36671
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1 /*
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2 * Copyright (C) 2010, Google Inc.
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3 * and other copyright owners as documented in JGit's IP log.
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4 *
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5 * This program and the accompanying materials are made available
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6 * under the terms of the Eclipse Distribution License v1.0 which
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7 * accompanies this distribution, is reproduced below, and is
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8 * available at http://www.eclipse.org/org/documents/edl-v10.php
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9 *
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10 * All rights reserved.
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11 *
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12 * Redistribution and use in source and binary forms, with or
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13 * without modification, are permitted provided that the following
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14 * conditions are met:
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15 *
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16 * - Redistributions of source code must retain the above copyright
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17 * notice, this list of conditions and the following disclaimer.
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18 *
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19 * - Redistributions in binary form must reproduce the above
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20 * copyright notice, this list of conditions and the following
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21 * disclaimer in the documentation and/or other materials provided
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22 * with the distribution.
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23 *
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24 * - Neither the name of the Eclipse Foundation, Inc. nor the
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25 * names of its contributors may be used to endorse or promote
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26 * products derived from this software without specific prior
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27 * written permission.
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28 *
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29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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42 */
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43
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44 #include "xinclude.h"
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45 #include "xtypes.h"
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46 #include "xdiff.h"
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47
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48 #define MAX_PTR UINT_MAX
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49 #define MAX_CNT UINT_MAX
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50
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51 #define LINE_END(n) (line##n + count##n - 1)
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52 #define LINE_END_PTR(n) (*line##n + *count##n - 1)
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53
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54 struct histindex {
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55 struct record {
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56 unsigned int ptr, cnt;
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57 struct record *next;
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58 } **records, /* an occurrence */
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59 **line_map; /* map of line to record chain */
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60 chastore_t rcha;
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61 unsigned int *next_ptrs;
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62 unsigned int table_bits,
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63 records_size,
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64 line_map_size;
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65
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66 unsigned int max_chain_length,
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67 key_shift,
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68 ptr_shift;
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69
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70 unsigned int cnt,
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71 has_common;
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72
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73 xdfenv_t *env;
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74 xpparam_t const *xpp;
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75 };
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76
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77 struct region {
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78 unsigned int begin1, end1;
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79 unsigned int begin2, end2;
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80 };
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81
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82 #define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])
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83
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84 #define NEXT_PTR(index, ptr) \
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85 (index->next_ptrs[(ptr) - index->ptr_shift])
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86
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87 #define CNT(index, ptr) \
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88 ((LINE_MAP(index, ptr))->cnt)
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89
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90 #define REC(env, s, l) \
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91 (env->xdf##s.recs[l - 1])
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92
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93 static int cmp_recs(xpparam_t const *xpp,
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94 xrecord_t *r1, xrecord_t *r2)
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95 {
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96 return r1->ha == r2->ha &&
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97 xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
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98 xpp->flags);
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99 }
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100
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101 #define CMP_ENV(xpp, env, s1, l1, s2, l2) \
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102 (cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
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103
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104 #define CMP(i, s1, l1, s2, l2) \
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105 (cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
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106
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107 #define TABLE_HASH(index, side, line) \
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108 XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
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109
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110 static int scanA(struct histindex *index, int line1, int count1)
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111 {
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112 unsigned int ptr, tbl_idx;
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113 unsigned int chain_len;
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114 struct record **rec_chain, *rec;
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115
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116 for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
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117 tbl_idx = TABLE_HASH(index, 1, ptr);
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118 rec_chain = index->records + tbl_idx;
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119 rec = *rec_chain;
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120
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121 chain_len = 0;
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122 while (rec) {
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123 if (CMP(index, 1, rec->ptr, 1, ptr)) {
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124 /*
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125 * ptr is identical to another element. Insert
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126 * it onto the front of the existing element
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127 * chain.
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128 */
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129 NEXT_PTR(index, ptr) = rec->ptr;
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130 rec->ptr = ptr;
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131 /* cap rec->cnt at MAX_CNT */
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132 rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
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133 LINE_MAP(index, ptr) = rec;
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134 goto continue_scan;
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135 }
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136
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137 rec = rec->next;
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138 chain_len++;
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139 }
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140
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141 if (chain_len == index->max_chain_length)
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142 return -1;
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143
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144 /*
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145 * This is the first time we have ever seen this particular
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146 * element in the sequence. Construct a new chain for it.
