lib/diff3.c

   1 /*      $OpenBSD: diff3.c,v 1.41 2016/10/18 21:06:52 millert Exp $      */
   2
   3 /*
   4  * Copyright (C) Caldera International Inc.  2001-2002.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code and documentation must retain the above
  11  *    copyright notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed or owned by Caldera
  18  *      International, Inc.
  19  * 4. Neither the name of Caldera International, Inc. nor the names of other
  20  *    contributors may be used to endorse or promote products derived from
  21  *    this software without specific prior written permission.
  22  *
  23  * USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
  24  * INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
  25  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  26  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  27  * IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE FOR ANY DIRECT,
  28  * INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  29  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  30  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  32  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  33  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  34  * POSSIBILITY OF SUCH DAMAGE.
  35  */
  36 /*-
  37  * Copyright (c) 1991, 1993
  38  *      The Regents of the University of California.  All rights reserved.
  39  *
  40  * Redistribution and use in source and binary forms, with or without
  41  * modification, are permitted provided that the following conditions
  42  * are met:
  43  * 1. Redistributions of source code must retain the above copyright
  44  *    notice, this list of conditions and the following disclaimer.
  45  * 2. Redistributions in binary form must reproduce the above copyright
  46  *    notice, this list of conditions and the following disclaimer in the
  47  *    documentation and/or other materials provided with the distribution.
  48  * 3. Neither the name of the University nor the names of its contributors
  49  *    may be used to endorse or promote products derived from this software
  50  *    without specific prior written permission.
  51  *
  52  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  53  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  54  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  55  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  56  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  57  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  58  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  59  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  60  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  61  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  62  * SUCH DAMAGE.
  63  *
  64  *      @(#)diff3.c     8.1 (Berkeley) 6/6/93
  65  */
  66
  67 #include "got_compat.h"
  68
  69 #include <sys/stat.h>
  70 #include <sys/queue.h>
  71
  72 #include <ctype.h>
  73 #include <limits.h>
  74 #include <stdio.h>
  75 #include <stdarg.h>
  76 #include <stdlib.h>
  77 #include <string.h>
  78 #include <time.h>
  79 #include <unistd.h>
  80
  81 #include "got_error.h"
  82 #include "got_opentemp.h"
  83 #include "got_object.h"
  84 #include "got_diff.h"
  85
  86 #include "buf.h"
  87 #include "rcsutil.h"
  88 #include "got_lib_diff.h"
  89
  90 #ifndef nitems
  91 #define nitems(_a) (sizeof(_a) / sizeof((_a)[0]))
  92 #endif
  93
  94 /* diff3 - 3-way differential file comparison */
  95
  96 /* diff3 [-ex3EX] d13 d23 f1 f2 f3 [m1 m3]
  97  *
  98  * d13 = diff report on f1 vs f3
  99  * d23 = diff report on f2 vs f3
 100  * f1, f2, f3 the 3 files
 101  * if changes in f1 overlap with changes in f3, m1 and m3 are used
 102  * to mark the overlaps; otherwise, the file names f1 and f3 are used
 103  * (only for options E and X).
 104  */
 105
 106 /*
 107  * "from" is first in range of changed lines; "to" is last+1
 108  * from=to=line after point of insertion for added lines.
 109  */
 110 struct line_range {
 111         int from;
 112         int to;
 113 };
 114
 115 struct off_range {
 116         off_t from;
 117         off_t to;
 118 };
 119
 120 struct diff {
 121         struct line_range old;
 122         struct line_range new;
 123         struct off_range oldo;
 124         struct off_range newo;
 125 };
 126
 127 struct diff3_state {
 128         size_t szchanges;
 129
 130         struct diff *d13;
 131         struct diff *d23;
 132
 133         /*
 134          * "de" is used to gather editing scripts.  These are later spewed out
 135          * in reverse order.  Its first element must be all zero, the "new"
 136          * component of "de" contains line positions, and "oldo" and "newo"
 137          * components contain byte positions.
 138          * Array overlap indicates which sections in "de" correspond to lines
 139          * that are different in all three files.
