teach --histogram to diff
Port JGit's HistogramDiff algorithm over to C. Rough numbers (TODO) show that it is faster than its --patience cousin, as well as the default Meyers algorithm. The implementation has been reworked to use structs and pointers, instead of bitmasks, thus doing away with JGit's 2^28 line limit. We also use xdiff's default hash table implementation (xdl_hash_bits() with XDL_HASHLONG()) for convenience. Signed-off-by: Tay Ray Chuan <rctay89@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>maint
Tay Ray Chuan
Junio C Hamano
parent
46c8f2988d
commit
8c912eea94
2
Makefile
2
Makefile
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@ -1838,7 +1838,7 @@ ifndef NO_CURL
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GIT_OBJS += http.o http-walker.o remote-curl.o
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endif
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XDIFF_OBJS = xdiff/xdiffi.o xdiff/xprepare.o xdiff/xutils.o xdiff/xemit.o \
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xdiff/xmerge.o xdiff/xpatience.o
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xdiff/xmerge.o xdiff/xpatience.o xdiff/xhistogram.o
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VCSSVN_OBJS = vcs-svn/string_pool.o vcs-svn/line_buffer.o \
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vcs-svn/repo_tree.o vcs-svn/fast_export.o vcs-svn/svndump.o
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VCSSVN_TEST_OBJS = test-obj-pool.o test-string-pool.o \
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2
diff.c
2
diff.c
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@ -3369,6 +3369,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
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DIFF_XDL_SET(options, IGNORE_WHITESPACE_AT_EOL);
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else if (!strcmp(arg, "--patience"))
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DIFF_XDL_SET(options, PATIENCE_DIFF);
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else if (!strcmp(arg, "--histogram"))
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DIFF_XDL_SET(options, HISTOGRAM_DIFF);
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/* flags options */
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else if (!strcmp(arg, "--binary")) {
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@ -1759,6 +1759,8 @@ int parse_merge_opt(struct merge_options *o, const char *s)
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o->subtree_shift = s + strlen("subtree=");
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else if (!strcmp(s, "patience"))
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o->xdl_opts |= XDF_PATIENCE_DIFF;
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else if (!strcmp(s, "histogram"))
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o->xdl_opts |= XDF_HISTOGRAM_DIFF;
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else if (!strcmp(s, "ignore-space-change"))
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o->xdl_opts |= XDF_IGNORE_WHITESPACE_CHANGE;
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else if (!strcmp(s, "ignore-all-space"))
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@ -0,0 +1,12 @@
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#!/bin/sh
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test_description='histogram diff algorithm'
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. ./test-lib.sh
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. "$TEST_DIRECTORY"/lib-diff-alternative.sh
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test_diff_frobnitz "histogram"
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test_diff_unique "histogram"
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test_done
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@ -33,6 +33,7 @@ extern "C" {
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#define XDF_IGNORE_WHITESPACE_CHANGE (1 << 3)
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#define XDF_IGNORE_WHITESPACE_AT_EOL (1 << 4)
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#define XDF_PATIENCE_DIFF (1 << 5)
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#define XDF_HISTOGRAM_DIFF (1 << 6)
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#define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | XDF_IGNORE_WHITESPACE_CHANGE | XDF_IGNORE_WHITESPACE_AT_EOL)
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#define XDL_PATCH_NORMAL '-'
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@ -331,6 +331,9 @@ int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
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if (xpp->flags & XDF_PATIENCE_DIFF)
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return xdl_do_patience_diff(mf1, mf2, xpp, xe);
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if (xpp->flags & XDF_HISTOGRAM_DIFF)
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return xdl_do_histogram_diff(mf1, mf2, xpp, xe);
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if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
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return -1;
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@ -57,5 +57,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
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xdemitconf_t const *xecfg);
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int xdl_do_patience_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
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xdfenv_t *env);
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int xdl_do_histogram_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
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xdfenv_t *env);
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#endif /* #if !defined(XDIFFI_H) */
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@ -0,0 +1,384 @@
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/*
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* Copyright (C) 2010, Google Inc.
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* and other copyright owners as documented in JGit's IP log.
