or
	13	* modify it under the terms of the GNU Lesser General Public
	14	* License as published by the Free Software Foundation; either
	15	* version 2.1 of the License, or (at your option) any later version.
	16	*
	17	* Use of this within git automatically means that the LGPL
	18	* licensing gets turned into GPLv2 within this project.
	19	*/
	20
	21	#include <stdlib.h>
8e1454b5	22	#include <string.h>
a310d434 NP	23	#include "delta.h"
	24
	25
08abe669 NP	26	/* maximum hash entry list for the same hash bucket */
08abe669 NP	27	#define HASH_LIMIT 64
a310d434	28
3dc5a9e4 NP	29	#define RABIN_SHIFT 23
	30	#define RABIN_WINDOW 16
	31
	32	static const unsigned int T[256] = {
	33	0x00000000, 0xab59b4d1, 0x56b369a2, 0xfdeadd73, 0x063f6795, 0xad66d344,
	34	0x508c0e37, 0xfbd5bae6, 0x0c7ecf2a, 0xa7277bfb, 0x5acda688, 0xf1941259,
	35	0x0a41a8bf, 0xa1181c6e, 0x5cf2c11d, 0xf7ab75cc, 0x18fd9e54, 0xb3a42a85,
	36	0x4e4ef7f6, 0xe5174327, 0x1ec2f9c1, 0xb59b4d10, 0x48719063, 0xe32824b2,
	37	0x1483517e, 0xbfdae5af, 0x423038dc, 0xe9698c0d, 0x12bc36eb, 0xb9e5823a,
	38	0x440f5f49, 0xef56eb98, 0x31fb3ca8, 0x9aa28879, 0x6748550a, 0xcc11e1db,
	39	0x37c45b3d, 0x9c9defec, 0x6177329f, 0xca2e864e, 0x3d85f382, 0x96dc4753,
	40	0x6b369a20, 0xc06f2ef1, 0x3bba9417, 0x90e320c6, 0x6d09fdb5, 0xc6504964,
	41	0x2906a2fc, 0x825f162d, 0x7fb5cb5e, 0xd4ec7f8f, 0x2f39c569, 0x846071b8,
	42	0x798aaccb, 0xd2d3181a, 0x25786dd6, 0x8e21d907, 0x73cb0474, 0xd892b0a5,
	43	0x23470a43, 0x881ebe92, 0x75f463e1, 0xdeadd730, 0x63f67950, 0xc8afcd81,
	44	0x354510f2, 0x9e1ca423, 0x65c91ec5, 0xce90aa14, 0x337a7767, 0x9823c3b6,
	45	0x6f88b67a, 0xc4d102ab, 0x393bdfd8, 0x92626b09, 0x69b7d1ef, 0xc2ee653e,
	46	0x3f04b84d, 0x945d0c9c, 0x7b0be704, 0xd05253d5, 0x2db88ea6, 0x86e13a77,
	47	0x7d348091, 0xd66d3440, 0x2b87e933, 0x80de5de2, 0x7775282e, 0xdc2c9cff,
	48	0x21c6418c, 0x8a9ff55d, 0x714a4fbb, 0xda13fb6a, 0x27f92619, 0x8ca092c8,
	49	0x520d45f8, 0xf954f129, 0x04be2c5a, 0xafe7988b, 0x5432226d, 0xff6b96bc,
	50	0x02814bcf, 0xa9d8ff1e, 0x5e738ad2, 0xf52a3e03, 0x08c0e370, 0xa39957a1,
	51	0x584ced47, 0xf3155996, 0x0eff84e5, 0xa5a63034, 0x4af0dbac, 0xe1a96f7d,
	52	0x1c43b20e, 0xb71a06df, 0x4ccfbc39, 0xe79608e8, 0x1a7cd59b, 0xb125614a,
	53	0x468e1486, 0xedd7a057, 0x103d7d24, 0xbb64c9f5, 0x40b17313, 0xebe8c7c2,
	54	0x16021ab1, 0xbd5bae60, 0x6cb54671, 0xc7ecf2a0, 0x3a062fd3, 0x915f9b02,
	55	0x6a8a21e4, 0xc1d39535, 0x3c394846, 0x9760fc97, 0x60cb895b, 0xcb923d8a,
	56	0x3678e0f9, 0x9d215428, 0x66f4eece, 0xcdad5a1f, 0x3047876c, 0x9b1e33bd,
	57	0x7448d825, 0xdf116cf4, 0x22fbb187, 0x89a20556, 0x7277bfb0, 0xd92e0b61,
