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#include "xtypes.h"
  46#include "xdiff.h"
  47
  48#define MAX_PTR UINT_MAX
  49#define MAX_CNT UINT_MAX
  50
  51#define LINE_END(n) (line##n + count##n - 1)
  52#define LINE_END_PTR(n) (*line##n + *count##n - 1)
  53
  54struct histindex {
  55        struct record {
  56                unsigned int ptr, cnt;
  57                struct record *next;
  58        } **records, /* an occurrence */
  59          **line_map; /* map of line to record chain */
  60        chastore_t rcha;
  61        unsigned int *next_ptrs;
  62        unsigned int table_bits,
  63                     records_size,
  64                     line_map_size;
  65
  66        unsigned int max_chain_length,
  67                     key_shift,
  68                     ptr_shift;
  69
  70        unsigned int cnt,
  71                     has_common;
  72
  73        xdfenv_t *env;
  74        xpparam_t const *xpp;
  75};
  76
  77struct region {
  78        unsigned int begin1, end1;
  79        unsigned int begin2, end2;
  80};
  81
  82#define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])
  83
  84#define NEXT_PTR(index, ptr) \
  85        (index->next_ptrs[(ptr) - index->ptr_shift])
  86
  87#define CNT(index, ptr) \
  88        ((LINE_MAP(index, ptr))->cnt)
  89
  90#define REC(env, s, l) \
  91        (env->xdf##s.recs[l - 1])
  92
  93static int cmp_recs(xpparam_t const *xpp,
  94        xrecord_t *r1, xrecord_t *r2)
  95{
  96        return r1->ha == r2->ha &&
  97                xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
  98                            xpp->flags);
  99}
 100
 101#define CMP_ENV(xpp, env, s1, l1, s2, l2) \
 102        (cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
 103
 104#define CMP(i, s1, l1, s2, l2) \
 105        (cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
 106
 107#define TABLE_HASH(index, side, line) \
 108        XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
 109
 110static int scanA(struct histindex *index, int line1, int count1)
 111{
 112        unsigned int ptr, tbl_idx;
 113        unsigned int chain_len;
 114        struct record **rec_chain, *rec;
 115
 116        for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
 117                tbl_idx = TABLE_HASH(index, 1, ptr);
 118                rec_chain = index->records + tbl_idx;
 119                rec = *rec_chain;
 120
 121                chain_len = 0;
 122                while (rec) {
 123                        if (CMP(index, 1, rec->ptr, 1, ptr)) {
 124                                /*
 125                                 * ptr is identical to another element. Insert
 126                                 * it onto the front of the existing element
 127                                 * chain.
 128                                 */
 129                                NEXT_PTR(index, ptr) = rec->ptr;
 130                                rec->ptr = ptr;
 131                                /* cap rec->cnt at MAX_CNT */
 132                                rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
 133                                LINE_MAP(index, ptr) = rec;
 134                                goto continue_scan;
 135                        }
 136
 137                        rec = rec->next;
 138                        chain_len++;
 139                }
 140
 141                if (chain_len == index->max_chain_length)
 142                        return -1;
 143
 144                /*
 145                 * This is the first time we have ever seen this particular
 146                 * element in the sequence. Construct a new chain for it.
 147                 */
 148                if (!(rec = xdl_cha_alloc(&index->rcha)))
 149                        return -1;
 150                rec->ptr = ptr;
 151                rec->cnt = 1;
 152                rec->next = *rec_chain;
 153                *rec_chain = rec;
 154                LINE_MAP(index, ptr) = rec;
 155
 156continue_scan:
 157                ; /* no op */
 158        }
 159
 160        return 0;
 161}
 162
 163static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
 164        int line1, int count1, int line2, int count2)
 165{
 166        unsigned int b_next = b_ptr + 1;
 167        struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
 168        unsigned int as, ae, bs, be, np, rc;
 169        int should_break;
 170
 171        for (; rec; rec = rec->next) {
 172                if (rec->cnt > index->cnt) {
 173                        if (!index->has_common)
 174                                index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
 175                        continue;
 176                }
 177
 178                as = rec->ptr;
 179                if (!CMP(index, 1, as, 2, b_ptr))
 180                        continue;
 181
 182                index->has_common = 1;
 183                for (;;) {
 184                        should_break = 0;
 185                        np = NEXT_PTR(index, as);
 186                        bs = b_ptr;
 187                        ae = as;
 188                        be = bs;
 189                        rc = rec->cnt;
 190
 191                        while (line1 < as && line2 < bs
 192                                && CMP(index, 1, as - 1, 2, bs - 1)) {
 193                                as--;
 194                                bs--;
 195                                if (1 < rc)
 196                                        rc = XDL_MIN(rc, CNT(index, as));
 197                        }
 198                        while (ae < LINE_END(1) && be < LINE_END(2)
 199                                && CMP(index, 1, ae + 1, 2, be + 1)) {
 200                                ae++;
 201                                be++;
 202                                if (1 < rc)
 203                                        rc = XDL_MIN(rc, CNT(index, ae));
 204                        }
 205
 206                        if (b_next <= be)
 207                                b_next = be + 1;
 208                        if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
 209                                lcs->begin1 = as;
 210                                lcs->begin2 = bs;
 211                                lcs->end1 = ae;