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*
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* This program and the accompanying materials are made available
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* under the terms of the Eclipse Distribution License v1.0 which
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* accompanies this distribution, is reproduced below, and is
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* available at http://www.eclipse.org/org/documents/edl-v10.php
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* - Neither the name of the Eclipse Foundation, Inc. nor the
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* names of its contributors may be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "xinclude.h"
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#include "xtypes.h"
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#include "xdiff.h"
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#define MAX_PTR UINT_MAX
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#define MAX_CNT UINT_MAX
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#define LINE_END(n) (line##n + count##n - 1)
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#define LINE_END_PTR(n) (*line##n + *count##n - 1)
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struct histindex {
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struct record {
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unsigned int ptr, cnt;
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struct record *next;
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} **records, /* an ocurrence */
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**line_map; /* map of line to record chain */
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chastore_t rcha;
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unsigned int *next_ptrs;
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unsigned int table_bits,
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records_size,
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line_map_size;
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unsigned int max_chain_length,
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key_shift,
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ptr_shift;
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unsigned int cnt,
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has_common;
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xdfenv_t *env;
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xpparam_t const *xpp;
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};
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struct region {
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unsigned int begin1, end1;
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unsigned int begin2, end2;
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};
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#define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])
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#define NEXT_PTR(index, ptr) \
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(index->next_ptrs[(ptr) - index->ptr_shift])
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#define CNT(index, ptr) \
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((LINE_MAP(index, ptr))->cnt)
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#define REC(env, s, l) \
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(env->xdf##s.recs[l - 1])
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static int cmp_recs(xpparam_t const *xpp,
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xrecord_t *r1, xrecord_t *r2)
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{
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return r1->ha == r2->ha &&
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xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
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xpp->flags);
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}
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#define CMP_ENV(xpp, env, s1, l1, s2, l2) \
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(cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
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#define CMP(i, s1, l1, s2, l2) \
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(CMP_ENV(i->xpp, i->env, s1, l1, s2, l2))
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#define TABLE_HASH(index, side, line) \
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XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
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static int scanA(struct histindex *index, int line1, int count1)
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{
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unsigned int ptr, tbl_idx;
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unsigned int chain_len;
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struct record **rec_chain, *rec;
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for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
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tbl_idx = TABLE_HASH(index, 1, ptr);
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rec_chain = index->records + tbl_idx;
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rec = *rec_chain;
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chain_len = 0;
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while (rec) {
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if (CMP(index, 1, rec->ptr, 1, ptr)) {
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/*
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* ptr is identical to another element. Insert
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* it onto the front of the existing element
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* chain.
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*/
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NEXT_PTR(index, ptr) = rec->ptr;
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rec->ptr = ptr;
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/* cap rec->cnt at MAX_CNT */
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rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
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LINE_MAP(index, ptr) = rec;
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goto continue_scan;
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}
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rec = rec->next;
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chain_len++;
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}
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if (chain_len == index->max_chain_length)
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return -1;
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/*
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* This is the first time we have ever seen this particular
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* element in the sequence. Construct a new chain for it.
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*/
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if (!(rec = xdl_cha_alloc(&index->rcha)))
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return -1;
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rec->ptr = ptr;
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rec->cnt = 1;
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rec->next = *rec_chain;
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*rec_chain = rec;
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LINE_MAP(index, ptr) = rec;
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continue_scan:
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; /* no op */
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}
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return 0;
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}
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static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
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int line1, int count1, int line2, int count2)
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{
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unsigned int b_next = b_ptr + 1;
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struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
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unsigned int as, ae, bs, be, np, rc;
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int should_break;
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for (; rec; rec = rec->next) {
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if (rec->cnt > index->cnt) {
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if (!index->has_common)
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index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
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continue;
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}
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as = rec->ptr;
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if (!CMP(index, 1, as, 2, b_ptr))
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continue;
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index->has_common = 1;
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for (;;) {
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should_break = 0;
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np = NEXT_PTR(index, as);
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bs = b_ptr;
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ae = as;
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be = bs;
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rc = rec->cnt;
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while (line1 < as && line2 < bs
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&& CMP(index, 1, as - 1, 2, bs - 1)) {
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as--;
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bs--;
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if (1 < rc)
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rc = XDL_MIN(rc, CNT(index, as));
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}
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while (ae < LINE_END(1) && be < LINE_END(2)
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&& CMP(index, 1, ae + 1, 2, be + 1)) {
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ae++;
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be++;
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if (1 < rc)
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rc = XDL_MIN(rc, CNT(index, ae));
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}
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if (b_next <= be)
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b_next = be + 1;
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if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
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lcs->begin1 = as;