	58	0x24c4d612, 0x8f9d62c3, 0x7836170f, 0xd36fa3de, 0x2e857ead, 0x85dcca7c,
	59	0x7e09709a, 0xd550c44b, 0x28ba1938, 0x83e3ade9, 0x5d4e7ad9, 0xf617ce08,
	60	0x0bfd137b, 0xa0a4a7aa, 0x5b711d4c, 0xf028a99d, 0x0dc274ee, 0xa69bc03f,
	61	0x5130b5f3, 0xfa690122, 0x0783dc51, 0xacda6880, 0x570fd266, 0xfc5666b7,
	62	0x01bcbbc4, 0xaae50f15, 0x45b3e48d, 0xeeea505c, 0x13008d2f, 0xb85939fe,
	63	0x438c8318, 0xe8d537c9, 0x153feaba, 0xbe665e6b, 0x49cd2ba7, 0xe2949f76,
	64	0x1f7e4205, 0xb427f6d4, 0x4ff24c32, 0xe4abf8e3, 0x19412590, 0xb2189141,
	65	0x0f433f21, 0xa41a8bf0, 0x59f05683, 0xf2a9e252, 0x097c58b4, 0xa225ec65,
	66	0x5fcf3116, 0xf49685c7, 0x033df00b, 0xa86444da, 0x558e99a9, 0xfed72d78,
	67	0x0502979e, 0xae5b234f, 0x53b1fe3c, 0xf8e84aed, 0x17bea175, 0xbce715a4,
	68	0x410dc8d7, 0xea547c06, 0x1181c6e0, 0xbad87231, 0x4732af42, 0xec6b1b93,
	69	0x1bc06e5f, 0xb099da8e, 0x4d7307fd, 0xe62ab32c, 0x1dff09ca, 0xb6a6bd1b,
	70	0x4b4c6068, 0xe015d4b9, 0x3eb80389, 0x95e1b758, 0x680b6a2b, 0xc352defa,
	71	0x3887641c, 0x93ded0cd, 0x6e340dbe, 0xc56db96f, 0x32c6cca3, 0x999f7872,
	72	0x6475a501, 0xcf2c11d0, 0x34f9ab36, 0x9fa01fe7, 0x624ac294, 0xc9137645,
	73	0x26459ddd, 0x8d1c290c, 0x70f6f47f, 0xdbaf40ae, 0x207afa48, 0x8b234e99,
	74	0x76c993ea, 0xdd90273b, 0x2a3b52f7, 0x8162e626, 0x7c883b55, 0xd7d18f84,
	75	0x2c043562, 0x875d81b3, 0x7ab75cc0, 0xd1eee811
	76	};
	77
	78	static const unsigned int U[256] = {
	79	0x00000000, 0x7eb5200d, 0x5633f4cb, 0x2886d4c6, 0x073e5d47, 0x798b7d4a,
	80	0x510da98c, 0x2fb88981, 0x0e7cba8e, 0x70c99a83, 0x584f4e45, 0x26fa6e48,
	81	0x0942e7c9, 0x77f7c7c4, 0x5f711302, 0x21c4330f, 0x1cf9751c, 0x624c5511,
	82	0x4aca81d7, 0x347fa1da, 0x1bc7285b, 0x65720856, 0x4df4dc90, 0x3341fc9d,
	83	0x1285cf92, 0x6c30ef9f, 0x44b63b59, 0x3a031b54, 0x15bb92d5, 0x6b0eb2d8,
	84	0x4388661e, 0x3d3d4613, 0x39f2ea38, 0x4747ca35, 0x6fc11ef3, 0x11743efe,
	85	0x3eccb77f, 0x40799772, 0x68ff43b4, 0x164a63b9, 0x378e50b6, 0x493b70bb,
	86	0x61bda47d, 0x1f088470, 0x30b00df1, 0x4e052dfc, 0x6683f93a, 0x1836d937,
	87	0x250b9f24, 0x5bbebf29, 0x73386bef, 0x0d8d4be2, 0x2235c263, 0x5c80e26e,
	88	0x740636a8, 0x0ab316a5, 0x2b7725aa, 0x55c205a7, 0x7d44d161, 0x03f1f16c,
	89	0x2c4978ed, 0x52fc58e0, 0x7a7a8c26, 0x04cfac2b, 0x73e5d470, 0x0d50f47d,
	90	0x25d620bb, 0x5b6300b6, 0x74db8937, 0x0a6ea93a, 0x22e87dfc, 0x5c5d5df1,
	91	0x7d996efe, 0x032c4ef3, 0x2baa9a35, 0x551fba38, 0x7aa733b9, 0x041213b4,
	92	0x2c94c772, 0x5221e77f, 0x6f1ca16c, 0x11a98161, 0x392f55a7, 0x479a75aa,
93	0x6822fc2b, 0x1697dc26, 0x3e1108e0, 0x40a428ed, 0x61601be2, 0x1fd53bef,