 140          */
 141         struct diff *de;
 142         char *overlap;
 143         int overlapcnt;
 144         FILE *fp[3];
 145         int cline[3];           /* # of the last-read line in each file (0-2) */
 146
 147         /*
 148          * the latest known correspondence between line numbers of the 3 files
 149          * is stored in last[1-3];
 150          */
 151         int last[4];
 152         char f1mark[PATH_MAX];
 153         char f2mark[PATH_MAX];
 154         char f3mark[PATH_MAX];
 155
 156         char *buf;
 157
 158         BUF *diffbuf;
 159 };
 160
 161
 162 static const struct got_error *duplicate(int *, int, struct line_range *,
 163     struct line_range *, struct diff3_state *);
 164 static const struct got_error *edit(struct diff *, int, int *,
 165     struct diff3_state *);
 166 static const struct got_error *getchange(char **, FILE *, struct diff3_state *);
 167 static const struct got_error *get_line(char **, FILE *, size_t *,
 168     struct diff3_state *);
 169 static int number(char **);
 170 static const struct got_error *readin(size_t *, char *, struct diff **,
 171     struct diff3_state *);
 172 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
 173 static const struct got_error *skip(size_t *, int, int, struct diff3_state *);
 174 static const struct got_error *edscript(int, struct diff3_state *);
 175 static const struct got_error *merge(size_t, size_t, struct diff3_state *);
 176 static const struct got_error *prange(struct line_range *,
 177     struct diff3_state *);
 178 static const struct got_error *repos(int, struct diff3_state *);
 179 static const struct got_error *increase(struct diff3_state *);
 180 static const struct got_error *diff3_internal(char *, char *, char *,
 181     char *, char *, const char *, const char *, struct diff3_state *,
 182     const char *, const char *, const char *);
 183
 184 static const struct got_error *
 185 diff_output(BUF *diffbuf, const char *fmt, ...)
 186 {
 187         const struct got_error *err = NULL;
 188         va_list vap;
 189         int i;
 190         char *str;
 191         size_t newsize;
 192
 193         va_start(vap, fmt);
 194         i = vasprintf(&str, fmt, vap);
 195         va_end(vap);
 196         if (i == -1)
 197                 return got_error_from_errno("vasprintf");
 198         err = buf_append(&newsize, diffbuf, str, strlen(str));
 199         free(str);
 200         return err;
 201 }
 202
 203 static const struct got_error*
 204 diffreg(BUF **d, const char *path1, const char *path2,
 205     enum got_diff_algorithm diff_algo)
 206 {
 207         const struct got_error *err = NULL;
 208         FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
 209         char *outpath = NULL;
 210         struct got_diffreg_result *diffreg_result = NULL;
 211
 212         *d = NULL;
 213
 214         f1 = fopen(path1, "re");
 215         if (f1 == NULL) {
 216                 err = got_error_from_errno2("fopen", path1);
 217                 goto done;
 218         }
 219         f2 = fopen(path2, "re");
 220         if (f1 == NULL) {
 221                 err = got_error_from_errno2("fopen", path2);
 222                 goto done;
 223         }
 224
 225         err = got_opentemp_named(&outpath, &outfile,
 226             GOT_TMPDIR_STR "/got-diffreg", "");
 227         if (err)
 228                 goto done;
 229
 230         err = got_diffreg(&diffreg_result, f1, f2, diff_algo, 0, 0);
 231         if (err)
 232                 goto done;
 233
 234         if (diffreg_result) {
 235                 struct diff_result *diff_result = diffreg_result->result;
 236                 int atomizer_flags = (diff_result->left->atomizer_flags |
 237                     diff_result->right->atomizer_flags);
 238                 if ((atomizer_flags & DIFF_ATOMIZER_FOUND_BINARY_DATA)) {
 239                         err = got_error(GOT_ERR_FILE_BINARY);
 240                         goto done;
 241                 }
 242         }
 243
 244         err = got_diffreg_output(NULL, NULL, diffreg_result, 1, 1, "", "",
 245             GOT_DIFF_OUTPUT_PLAIN, 0, outfile);
 246         if (err)
 247                 goto done;
 248
 249         if (fflush(outfile) != 0) {
 250                 err = got_error_from_errno2("fflush", outpath);
 251                 goto done;
 252         }
 253         if (fseek(outfile, 0L, SEEK_SET) == -1) {
 254                 err = got_ferror(outfile, GOT_ERR_IO);
 255                 goto done;
 256         }
 257
 258         err = buf_load(d, outfile);
 259 done:
 260         if (outpath) {
 261                 if (unlink(outpath) == -1 && err == NULL)
 262                         err = got_error_from_errno2("unlink", outpath);
 263                 free(outpath);
 264         }
 265         if (outfile && fclose(outfile) == EOF && err == NULL)
 266                 err = got_error_from_errno("fclose");
 267         if (f1 && fclose(f1) == EOF && err == NULL)
 268                 err = got_error_from_errno("fclose");
 269         if (f2 && fclose(f2) == EOF && err == NULL)
 270                 err = got_error_from_errno("fclose");
 271         return err;
 272 }
 273
 274 /*
 275  * For merge(1).
