[thirdparty/git.git] / xdiff / xhistogram.c

/*
 * Copyright (C) 2010, Google Inc.
 * and other copyright owners as documented in JGit's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "xinclude.h"

#define MAX_PTR	UINT_MAX
#define MAX_CNT	UINT_MAX

#define LINE_END(n) (line##n + count##n - 1)
#define LINE_END_PTR(n) (*line##n + *count##n - 1)

struct histindex {
	struct record {
		unsigned int ptr, cnt;
		struct record *next;
	} **records, /* an occurrence */
	  **line_map; /* map of line to record chain */
	chastore_t rcha;
	unsigned int *next_ptrs;
	unsigned int table_bits,
		     records_size,
		     line_map_size;

	unsigned int max_chain_length,
		     key_shift,
		     ptr_shift;

	unsigned int cnt,
		     has_common;

	xdfenv_t *env;
	xpparam_t const *xpp;
};

struct region {
	unsigned int begin1, end1;
	unsigned int begin2, end2;
};

#define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])

#define NEXT_PTR(index, ptr) \
	(index->next_ptrs[(ptr) - index->ptr_shift])

#define CNT(index, ptr) \
	((LINE_MAP(index, ptr))->cnt)

#define REC(env, s, l) \
	(env->xdf##s.recs[l - 1])

static int cmp_recs(xpparam_t const *xpp,
	xrecord_t *r1, xrecord_t *r2)
{
	return r1->ha == r2->ha &&
		xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
			    xpp->flags);
}

#define CMP_ENV(xpp, env, s1, l1, s2, l2) \
	(cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))

#define CMP(i, s1, l1, s2, l2) \
	(cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))

#define TABLE_HASH(index, side, line) \
	XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)

static int scanA(struct histindex *index, int line1, int count1)
{
	unsigned int ptr, tbl_idx;
	unsigned int chain_len;
	struct record **rec_chain, *rec;

	for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
		tbl_idx = TABLE_HASH(index, 1, ptr);
		rec_chain = index->records + tbl_idx;
		rec = *rec_chain;

		chain_len = 0;
		while (rec) {
			if (CMP(index, 1, rec->ptr, 1, ptr)) {
				/*
				 * ptr is identical to another element. Insert
				 * it onto the front of the existing element
				 * chain.
				 */
				NEXT_PTR(index, ptr) = rec->ptr;
				rec->ptr = ptr;
				/* cap rec->cnt at MAX_CNT */
				rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
				LINE_MAP(index, ptr) = rec;
				goto continue_scan;
			}

			rec = rec->next;
			chain_len++;
		}

		if (chain_len == index->max_chain_length)
			return -1;

		/*
		 * This is the first time we have ever seen this particular
		 * element in the sequence. Construct a new chain for it.
		 */
		if (!(rec = xdl_cha_alloc(&index->rcha)))
			return -1;
		rec->ptr = ptr;
		rec->cnt = 1;
		rec->next = *rec_chain;
		*rec_chain = rec;
		LINE_MAP(index, ptr) = rec;

continue_scan:
		; /* no op */
	}

	return 0;
}

static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
	int line1, int count1, int line2, int count2)
{
	unsigned int b_next = b_ptr + 1;
	struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
	unsigned int as, ae, bs, be, np, rc;
	int should_break;

	for (; rec; rec = rec->next) {
		if (rec->cnt > index->cnt) {
			if (!index->has_common)
				index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
			continue;
		}

		as = rec->ptr;
		if (!CMP(index, 1, as, 2, b_ptr))
			continue;

		index->has_common = 1;
		for (;;) {
			should_break = 0;
			np = NEXT_PTR(index, as);
			bs = b_ptr;
			ae = as;
			be = bs;
			rc = rec->cnt;

			while (line1 < as && line2 < bs
				&& CMP(index, 1, as - 1, 2, bs - 1)) {
				as--;
				bs--;
				if (1 < rc)
					rc = XDL_MIN(rc, CNT(index, as));
			}
			while (ae < LINE_END(1) && be < LINE_END(2)
				&& CMP(index, 1, ae + 1, 2, be + 1)) {
				ae++;
				be++;
				if (1 < rc)
					rc = XDL_MIN(rc, CNT(index, ae));
			}