94	0x3753ef29, 0x49e6cf24, 0x665e46a5, 0x18eb66a8, 0x306db26e, 0x4ed89263,
95	0x4a173e48, 0x34a21e45, 0x1c24ca83, 0x6291ea8e, 0x4d29630f, 0x339c4302,
96	0x1b1a97c4, 0x65afb7c9, 0x446b84c6, 0x3adea4cb, 0x1258700d, 0x6ced5000,
97	0x4355d981, 0x3de0f98c, 0x15662d4a, 0x6bd30d47, 0x56ee4b54, 0x285b6b59,
98	0x00ddbf9f, 0x7e689f92, 0x51d01613, 0x2f65361e, 0x07e3e2d8, 0x7956c2d5,
99	0x5892f1da, 0x2627d1d7, 0x0ea10511, 0x7014251c, 0x5facac9d, 0x21198c90,
100	0x099f5856, 0x772a785b, 0x4c921c31, 0x32273c3c, 0x1aa1e8fa, 0x6414c8f7,
101	0x4bac4176, 0x3519617b, 0x1d9fb5bd, 0x632a95b0, 0x42eea6bf, 0x3c5b86b2,
102	0x14dd5274, 0x6a687279, 0x45d0fbf8, 0x3b65dbf5, 0x13e30f33, 0x6d562f3e,
103	0x506b692d, 0x2ede4920, 0x06589de6, 0x78edbdeb, 0x5755346a, 0x29e01467,
104	0x0166c0a1, 0x7fd3e0ac, 0x5e17d3a3, 0x20a2f3ae, 0x08242768, 0x76910765,
105	0x59298ee4, 0x279caee9, 0x0f1a7a2f, 0x71af5a22, 0x7560f609, 0x0bd5d604,
106	0x235302c2, 0x5de622cf, 0x725eab4e, 0x0ceb8b43, 0x246d5f85, 0x5ad87f88,
107	0x7b1c4c87, 0x05a96c8a, 0x2d2fb84c, 0x539a9841, 0x7c2211c0, 0x029731cd,
108	0x2a11e50b, 0x54a4c506, 0x69998315, 0x172ca318, 0x3faa77de, 0x411f57d3,
109	0x6ea7de52, 0x1012fe5f, 0x38942a99, 0x46210a94, 0x67e5399b, 0x19501996,
110	0x31d6cd50, 0x4f63ed5d, 0x60db64dc, 0x1e6e44d1, 0x36e89017, 0x485db01a,
111	0x3f77c841, 0x41c2e84c, 0x69443c8a, 0x17f11c87, 0x38499506, 0x46fcb50b,
112	0x6e7a61cd, 0x10cf41c0, 0x310b72cf, 0x4fbe52c2, 0x67388604, 0x198da609,
113	0x36352f88, 0x48800f85, 0x6006db43, 0x1eb3fb4e, 0x238ebd5d, 0x5d3b9d50,
114	0x75bd4996, 0x0b08699b, 0x24b0e01a, 0x5a05c017, 0x728314d1, 0x0c3634dc,
115	0x2df207d3, 0x534727de, 0x7bc1f318, 0x0574d315, 0x2acc5a94, 0x54797a99,
116	0x7cffae5f, 0x024a8e52, 0x06852279, 0x78300274, 0x50b6d6b2, 0x2e03f6bf,
117	0x01bb7f3e, 0x7f0e5f33, 0x57888bf5, 0x293dabf8, 0x08f998f7, 0x764cb8fa,
118	0x5eca6c3c, 0x207f4c31, 0x0fc7c5b0, 0x7172e5bd, 0x59f4317b, 0x27411176,
119	0x1a7c5765, 0x64c97768, 0x4c4fa3ae, 0x32fa83a3, 0x1d420a22, 0x63f72a2f,
120	0x4b71fee9, 0x35c4dee4, 0x1400edeb, 0x6ab5cde6, 0x42331920, 0x3c86392d,
121	0x133eb0ac, 0x6d8b90a1, 0x450d4467, 0x3bb8646a
122	};
a310d434	123
08abe669	124	struct index_entry {
a310d434	125	const unsigned char *ptr;
8e1454b5	126	unsigned int val;
08abe669	127	struct index_entry *next;
8e1454b5	128	};
a310d434	129
08abe669 NP	130	struct delta_index {
	131	const void *src_buf;
	132	unsigned long src_size;
3dc5a9e4	133	unsigned int hash_mask;
08abe669 NP	134	struct index_entry *hash[0];
	135	};
	136
	137	struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