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147 */
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148 if (!(rec = xdl_cha_alloc(&index->rcha)))
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149 return -1;
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150 rec->ptr = ptr;
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151 rec->cnt = 1;
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152 rec->next = *rec_chain;
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153 *rec_chain = rec;
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154 LINE_MAP(index, ptr) = rec;
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155
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156 continue_scan:
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157 ; /* no op */
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158 }
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159
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160 return 0;
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161 }
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162
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163 static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
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164 int line1, int count1, int line2, int count2)
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165 {
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166 unsigned int b_next = b_ptr + 1;
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167 struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
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168 unsigned int as, ae, bs, be, np, rc;
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169 int should_break;
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170
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171 for (; rec; rec = rec->next) {
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172 if (rec->cnt > index->cnt) {
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173 if (!index->has_common)
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174 index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
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175 continue;
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176 }
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177
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178 as = rec->ptr;
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179 if (!CMP(index, 1, as, 2, b_ptr))
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180 continue;
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181
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182 index->has_common = 1;
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183 for (;;) {
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184 should_break = 0;
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185 np = NEXT_PTR(index, as);
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186 bs = b_ptr;
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187 ae = as;
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188 be = bs;
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189 rc = rec->cnt;
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190
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191 while (line1 < as && line2 < bs
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192 && CMP(index, 1, as - 1, 2, bs - 1)) {
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193 as--;
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194 bs--;
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195 if (1 < rc)
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196 rc = XDL_MIN(rc, CNT(index, as));
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197 }
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198 while (ae < LINE_END(1) && be < LINE_END(2)
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199 && CMP(index, 1, ae + 1, 2, be + 1)) {
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200 ae++;
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201 be++;
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202 if (1 < rc)
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203 rc = XDL_MIN(rc, CNT(index, ae));
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204 }
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205
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206 if (b_next <= be)
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207 b_next = be + 1;
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208 if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
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209 lcs->begin1 = as;
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210 lcs->begin2 = bs;
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211 lcs->end1 = ae;
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212 lcs->end2 = be;
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213 index->cnt = rc;
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214 }
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215
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216 if (np == 0)
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217 break;
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218
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219 while (np <= ae) {
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220 np = NEXT_PTR(index, np);
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221 if (np == 0) {
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222 should_break = 1;
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223 break;
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224 }
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225 }
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226
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227 if (should_break)
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228 break;
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229
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230 as = np;
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231 }
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232 }
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233 return b_next;
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234 }
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235
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236 static int find_lcs(struct histindex *index, struct region *lcs,
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237 int line1, int count1, int line2, int count2) {
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238 int b_ptr;
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239
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240 if (scanA(index, line1, count1))
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241 return -1;
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242
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243 index->cnt = index->max_chain_length + 1;
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244
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245 for (b_ptr = line2; b_ptr <= LINE_END(2); )
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246 b_ptr = try_lcs(index, lcs, b_ptr, line1, count1, line2, count2);
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247
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248 return index->has_common && index->max_chain_length < index->cnt;
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249 }
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250
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251 static int fall_back_to_classic_diff(struct histindex *index,
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252 int line1, int count1, int line2, int count2)
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253 {
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254 xpparam_t xpp;
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255 xpp.flags = index->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
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256
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257 return xdl_fall_back_diff(index->env, &xpp,
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258 line1, count1, line2, count2);
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259 }
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260
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261 static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
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262 int line1, int count1, int line2, int count2)
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263 {
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264 struct histindex index;
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265 struct region lcs;
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266 int sz;
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267 int result = -1;
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268
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269 if (count1 <= 0 && count2 <= 0)
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270 return 0;
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271
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272 if (LINE_END(1) >= MAX_PTR)
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273 return -1;
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274
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275 if (!count1) {
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276 while(count2--)
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277 env->xdf2.rchg[line2++ - 1] = 1;
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278 return 0;
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279 } else if (!count2) {
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280 while(count1--)
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281 env->xdf1.rchg[line1++ - 1] = 1;
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282 return 0;
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283 }
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284
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285 memset(&index, 0, sizeof(index));
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286
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287 index.env = env;
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288 index.xpp = xpp;
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289
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290 index.records = NULL;
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291 index.line_map = NULL;
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292 /* in case of early xdl_cha_free() */
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293 index.rcha.head = NULL;
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294
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295 index.table_bits = xdl_hashbits(count1);
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296 sz = index.records_size = 1 << index.table_bits;
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297 sz *= sizeof(struct record *);
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298 if (!(index.records = (struct record **) xdl_malloc(sz)))
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299 goto cleanup;
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300 memset(index.records, 0, sz);
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301
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302 sz = index.line_map_size = count1;
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303 sz *= sizeof(struct record *);
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304 if (!(index.line_map = (struct record **) xdl_malloc(sz)))
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305 goto cleanup;
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306 memset(index.line_map, 0, sz);
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307
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308 sz = index.line_map_size;
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309 sz *= sizeof(unsigned int);
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310 if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
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311 goto cleanup;
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312 memset(index.next_ptrs, 0, sz);
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313
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314 /* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
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315 if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
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316 goto cleanup;
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317
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318 index.ptr_shift = line1;
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319 index.max_chain_length = 64;
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320
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321 memset(&lcs, 0, sizeof(lcs));
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322 if (find_lcs(&index, &lcs, line1, count1, line2, count2))
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323 result = fall_back_to_classic_diff(&index, line1, count1, line2, count2);
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324 else {
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325 if (lcs.begin1 == 0 && lcs.begin2 == 0) {
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326 while (count1--)
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327 env->xdf1.rchg[line1++ - 1] = 1;
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328 while (count2--)
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329 env->xdf2.rchg[line2++ - 1] = 1;
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330 result = 0;
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331 } else {
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332 result = histogram_diff(xpp, env,
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333 line1, lcs.begin1 - line1,
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334 line2, lcs.begin2 - line2);
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335 if (result)
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336 goto cleanup;
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337 result = histogram_diff(xpp, env,
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338 lcs.end1 + 1, LINE_END(1) - lcs.end1,
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339 lcs.end2 + 1, LINE_END(2) - lcs.end2);
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340 if (result)
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341 goto cleanup;
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342 }
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343 }
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344
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345 cleanup:
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346 xdl_free(index.records);
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347 xdl_free(index.line_map);
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348 xdl_free(index.next_ptrs);
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349 xdl_cha_free(&index.rcha);
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350
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351 return result;
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352 }
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353
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354 int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
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355 xpparam_t const *xpp, xdfenv_t *env)
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356 {
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357 if (xdl_prepare_env(file1, file2, xpp, env) < 0)
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358 return -1;
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359
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360 return histogram_diff(xpp, env,
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361 env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
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362 env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
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363 }
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