xdiff/xhistogram.c

   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"
  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;
  56         } **records, /* an occurrence */
  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(xrecord_t *r1, xrecord_t *r2)
  92 {
  93         return r1->ha == r2->ha;
  94
  95 }
  96
  97 #define CMP(i, s1, l1, s2, l2) \
  98         (cmp_recs(REC(i->env, s1, l1), REC(i->env, s2, l2)))
  99
 100 #define TABLE_HASH(index, side, line) \
 101         XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
 102
 103 static int scanA(struct histindex *index, int line1, int count1)
 104 {
 105         unsigned int ptr, tbl_idx;
 106         unsigned int chain_len;
 107         struct record **rec_chain, *rec;
 108
 109         for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
 110                 tbl_idx = TABLE_HASH(index, 1, ptr);
 111                 rec_chain = index->records + tbl_idx;
 112                 rec = *rec_chain;
 113
 114                 chain_len = 0;
 115                 while (rec) {
 116                         if (CMP(index, 1, rec->ptr, 1, ptr)) {
 117                                 /*
 118                                  * ptr is identical to another element. Insert
 119                                  * it onto the front of the existing element
 120                                  * chain.
 121                                  */
 122                                 NEXT_PTR(index, ptr) = rec->ptr;
 123                                 rec->ptr = ptr;
 124                                 /* cap rec->cnt at MAX_CNT */
 125                                 rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
 126                                 LINE_MAP(index, ptr) = rec;
 127                                 goto continue_scan;
 128                         }
 129
 130                         rec = rec->next;
 131                         chain_len++;
 132                 }
 133
 134                 if (chain_len == index->max_chain_length)
 135                         return -1;
 136
 137                 /*
 138                  * This is the first time we have ever seen this particular
 139                  * element in the sequence. Construct a new chain for it.
 140                  */
 141                 if (!(rec = xdl_cha_alloc(&index->rcha)))
 142                         return -1;
 143                 rec->ptr = ptr;
 144                 rec->cnt = 1;
 145                 rec->next = *rec_chain;
 146                 *rec_chain = rec;
 147                 LINE_MAP(index, ptr) = rec;
 148
 149 continue_scan:
 150                 ; /* no op */
 151         }
 152
 153         return 0;
 154 }
 155
 156 static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
 157         int line1, int count1, int line2, int count2)
 158 {
 159         unsigned int b_next = b_ptr + 1;
 160         struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
 161         unsigned int as, ae, bs, be, np, rc;
 162         int should_break;
 163
 164         for (; rec; rec = rec->next) {
 165                 if (rec->cnt > index->cnt) {
 166                         if (!index->has_common)
 167                                 index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
 168                         continue;
 169                 }
 170
 171                 as = rec->ptr;
 172                 if (!CMP(index, 1, as, 2, b_ptr))
 173                         continue;
 174
 175                 index->has_common = 1;
 176                 for (;;) {
 177                         should_break = 0;
 178                         np = NEXT_PTR(index, as);
 179                         bs = b_ptr;
 180                         ae = as;
 181                         be = bs;
 182                         rc = rec->cnt;
 183
 184                         while (line1 < as && line2 < bs
 185                                 && CMP(index, 1, as - 1, 2, bs - 1)) {
 186                                 as--;
 187                                 bs--;
 188                                 if (1 < rc)
 189                                         rc = XDL_MIN(rc, CNT(index, as));
 190                         }
 191                         while (ae < LINE_END(1) && be < LINE_END(2)
 192                                 && CMP(index, 1, ae + 1, 2, be + 1)) {
 193                                 ae++;
 194                                 be++;
 195                                 if (1 < rc)
 196                                         rc = XDL_MIN(rc, CNT(index, ae));
 197                         }
 198
 199                         if (b_next <= be)
 200                                 b_next = be + 1;
 201                         if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
 202                                 lcs->begin1 = as;
 203                                 lcs->begin2 = bs;
 204                                 lcs->end1 = ae;
 205                                 lcs->end2 = be;
 206                                 index->cnt = rc;
 207                         }
 208
 209                         if (np == 0)
 210                                 break;
 211
 212                         while (np <= ae) {
 213                                 np = NEXT_PTR(index, np);
 214                                 if (np == 0) {
 215                                         should_break = 1;
 216                                         break;
 217                                 }
 218                         }