			if (b_next <= be)
				b_next = be + 1;
			if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
				lcs->begin1 = as;
				lcs->begin2 = bs;
				lcs->end1 = ae;
				lcs->end2 = be;
				index->cnt = rc;
			}

			if (np == 0)
				break;

			while (np <= ae) {
				np = NEXT_PTR(index, np);
				if (np == 0) {
					should_break = 1;
					break;
				}
			}

			if (should_break)
				break;

			as = np;
		}
	}
	return b_next;
}

static int fall_back_to_classic_diff(xpparam_t const *xpp, xdfenv_t *env,
		int line1, int count1, int line2, int count2)
{
	xpparam_t xpparam;
	xpparam.flags = xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;

	return xdl_fall_back_diff(env, &xpparam,
				  line1, count1, line2, count2);
}

static inline void free_index(struct histindex *index)
{
	xdl_free(index->records);
	xdl_free(index->line_map);
	xdl_free(index->next_ptrs);
	xdl_cha_free(&index->rcha);
}

static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
		    struct region *lcs,
		    int line1, int count1, int line2, int count2)
{
	int b_ptr;
	int sz, ret = -1;
	struct histindex index;

	memset(&index, 0, sizeof(index));

	index.env = env;
	index.xpp = xpp;

	index.records = NULL;
	index.line_map = NULL;
	/* in case of early xdl_cha_free() */
	index.rcha.head = NULL;

	index.table_bits = xdl_hashbits(count1);
	sz = index.records_size = 1 << index.table_bits;
	sz *= sizeof(struct record *);
	if (!(index.records = (struct record **) xdl_malloc(sz)))
		goto cleanup;
	memset(index.records, 0, sz);

	sz = index.line_map_size = count1;
	sz *= sizeof(struct record *);
	if (!(index.line_map = (struct record **) xdl_malloc(sz)))
		goto cleanup;
	memset(index.line_map, 0, sz);

	sz = index.line_map_size;
	sz *= sizeof(unsigned int);
	if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
		goto cleanup;
	memset(index.next_ptrs, 0, sz);

	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
	if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
		goto cleanup;

	index.ptr_shift = line1;
	index.max_chain_length = 64;

	if (scanA(&index, line1, count1))
		goto cleanup;

	index.cnt = index.max_chain_length + 1;

	for (b_ptr = line2; b_ptr <= LINE_END(2); )
		b_ptr = try_lcs(&index, lcs, b_ptr, line1, count1, line2, count2);

	if (index.has_common && index.max_chain_length < index.cnt)
		ret = 1;
	else
		ret = 0;

cleanup:
	free_index(&index);
	return ret;
}

static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
	int line1, int count1, int line2, int count2)
{
	struct region lcs;
	int lcs_found;
	int result;
redo:
	result = -1;

	if (count1 <= 0 && count2 <= 0)
		return 0;

	if (LINE_END(1) >= MAX_PTR)
		return -1;

	if (!count1) {
		while(count2--)
			env->xdf2.rchg[line2++ - 1] = 1;
		return 0;
	} else if (!count2) {
		while(count1--)
			env->xdf1.rchg[line1++ - 1] = 1;
		return 0;
	}

	memset(&lcs, 0, sizeof(lcs));
	lcs_found = find_lcs(xpp, env, &lcs, line1, count1, line2, count2);
	if (lcs_found < 0)
		goto out;
	else if (lcs_found)
		result = fall_back_to_classic_diff(xpp, env, line1, count1, line2, count2);
	else {
		if (lcs.begin1 == 0 && lcs.begin2 == 0) {
			while (count1--)
				env->xdf1.rchg[line1++ - 1] = 1;
			while (count2--)
				env->xdf2.rchg[line2++ - 1] = 1;
			result = 0;
		} else {
			result = histogram_diff(xpp, env,
						line1, lcs.begin1 - line1,
						line2, lcs.begin2 - line2);
			if (result)
				goto out;
			/*
			 * result = histogram_diff(xpp, env,
			 *            lcs.end1 + 1, LINE_END(1) - lcs.end1,
			 *            lcs.end2 + 1, LINE_END(2) - lcs.end2);
			 * but let's optimize tail recursion ourself:
			*/
			count1 = LINE_END(1) - lcs.end1;
			line1 = lcs.end1 + 1;
			count2 = LINE_END(2) - lcs.end2;
			line2 = lcs.end2 + 1;
			goto redo;
		}
	}
out:
	return result;
}