a310d434	138	{
06a9f920	139	unsigned int i, hsize, hmask, entries, prev_val, *hash_count;
08abe669 NP	140	const unsigned char data, buffer = buf;
	141	struct delta_index *index;
	142	struct index_entry entry, *hash;
8e1454b5	143	void *mem;
06a9f920	144	unsigned long memsize;
8e1454b5	145
08abe669 NP	146	if (!buf \|\| !bufsize)
	147	return NULL;
	148
3dc5a9e4 NP	149	/* Determine index hash size. Note that indexing skips the
	150	first byte to allow for optimizing the rabin polynomial
	151	initialization in create_delta(). */
	152	entries = (bufsize - 1) / RABIN_WINDOW;
8e1454b5	153	hsize = entries / 4;
c13c6bf7	154	for (i = 4; (1 << i) < hsize && i < 31; i++);
8e1454b5	155	hsize = 1 << i;
3dc5a9e4	156	hmask = hsize - 1;
8e1454b5 NP	157
8e1454b5 NP	158	/* allocate lookup index */
06a9f920 NP	159	memsize = sizeof(*index) +
	160	sizeof(hash) hsize +
	161	sizeof(entry) entries;
	162	mem = malloc(memsize);
8e1454b5 NP	163	if (!mem)
8e1454b5 NP	164	return NULL;
08abe669 NP	165	index = mem;
08abe669 NP	166	mem = index + 1;
8e1454b5	167	hash = mem;
08abe669 NP	168	mem = hash + hsize;
	169	entry = mem;
	170
	171	index->src_buf = buf;
	172	index->src_size = bufsize;
3dc5a9e4	173	index->hash_mask = hmask;
8e1454b5 NP	174	memset(hash, 0, hsize * sizeof(*hash));
8e1454b5 NP	175
c13c6bf7 NP	176	/* allocate an array to count hash entries */
	177	hash_count = calloc(hsize, sizeof(*hash_count));
	178	if (!hash_count) {
08abe669	179	free(index);
c13c6bf7 NP	180	return NULL;
	181	}
	182
	183	/* then populate the index */
06a9f920 NP	184	prev_val = ~0;
	185	for (data = buffer + entries * RABIN_WINDOW - RABIN_WINDOW;
	186	data >= buffer;
	187	data -= RABIN_WINDOW) {
3dc5a9e4 NP	188	unsigned int val = 0;
	189	for (i = 1; i <= RABIN_WINDOW; i++)
	190	val = ((val << 8) \| data[i]) ^ T[val >> RABIN_SHIFT];
06a9f920 NP	191	if (val == prev_val) {
	192	/* keep the lowest of consecutive identical blocks */
	193	entry[-1].ptr = data + RABIN_WINDOW;
	194	} else {
	195	prev_val = val;
	196	i = val & hmask;
	197	entry->ptr = data + RABIN_WINDOW;
	198	entry->val = val;
	199	entry->next = hash[i];
	200	hash[i] = entry++;
	201	hash_count[i]++;
06a9f920	202	}
3dc5a9e4	203	}
a310d434	204
c13c6bf7 NP	205	/*
	206	* Determine a limit on the number of entries in the same hash
	207	* bucket. This guard us against patological data sets causing
	208	* really bad hash distribution with most entries in the same hash
	209	* bucket that would bring us to O(m*n) computing costs (m and n
	210	* corresponding to reference and target buffer sizes).