 212                                lcs->end2 = be;
 213                                index->cnt = rc;
 214                        }
 215
 216                        if (np == 0)
 217                                break;
 218
 219                        while (np <= ae) {
 220                                np = NEXT_PTR(index, np);
 221                                if (np == 0) {
 222                                        should_break = 1;
 223                                        break;
 224                                }
 225                        }
 226
 227                        if (should_break)
 228                                break;
 229
 230                        as = np;
 231                }
 232        }
 233        return b_next;
 234}
 235
 236static int fall_back_to_classic_diff(xpparam_t const *xpp, xdfenv_t *env,
 237                int line1, int count1, int line2, int count2)
 238{
 239        xpparam_t xpparam;
 240        xpparam.flags = xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
 241
 242        return xdl_fall_back_diff(env, &xpparam,
 243                                  line1, count1, line2, count2);
 244}
 245
 246static inline void free_index(struct histindex *index)
 247{
 248        xdl_free(index->records);
 249        xdl_free(index->line_map);
 250        xdl_free(index->next_ptrs);
 251        xdl_cha_free(&index->rcha);
 252}
 253
 254static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
 255                    struct region *lcs,
 256                    int line1, int count1, int line2, int count2)
 257{
 258        int b_ptr;
 259        int sz, ret = -1;
 260        struct histindex index;
 261
 262        memset(&index, 0, sizeof(index));
 263
 264        index.env = env;
 265        index.xpp = xpp;
 266
 267        index.records = NULL;
 268        index.line_map = NULL;
 269        /* in case of early xdl_cha_free() */
 270        index.rcha.head = NULL;
 271
 272        index.table_bits = xdl_hashbits(count1);
 273        sz = index.records_size = 1 << index.table_bits;
 274        sz *= sizeof(struct record *);
 275        if (!(index.records = (struct record **) xdl_malloc(sz)))
 276                goto cleanup;
 277        memset(index.records, 0, sz);
 278
 279        sz = index.line_map_size = count1;
 280        sz *= sizeof(struct record *);
 281        if (!(index.line_map = (struct record **) xdl_malloc(sz)))
 282                goto cleanup;
 283        memset(index.line_map, 0, sz);
 284
 285        sz = index.line_map_size;
 286        sz *= sizeof(unsigned int);
 287        if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
 288                goto cleanup;
 289        memset(index.next_ptrs, 0, sz);
 290
 291        /* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
 292        if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
 293                goto cleanup;
 294
 295        index.ptr_shift = line1;
 296        index.max_chain_length = 64;
 297
 298        if (scanA(&index, line1, count1))
 299                goto cleanup;
 300
 301        index.cnt = index.max_chain_length + 1;
 302
 303        for (b_ptr = line2; b_ptr <= LINE_END(2); )
 304                b_ptr = try_lcs(&index, lcs, b_ptr, line1, count1, line2, count2);
 305
 306        if (index.has_common && index.max_chain_length < index.cnt)
 307                ret = 1;
 308        else
 309                ret = 0;
 310
 311cleanup:
 312        free_index(&index);
 313        return ret;
 314}
 315
 316static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
 317        int line1, int count1, int line2, int count2)
 318{
 319        struct region lcs;
 320        int lcs_found;
 321        int result;
 322redo:
 323        result = -1;
 324
 325        if (count1 <= 0 && count2 <= 0)
 326                return 0;
 327
 328        if (LINE_END(1) >= MAX_PTR)
 329                return -1;
 330
 331        if (!count1) {
 332                while(count2--)
 333                        env->xdf2.rchg[line2++ - 1] = 1;
 334                return 0;
 335        } else if (!count2) {
 336                while(count1--)
 337                        env->xdf1.rchg[line1++ - 1] = 1;
 338                return 0;
 339        }
 340
 341        memset(&lcs, 0, sizeof(lcs));
 342        lcs_found = find_lcs(xpp, env, &lcs, line1, count1, line2, count2);
 343        if (lcs_found < 0)
 344                goto out;
 345        else if (lcs_found)
 346                result = fall_back_to_classic_diff(xpp, env, line1, count1, line2, count2);
 347        else {
 348                if (lcs.begin1 == 0 && lcs.begin2 == 0) {
 349                        while (count1--)
 350                                env->xdf1.rchg[line1++ - 1] = 1;
 351                        while (count2--)
 352                                env->xdf2.rchg[line2++ - 1] = 1;
 353                        result = 0;
 354                } else {
 355                        result = histogram_diff(xpp, env,
 356                                                line1, lcs.begin1 - line1,
 357                                                line2, lcs.begin2 - line2);
 358                        if (result)
 359                                goto out;
 360                        /*
 361                         * result = histogram_diff(xpp, env,
 362                         *            lcs.end1 + 1, LINE_END(1) - lcs.end1,
 363                         *            lcs.end2 + 1, LINE_END(2) - lcs.end2);
 364                         * but let's optimize tail recursion ourself:
 365                        */
 366                        count1 = LINE_END(1) - lcs.end1;
 367                        line1 = lcs.end1 + 1;
 368                        count2 = LINE_END(2) - lcs.end2;
 369                        line2 = lcs.end2 + 1;
 370                        goto redo;
 371                }
 372        }
 373out:
 374        return result;
 375}
 376
 377int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
 378        xpparam_t const *xpp, xdfenv_t *env)
 379{
 380        if (xdl_prepare_env(file1, file2, xpp, env) < 0)
 381                return -1;
 382
 383        return histogram_diff(xpp, env,
 384                env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
 385                env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
 386}