int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
	xpparam_t const *xpp, xdfenv_t *env)
{
	if (xdl_prepare_env(file1, file2, xpp, env) < 0)
		return -1;

	return histogram_diff(xpp, env,
		env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
		env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
}
Commit	Line	Data
8c912eea TRC	1	/*
	2	* Copyright (C) 2010, Google Inc.
	3	* and other copyright owners as documented in JGit's IP log.
	4	*
	5	* This program and the accompanying materials are made available
	6	* under the terms of the Eclipse Distribution License v1.0 which
	7	* accompanies this distribution, is reproduced below, and is
	8	* available at http://www.eclipse.org/org/documents/edl-v10.php
	9	*
	10	* All rights reserved.
	11	*
	12	* Redistribution and use in source and binary forms, with or
	13	* without modification, are permitted provided that the following
	14	* conditions are met:
	15	*
	16	* - Redistributions of source code must retain the above copyright
	17	* notice, this list of conditions and the following disclaimer.
	18	*
	19	* - Redistributions in binary form must reproduce the above
	20	* copyright notice, this list of conditions and the following
	21	* disclaimer in the documentation and/or other materials provided
	22	* with the distribution.
	23	*
	24	* - Neither the name of the Eclipse Foundation, Inc. nor the
	25	* names of its contributors may be used to endorse or promote
	26	* products derived from this software without specific prior
	27	* written permission.
	28	*
	29	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
	30	* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
	31	* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	32	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	33	* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
	34	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	35	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	36	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	37	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	38	* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
	39	* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	40	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
	41	* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	42	*/
	43
	44	#include "xinclude.h"
8c912eea TRC	45
	46	#define MAX_PTR UINT_MAX
	47	#define MAX_CNT UINT_MAX
	48
	49	#define LINE_END(n) (line##n + count##n - 1)
	50	#define LINE_END_PTR(n) (line##n + count##n - 1)
	51
	52	struct histindex {
	53	struct record {
	54	unsigned int ptr, cnt;
	55	struct record *next;
41ccfdd9	56	} *records, / an occurrence */
8c912eea TRC	57	*line_map; / map of line to record chain */
	58	chastore_t rcha;
	59	unsigned int *next_ptrs;
	60	unsigned int table_bits,
	61	records_size,
	62	line_map_size;
	63
	64	unsigned int max_chain_length,
	65	key_shift,
	66	ptr_shift;
	67
	68	unsigned int cnt,
	69	has_common;
	70
	71	xdfenv_t *env;
	72	xpparam_t const *xpp;
	73	};
	74
	75	struct region {
	76	unsigned int begin1, end1;
	77	unsigned int begin2, end2;
	78	};
	79
	80	#define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])
	81
	82	#define NEXT_PTR(index, ptr) \
	83	(index->next_ptrs[(ptr) - index->ptr_shift])
	84
	85	#define CNT(index, ptr) \
	86	((LINE_MAP(index, ptr))->cnt)
	87
	88	#define REC(env, s, l) \
	89	(env->xdf##s.recs[l - 1])
	90
	91	static int cmp_recs(xpparam_t const *xpp,
	92	xrecord_t r1, xrecord_t r2)
	93	{
	94	return r1->ha == r2->ha &&
	95	xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
	96	xpp->flags);
	97	}
	98
	99	#define CMP_ENV(xpp, env, s1, l1, s2, l2) \
	100	(cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
	101
	102	#define CMP(i, s1, l1, s2, l2) \
