Andrew's git - gitweb.git/blob - 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
  52struct 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
  75struct 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
  91static 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) \
 103        (cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
 104
 105#define TABLE_HASH(index, side, line) \
 106        XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
 107
 108static 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
 154continue_scan:
 155                ; /* no op */
 156        }
 157
 158        return 0;
 159}
 160
 161static 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
 234static 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
 244static 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
 252static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
 253                    struct region *lcs,
 254                    int line1, int count1, int line2, int count2)
 255{
 256        int b_ptr;
 257        int sz, ret = -1;
 258        struct histindex index;
 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
 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
 309cleanup:
 310        free_index(&index);
 311        return ret;
 312}
 313
 314static 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;
 319        int result;
 320redo:
 321        result = -1;
 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
 339        memset(&lcs, 0, sizeof(lcs));
 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)
 344                result = fall_back_to_classic_diff(xpp, env, line1, count1, line2, count2);
 345        else {
 346                if (lcs.begin1 == 0 && lcs.begin2 == 0) {
 347                        while (count1--)
 348                                env->xdf1.rchg[line1++ - 1] = 1;
 349                        while (count2--)
 350                                env->xdf2.rchg[line2++ - 1] = 1;
 351                        result = 0;
 352                } else {
 353                        result = histogram_diff(xpp, env,
 354                                                line1, lcs.begin1 - line1,
 355                                                line2, lcs.begin2 - line2);
 356                        if (result)
 357                                goto out;
 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;
 369                }
 370        }
 371out:
 372        return result;
 373}
 374
 375int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
 376        xpparam_t const *xpp, xdfenv_t *env)
 377{
 378        if (xdl_prepare_env(file1, file2, xpp, env) < 0)
 379                return -1;
 380
 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);
 384}