 219
 220                         if (should_break)
 221                                 break;
 222
 223                         as = np;
 224                 }
 225         }
 226         return b_next;
 227 }
 228
 229 static int fall_back_to_classic_diff(xpparam_t const *xpp, xdfenv_t *env,
 230                 int line1, int count1, int line2, int count2)
 231 {
 232         xpparam_t xpparam;
 233
 234         memset(&xpparam, 0, sizeof(xpparam));
 235         xpparam.flags = xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
 236
 237         return xdl_fall_back_diff(env, &xpparam,
 238                                   line1, count1, line2, count2);
 239 }
 240
 241 static inline void free_index(struct histindex *index)
 242 {
 243         xdl_free(index->records);
 244         xdl_free(index->line_map);
 245         xdl_free(index->next_ptrs);
 246         xdl_cha_free(&index->rcha);
 247 }
 248
 249 static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
 250                     struct region *lcs,
 251                     int line1, int count1, int line2, int count2)
 252 {
 253         int b_ptr;
 254         int ret = -1;
 255         struct histindex index;
 256
 257         memset(&index, 0, sizeof(index));
 258
 259         index.env = env;
 260         index.xpp = xpp;
 261
 262         index.records = NULL;
 263         index.line_map = NULL;
 264         /* in case of early xdl_cha_free() */
 265         index.rcha.head = NULL;
 266
 267         index.table_bits = xdl_hashbits(count1);
 268         index.records_size = 1 << index.table_bits;
 269         if (!XDL_CALLOC_ARRAY(index.records, index.records_size))
 270                 goto cleanup;
 271
 272         index.line_map_size = count1;
 273         if (!XDL_CALLOC_ARRAY(index.line_map, index.line_map_size))
 274                 goto cleanup;
 275
 276         if (!XDL_CALLOC_ARRAY(index.next_ptrs, index.line_map_size))
 277                 goto cleanup;
 278
 279         /* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
 280         if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
 281                 goto cleanup;
 282
 283         index.ptr_shift = line1;
 284         index.max_chain_length = 64;
 285
 286         if (scanA(&index, line1, count1))
 287                 goto cleanup;
 288
 289         index.cnt = index.max_chain_length + 1;
 290
 291         for (b_ptr = line2; b_ptr <= LINE_END(2); )
 292                 b_ptr = try_lcs(&index, lcs, b_ptr, line1, count1, line2, count2);
 293
 294         if (index.has_common && index.max_chain_length < index.cnt)
 295                 ret = 1;
 296         else
 297                 ret = 0;
 298
 299 cleanup:
 300         free_index(&index);
 301         return ret;
 302 }
 303
 304 static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
 305         int line1, int count1, int line2, int count2)
 306 {
 307         struct region lcs;
 308         int lcs_found;
 309         int result;
 310 redo:
 311         result = -1;
 312
 313         if (count1 <= 0 && count2 <= 0)
 314                 return 0;
 315
 316         if (LINE_END(1) >= MAX_PTR)
 317                 return -1;
 318
 319         if (!count1) {
 320                 while(count2--)
 321                         env->xdf2.rchg[line2++ - 1] = 1;
 322                 return 0;
 323         } else if (!count2) {
 324                 while(count1--)
 325                         env->xdf1.rchg[line1++ - 1] = 1;
 326                 return 0;
 327         }
 328
 329         memset(&lcs, 0, sizeof(lcs));
 330         lcs_found = find_lcs(xpp, env, &lcs, line1, count1, line2, count2);
 331         if (lcs_found < 0)
 332                 goto out;
 333         else if (lcs_found)
 334                 result = fall_back_to_classic_diff(xpp, env, line1, count1, line2, count2);
 335         else {
 336                 if (lcs.begin1 == 0 && lcs.begin2 == 0) {
 337                         while (count1--)
 338                                 env->xdf1.rchg[line1++ - 1] = 1;
 339                         while (count2--)
 340                                 env->xdf2.rchg[line2++ - 1] = 1;
 341                         result = 0;
 342                 } else {
 343                         result = histogram_diff(xpp, env,
 344                                                 line1, lcs.begin1 - line1,
 345                                                 line2, lcs.begin2 - line2);
 346                         if (result)
 347                                 goto out;
 348                         /*
 349                          * result = histogram_diff(xpp, env,
 350                          *            lcs.end1 + 1, LINE_END(1) - lcs.end1,
 351                          *            lcs.end2 + 1, LINE_END(2) - lcs.end2);
 352                          * but let's optimize tail recursion ourself:
 353                         */
 354                         count1 = LINE_END(1) - lcs.end1;
 355                         line1 = lcs.end1 + 1;
 356                         count2 = LINE_END(2) - lcs.end2;
 357                         line2 = lcs.end2 + 1;
 358                         goto redo;
 359                 }
 360         }
 361 out:
 362         return result;
 363 }
 364
 365 int xdl_do_histogram_diff(xpparam_t const *xpp, xdfenv_t *env)
 366 {
 367         return histogram_diff(xpp, env,
 368                 env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
 369                 env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
 370 }