	211	*
08abe669	212	* Make sure none of the hash buckets has more entries than
c13c6bf7 NP	213	* we're willing to test. Otherwise we cull the entry list
	214	* uniformly to still preserve a good repartition across
	215	* the reference buffer.
	216	*/
	217	for (i = 0; i < hsize; i++) {
08abe669	218	if (hash_count[i] < HASH_LIMIT)
c13c6bf7 NP	219	continue;
	220	entry = hash[i];
	221	do {
08abe669 NP	222	struct index_entry *keep = entry;
08abe669 NP	223	int skip = hash_count[i] / HASH_LIMIT / 2;
c13c6bf7 NP	224	do {
	225	entry = entry->next;
	226	} while(--skip && entry);
	227	keep->next = entry;
	228	} while(entry);
	229	}
	230	free(hash_count);
	231
08abe669 NP	232	return index;
	233	}
	234
	235	void free_delta_index(struct delta_index *index)
	236	{
	237	free(index);
a310d434 NP	238	}
a310d434 NP	239
3dc5a9e4 NP	240	/*
	241	* The maximum size for any opcode sequence, including the initial header
	242	* plus rabin window plus biggest copy.
	243	*/
	244	#define MAX_OP_SIZE (5 + 5 + 1 + RABIN_WINDOW + 7)
fe474b58	245
08abe669 NP	246	void *
	247	create_delta(const struct delta_index *index,
	248	const void *trg_buf, unsigned long trg_size,
	249	unsigned long *delta_size, unsigned long max_size)
a310d434	250	{
2d08e5dd	251	unsigned int i, outpos, outsize, val;
5a1fb2ca	252	int inscnt;
8e1454b5 NP	253	const unsigned char ref_data, ref_top, data, top;
8e1454b5 NP	254	unsigned char *out;
a310d434	255
08abe669	256	if (!trg_buf \|\| !trg_size)
8e1454b5 NP	257	return NULL;
8e1454b5 NP	258
a310d434 NP	259	outpos = 0;
a310d434 NP	260	outsize = 8192;
fe474b58 NP	261	if (max_size && outsize >= max_size)
fe474b58 NP	262	outsize = max_size + MAX_OP_SIZE + 1;
a310d434	263	out = malloc(outsize);
08abe669	264	if (!out)
a310d434	265	return NULL;
a310d434 NP	266
a310d434 NP	267	/* store reference buffer size */
08abe669 NP	268	i = index->src_size;
	269	while (i >= 0x80) {
	270	out[outpos++] = i \| 0x80;
	271	i >>= 7;
69a2d426	272	}
08abe669	273	out[outpos++] = i;
a310d434 NP	274
a310d434 NP	275	/* store target buffer size */
08abe669 NP	276	i = trg_size;
	277	while (i >= 0x80) {
	278	out[outpos++] = i \| 0x80;
	279	i >>= 7;
69a2d426	280	}
08abe669	281	out[outpos++] = i;
a310d434	282
08abe669 NP	283	ref_data = index->src_buf;
	284	ref_top = ref_data + index->src_size;
	285	data = trg_buf;
	286	top = trg_buf + trg_size;
3dc5a9e4 NP	287
	288	outpos++;
	289	val = 0;
	290	for (i = 0; i < RABIN_WINDOW && data < top; i++, data++) {
	291	out[outpos++] = *data;
	292	val = ((val << 8) \| *data) ^ T[val >> RABIN_SHIFT];
	293	}
	294	inscnt = i;
a310d434	295
8e1454b5 NP	296	while (data < top) {
8e1454b5 NP	297	unsigned int moff = 0, msize = 0;
08abe669	298	struct index_entry *entry;
3dc5a9e4 NP	299	val ^= U[data[-RABIN_WINDOW]];
3dc5a9e4 NP	300	val = ((val << 8) \| *data) ^ T[val >> RABIN_SHIFT];
2d08e5dd	301	i = val & index->hash_mask;
08abe669 NP	302	for (entry = index->hash[i]; entry; entry = entry->next) {