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lcs->begin2 = bs;
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lcs->end1 = ae;
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lcs->end2 = be;
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index->cnt = rc;
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}
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if (np == 0)
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break;
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while (np <= ae) {
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np = NEXT_PTR(index, np);
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if (np == 0) {
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should_break = 1;
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break;
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}
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}
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if (should_break)
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break;
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as = np;
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}
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}
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return b_next;
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}
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static int find_lcs(struct histindex *index, struct region *lcs,
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int line1, int count1, int line2, int count2) {
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int b_ptr;
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if (scanA(index, line1, count1))
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return -1;
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index->cnt = index->max_chain_length + 1;
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for (b_ptr = line2; b_ptr <= LINE_END(2); )
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b_ptr = try_lcs(index, lcs, b_ptr, line1, count1, line2, count2);
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return index->has_common && index->max_chain_length < index->cnt;
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}
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static void reduce_common_start_end(xpparam_t const *xpp, xdfenv_t *env,
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int *line1, int *count1, int *line2, int *count2)
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{
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if (*count1 <= 1 || *count2 <= 1)
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return;
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while (*count1 > 1 && *count2 > 1 && CMP_ENV(xpp, env, 1, *line1, 2, *line2)) {
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(*line1)++;
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(*count1)--;
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(*line2)++;
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(*count2)--;
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}
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while (*count1 > 1 && *count2 > 1 && CMP_ENV(xpp, env, 1, LINE_END_PTR(1), 2, LINE_END_PTR(2))) {
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(*count1)--;
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(*count2)--;
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}
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}
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static int fall_back_to_classic_diff(struct histindex *index,
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int line1, int count1, int line2, int count2)
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{
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xpparam_t xpp;
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xpp.flags = index->xpp->flags & ~XDF_HISTOGRAM_DIFF;
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return xdl_fall_back_diff(index->env, &xpp,
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line1, count1, line2, count2);
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}
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static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
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int line1, int count1, int line2, int count2)
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{
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struct histindex index;
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struct region lcs;
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int sz;
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int result = -1;
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if (count1 <= 0 && count2 <= 0)
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return 0;
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if (LINE_END(1) >= MAX_PTR)
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return -1;
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if (!count1) {
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while(count2--)
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env->xdf2.rchg[line2++ - 1] = 1;
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return 0;
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} else if (!count2) {
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while(count1--)
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env->xdf1.rchg[line1++ - 1] = 1;
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return 0;
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}
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memset(&index, 0, sizeof(index));
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index.env = env;
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index.xpp = xpp;
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index.records = NULL;
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index.line_map = NULL;
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/* in case of early xdl_cha_free() */
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index.rcha.head = NULL;
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|
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index.table_bits = xdl_hashbits(count1);
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sz = index.records_size = 1 << index.table_bits;
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sz *= sizeof(struct record *);
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if (!(index.records = (struct record **) xdl_malloc(sz)))
|
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goto cleanup;
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memset(index.records, 0, sz);
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|
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sz = index.line_map_size = count1;
|
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sz *= sizeof(struct record *);
|
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if (!(index.line_map = (struct record **) xdl_malloc(sz)))
|
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goto cleanup;
|
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memset(index.line_map, 0, sz);
|
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|
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sz = index.line_map_size;
|
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sz *= sizeof(unsigned int);
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if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
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goto cleanup;
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memset(index.next_ptrs, 0, sz);
|
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|
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/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
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if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
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goto cleanup;
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index.ptr_shift = line1;
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index.max_chain_length = 64;
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memset(&lcs, 0, sizeof(lcs));
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if (find_lcs(&index, &lcs, line1, count1, line2, count2))
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result = fall_back_to_classic_diff(&index, line1, count1, line2, count2);
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else {
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result = 0;
|
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if (lcs.begin1 == 0 && lcs.begin2 == 0) {
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int ptr;
|
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for (ptr = 0; ptr < count1; ptr++)
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env->xdf1.rchg[line1 + ptr - 1] = 1;
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for (ptr = 0; ptr < count2; ptr++)
|
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env->xdf2.rchg[line2 + ptr - 1] = 1;
|
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} else {
|
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result = histogram_diff(xpp, env,
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line1, lcs.begin1 - line1,
|
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line2, lcs.begin2 - line2);
|
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result = histogram_diff(xpp, env,
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lcs.end1 + 1, LINE_END(1) - lcs.end1,
|
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lcs.end2 + 1, LINE_END(2) - lcs.end2);
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result *= -1;
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}
|
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}
|
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|
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cleanup:
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xdl_free(index.records);
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xdl_free(index.line_map);
|
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xdl_free(index.next_ptrs);
|
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xdl_cha_free(&index.rcha);
|
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|
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return result;
|
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}
|
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|
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int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
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||||
xpparam_t const *xpp, xdfenv_t *env)
|
||||
{
|
||||
int line1, line2, count1, count2;
|
||||
|
||||
if (xdl_prepare_env(file1, file2, xpp, env) < 0)
|
||||
return -1;
|
||||
|
||||
line1 = line2 = 1;
|
||||
count1 = env->xdf1.nrec;
|
||||
count2 = env->xdf2.nrec;
|
||||
|
||||
reduce_common_start_end(xpp, env, &line1, &count1, &line2, &count2);
|
||||
|
||||
return histogram_diff(xpp, env, line1, count1, line2, count2);
|
||||
}
|
||||
Loading…
Reference in New Issue