43ca7530	103	(cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
8c912eea TRC	104
	105	#define TABLE_HASH(index, side, line) \
	106	XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
	107
	108	static int scanA(struct histindex *index, int line1, int count1)
	109	{
	110	unsigned int ptr, tbl_idx;
	111	unsigned int chain_len;
	112	struct record *rec_chain, rec;
	113
	114	for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
	115	tbl_idx = TABLE_HASH(index, 1, ptr);
	116	rec_chain = index->records + tbl_idx;
	117	rec = *rec_chain;
	118
	119	chain_len = 0;
	120	while (rec) {
	121	if (CMP(index, 1, rec->ptr, 1, ptr)) {
	122	/*
	123	* ptr is identical to another element. Insert
	124	* it onto the front of the existing element
	125	* chain.
	126	*/
	127	NEXT_PTR(index, ptr) = rec->ptr;
	128	rec->ptr = ptr;
	129	/* cap rec->cnt at MAX_CNT */
	130	rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
	131	LINE_MAP(index, ptr) = rec;
	132	goto continue_scan;
	133	}
	134
	135	rec = rec->next;
	136	chain_len++;
	137	}
	138
	139	if (chain_len == index->max_chain_length)
	140	return -1;
	141
	142	/*
	143	* This is the first time we have ever seen this particular
	144	* element in the sequence. Construct a new chain for it.
	145	*/
	146	if (!(rec = xdl_cha_alloc(&index->rcha)))
	147	return -1;
	148	rec->ptr = ptr;
	149	rec->cnt = 1;
	150	rec->next = *rec_chain;
	151	*rec_chain = rec;
	152	LINE_MAP(index, ptr) = rec;
	153
	154	continue_scan:
	155	; /* no op */
	156	}
	157
	158	return 0;
	159	}
	160
	161	static int try_lcs(struct histindex index, struct region lcs, int b_ptr,
	162	int line1, int count1, int line2, int count2)
	163	{
	164	unsigned int b_next = b_ptr + 1;
	165	struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
	166	unsigned int as, ae, bs, be, np, rc;
	167	int should_break;
168
169	for (; rec; rec = rec->next) {
170	if (rec->cnt > index->cnt) {
171	if (!index->has_common)
172	index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
173	continue;
174	}
175
176	as = rec->ptr;
177	if (!CMP(index, 1, as, 2, b_ptr))
178	continue;
179
180	index->has_common = 1;
181	for (;;) {
182	should_break = 0;
183	np = NEXT_PTR(index, as);
184	bs = b_ptr;
185	ae = as;
186	be = bs;
187	rc = rec->cnt;
188
189	while (line1 < as && line2 < bs
190	&& CMP(index, 1, as - 1, 2, bs - 1)) {
191	as--;
192	bs--;
193	if (1 < rc)
194	rc = XDL_MIN(rc, CNT(index, as));
195	}
196	while (ae < LINE_END(1) && be < LINE_END(2)
197	&& CMP(index, 1, ae + 1, 2, be + 1)) {
198	ae++;
199	be++;
200	if (1 < rc)
201	rc = XDL_MIN(rc, CNT(index, ae));
202	}
203
204	if (b_next <= be)
205	b_next = be + 1;
206	if (lcs->end1 - lcs->begin1 < ae - as \|\| rc < index->cnt) {
207	lcs->begin1 = as;
208	lcs->begin2 = bs;
209	lcs->end1 = ae;
210	lcs->end2 = be;
211	index->cnt = rc;
212	}
213
214	if (np == 0)
215	break;
216
217	while (np <= ae) {
218	np = NEXT_PTR(index, np);
219	if (np == 0) {
220	should_break = 1;
221	break;
222	}
223	}
224
225	if (should_break)
226	break;
227
228	as = np;
229	}
230	}
231	return b_next;
232	}
233
28209850 SB	234	static int fall_back_to_classic_diff(xpparam_t const xpp, xdfenv_t env,
	235	int line1, int count1, int line2, int count2)
	236	{
	237	xpparam_t xpparam;
	238	xpparam.flags = xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
	239
	240	return xdl_fall_back_diff(env, &xpparam,
	241	line1, count1, line2, count2);
	242	}
	243
c671d4b5 SB	244	static inline void free_index(struct histindex *index)
	245	{
	246	xdl_free(index->records);
	247	xdl_free(index->line_map);
	248	xdl_free(index->next_ptrs);
	249	xdl_cha_free(&index->rcha);
	250	}
	251
64c4e8bc SB	252	static int find_lcs(xpparam_t const xpp, xdfenv_t env,
	253	struct region *lcs,
	254	int line1, int count1, int line2, int count2)