	303	const unsigned char *ref = entry->ptr;
	304	const unsigned char *src = data;
	305	unsigned int ref_size = ref_top - ref;
	306	if (entry->val != val)
	307	continue;
	308	if (ref_size > top - src)
	309	ref_size = top - src;
	310	if (ref_size > 0x10000)
	311	ref_size = 0x10000;
	312	if (ref_size <= msize)
	313	break;
	314	while (ref_size-- && src++ == ref)
	315	ref++;
	316	if (msize < ref - entry->ptr) {
	317	/* this is our best match so far */
	318	msize = ref - entry->ptr;
	319	moff = entry->ptr - ref_data;
a310d434 NP	320	}
	321	}
	322
3dc5a9e4	323	if (msize < 4) {
a310d434 NP	324	if (!inscnt)
	325	outpos++;
	326	out[outpos++] = *data++;
	327	inscnt++;
	328	if (inscnt == 0x7f) {
	329	out[outpos - inscnt - 1] = inscnt;
	330	inscnt = 0;
	331	}
	332	} else {
8e1454b5 NP	333	unsigned char *op;
8e1454b5 NP	334
3dc5a9e4 NP	335	if (msize >= RABIN_WINDOW) {
	336	const unsigned char *sk;
	337	sk = data + msize - RABIN_WINDOW;
	338	val = 0;
	339	for (i = 0; i < RABIN_WINDOW; i++)
	340	val = ((val << 8) \| *sk++) ^ T[val >> RABIN_SHIFT];
	341	} else {
	342	const unsigned char *sk = data + 1;
	343	for (i = 1; i < msize; i++) {
	344	val ^= U[sk[-RABIN_WINDOW]];
	345	val = ((val << 8) \| *sk++) ^ T[val >> RABIN_SHIFT];
	346	}
	347	}
	348
a310d434	349	if (inscnt) {
5a1fb2ca NP	350	while (moff && ref_data[moff-1] == data[-1]) {
	351	if (msize == 0x10000)
	352	break;
	353	/* we can match one byte back */
	354	msize++;
	355	moff--;
	356	data--;
	357	outpos--;
	358	if (--inscnt)
	359	continue;
	360	outpos--; /* remove count slot */
	361	inscnt--; /* make it -1 */
	362	break;
	363	}
a310d434 NP	364	out[outpos - inscnt - 1] = inscnt;
	365	inscnt = 0;
	366	}
	367
	368	data += msize;
8e1454b5	369	op = out + outpos++;
a310d434 NP	370	i = 0x80;
	371
	372	if (moff & 0xff) { out[outpos++] = moff; i \|= 0x01; }
	373	moff >>= 8;
	374	if (moff & 0xff) { out[outpos++] = moff; i \|= 0x02; }
	375	moff >>= 8;
	376	if (moff & 0xff) { out[outpos++] = moff; i \|= 0x04; }
	377	moff >>= 8;
	378	if (moff & 0xff) { out[outpos++] = moff; i \|= 0x08; }
	379
	380	if (msize & 0xff) { out[outpos++] = msize; i \|= 0x10; }
	381	msize >>= 8;
	382	if (msize & 0xff) { out[outpos++] = msize; i \|= 0x20; }
	383
8e1454b5	384	*op = i;
a310d434 NP	385	}
a310d434 NP	386
fe474b58	387	if (outpos >= outsize - MAX_OP_SIZE) {
a310d434 NP	388	void *tmp = out;
a310d434 NP	389	outsize = outsize * 3 / 2;
fe474b58 NP	390	if (max_size && outsize >= max_size)
	391	outsize = max_size + MAX_OP_SIZE + 1;
	392	if (max_size && outpos > max_size)
3dc5a9e4 NP	393	break;
3dc5a9e4 NP	394	out = realloc(out, outsize);
a310d434 NP	395	if (!out) {
a310d434 NP	396	free(tmp);
a310d434 NP	397	return NULL;
	398	}
	399	}
	400	}
	401
	402	if (inscnt)
	403	out[outpos - inscnt - 1] = inscnt;
	404
3dc5a9e4 NP	405	if (max_size && outpos > max_size) {
	406	free(out);
	407	return NULL;
	408	}
	409
a310d434 NP	410	*delta_size = outpos;
	411	return out;
	412	}