text: /*
   * 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"
  #include "xtypes.h"
  #include "xdiff.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, unsigned int line1, unsigned int count1)
  {
  	unsigned int ptr;
  	unsigned int 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, unsigned int b_ptr,
  	unsigned int line1, unsigned int count1,
  	unsigned int line2, unsigned 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 find_lcs(
  	struct histindex *index, struct region *lcs,
  	unsigned int line1, unsigned int count1,
  	unsigned int line2, unsigned int count2)
  {
  	unsigned int b_ptr;
  
  	if (scanA(index, line1, count1))
  		return -1;
  
  	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);
  
  	return index->has_common && index->max_chain_length < index->cnt;
  }
  
  static int fall_back_to_classic_diff_xhistogram(struct histindex *index, //oz
  		int line1, int count1, int line2, int count2)
  {
  	xpparam_t xpp;
  	xpp.flags = index->xpp->flags & ~XDF_HISTOGRAM_DIFF;
  
  	return xdl_fall_back_diff(index->env, &xpp,
  				  line1, count1, line2, count2);
  }
  
  static int histogram_diff(
  	xpparam_t const *xpp, xdfenv_t *env,
  	unsigned int line1, unsigned int count1,
  	unsigned int line2, unsigned int count2)
  {
  	struct histindex index;
  	struct region lcs;
  	unsigned int sz;
  	int 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(&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;
  
  	memset(&lcs, 0, sizeof(lcs));
  	if (find_lcs(&index, &lcs, line1, count1, line2, count2))
  		result = fall_back_to_classic_diff_xhistogram(&index, line1, count1, line2, count2); //oz
  	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 cleanup;
  			result = histogram_diff(xpp, env,
  						lcs.end1 + 1, LINE_END(1) - lcs.end1,
  						lcs.end2 + 1, LINE_END(2) - lcs.end2);
  			if (result)
  				goto cleanup;
  		}
  	}
  
  cleanup:
  	xdl_free(index.records);
  	xdl_free(index.line_map);
  	xdl_free(index.next_ptrs);
  	xdl_cha_free(&index.rcha);
  
  	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);
  }
  