8c912eea	255	{
64c4e8bc SB	256	int b_ptr;
64c4e8bc SB	257	int sz, ret = -1;
8c912eea	258	struct histindex index;
8c912eea TRC	259
	260	memset(&index, 0, sizeof(index));
	261
	262	index.env = env;
	263	index.xpp = xpp;
	264
	265	index.records = NULL;
	266	index.line_map = NULL;
	267	/* in case of early xdl_cha_free() */
	268	index.rcha.head = NULL;
	269
	270	index.table_bits = xdl_hashbits(count1);
	271	sz = index.records_size = 1 << index.table_bits;
	272	sz = sizeof(struct record );
	273	if (!(index.records = (struct record **) xdl_malloc(sz)))
	274	goto cleanup;
	275	memset(index.records, 0, sz);
	276
	277	sz = index.line_map_size = count1;
	278	sz = sizeof(struct record );
	279	if (!(index.line_map = (struct record **) xdl_malloc(sz)))
	280	goto cleanup;
	281	memset(index.line_map, 0, sz);
	282
	283	sz = index.line_map_size;
	284	sz *= sizeof(unsigned int);
	285	if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
	286	goto cleanup;
	287	memset(index.next_ptrs, 0, sz);
	288
	289	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
	290	if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
	291	goto cleanup;
	292
	293	index.ptr_shift = line1;
	294	index.max_chain_length = 64;
	295
64c4e8bc SB	296	if (scanA(&index, line1, count1))
	297	goto cleanup;
	298
	299	index.cnt = index.max_chain_length + 1;
	300
	301	for (b_ptr = line2; b_ptr <= LINE_END(2); )
	302	b_ptr = try_lcs(&index, lcs, b_ptr, line1, count1, line2, count2);
	303
	304	if (index.has_common && index.max_chain_length < index.cnt)
	305	ret = 1;
	306	else
	307	ret = 0;
	308
	309	cleanup:
	310	free_index(&index);
	311	return ret;
	312	}
	313
	314	static int histogram_diff(xpparam_t const xpp, xdfenv_t env,
	315	int line1, int count1, int line2, int count2)
	316	{
	317	struct region lcs;
	318	int lcs_found;
79cb2ebb SB	319	int result;
	320	redo:
	321	result = -1;
64c4e8bc SB	322
	323	if (count1 <= 0 && count2 <= 0)
	324	return 0;
	325
	326	if (LINE_END(1) >= MAX_PTR)
	327	return -1;
	328
	329	if (!count1) {
	330	while(count2--)
	331	env->xdf2.rchg[line2++ - 1] = 1;
	332	return 0;
	333	} else if (!count2) {
	334	while(count1--)
	335	env->xdf1.rchg[line1++ - 1] = 1;
	336	return 0;
	337	}
	338
8c912eea	339	memset(&lcs, 0, sizeof(lcs));
64c4e8bc SB	340	lcs_found = find_lcs(xpp, env, &lcs, line1, count1, line2, count2);
	341	if (lcs_found < 0)
	342	goto out;
	343	else if (lcs_found)
28209850	344	result = fall_back_to_classic_diff(xpp, env, line1, count1, line2, count2);
8c912eea	345	else {
8c912eea	346	if (lcs.begin1 == 0 && lcs.begin2 == 0) {
6486a84c TRC	347	while (count1--)
	348	env->xdf1.rchg[line1++ - 1] = 1;
	349	while (count2--)
	350	env->xdf2.rchg[line2++ - 1] = 1;
19f7a9c5	351	result = 0;
8c912eea TRC	352	} else {
8c912eea TRC	353	result = histogram_diff(xpp, env,
19f7a9c5 TRC	354	line1, lcs.begin1 - line1,
	355	line2, lcs.begin2 - line2);
	356	if (result)
64c4e8bc	357	goto out;
79cb2ebb SB	358	/*
	359	* result = histogram_diff(xpp, env,
	360	* lcs.end1 + 1, LINE_END(1) - lcs.end1,
	361	* lcs.end2 + 1, LINE_END(2) - lcs.end2);
	362	* but let's optimize tail recursion ourself:
	363	*/
	364	count1 = LINE_END(1) - lcs.end1;
	365	line1 = lcs.end1 + 1;
	366	count2 = LINE_END(2) - lcs.end2;
	367	line2 = lcs.end2 + 1;
	368	goto redo;
8c912eea TRC	369	}
8c912eea TRC	370	}
64c4e8bc	371	out:
8c912eea TRC	372	return result;
	373	}
	374
	375	int xdl_do_histogram_diff(mmfile_t file1, mmfile_t file2,
	376	xpparam_t const xpp, xdfenv_t env)
	377	{
8c912eea TRC	378	if (xdl_prepare_env(file1, file2, xpp, env) < 0)
	379	return -1;
	380
43ca7530 TRC	381	return histogram_diff(xpp, env,
	382	env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
	383	env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
8c912eea	384	}