 276  */
 277 const struct got_error *
 278 got_merge_diff3(int *overlapcnt, int outfd, FILE *f1, FILE *f2,
 279     FILE *f3, const char *label1, const char *label2, const char *label3,
 280     enum got_diff_algorithm diff_algo)
 281 {
 282         const struct got_error *err = NULL;
 283         char *dp13, *dp23, *path1, *path2, *path3;
 284         BUF *b1, *b2, *b3, *d1, *d2, *diffb;
 285         u_char *data, *patch;
 286         size_t dlen, plen, i;
 287         struct diff3_state *d3s;
 288
 289         *overlapcnt = 0;
 290
 291         d3s = calloc(1, sizeof(*d3s));
 292         if (d3s == NULL)
 293                 return got_error_from_errno("calloc");
 294
 295         b1 = b2 = b3 = d1 = d2 = diffb = NULL;
 296         dp13 = dp23 = path1 = path2 = path3 = NULL;
 297         data = patch = NULL;
 298
 299         err = buf_load(&b1, f1);
 300         if (err)
 301                 goto out;
 302         err = buf_load(&b2, f2);
 303         if (err)
 304                 goto out;
 305         err = buf_load(&b3, f3);
 306         if (err)
 307                 goto out;
 308
 309         err = buf_alloc(&diffb, 128);
 310         if (err)
 311                 goto out;
 312
 313         if (asprintf(&path1, GOT_TMPDIR_STR "/got-diff1.XXXXXXXX") == -1) {
 314                 err = got_error_from_errno("asprintf");
 315                 goto out;
 316         }
 317         if (asprintf(&path2, GOT_TMPDIR_STR "/got-diff2.XXXXXXXX") == -1) {
 318                 err = got_error_from_errno("asprintf");
 319                 goto out;
 320         }
 321         if (asprintf(&path3, GOT_TMPDIR_STR "/got-diff3.XXXXXXXX") == -1) {
 322                 err = got_error_from_errno("asprintf");
 323                 goto out;
 324         }
 325
 326         err = buf_write_stmp(b1, path1);
 327         if (err)
 328                 goto out;
 329         err = buf_write_stmp(b2, path2);
 330         if (err)
 331                 goto out;
 332         err = buf_write_stmp(b3, path3);
 333         if (err)
 334                 goto out;
 335
 336         buf_free(b2);
 337         b2 = NULL;
 338
 339         err = diffreg(&d1, path1, path3, diff_algo);
 340         if (err) {
 341                 buf_free(diffb);
 342                 diffb = NULL;
 343                 goto out;
 344
 345         }
 346         err = diffreg(&d2, path2, path3, diff_algo);
 347         if (err) {
 348                 buf_free(diffb);
 349                 diffb = NULL;
 350                 goto out;
 351         }
 352
 353         if (asprintf(&dp13, GOT_TMPDIR_STR "/got-d13.XXXXXXXXXX") == -1) {
 354                 err = got_error_from_errno("asprintf");
 355                 goto out;
 356         }
 357         err = buf_write_stmp(d1, dp13);
 358         if (err)
 359                 goto out;
 360
 361         buf_free(d1);
 362         d1 = NULL;
 363
 364         if (asprintf(&dp23, GOT_TMPDIR_STR "/got-d23.XXXXXXXXXX") == -1) {
 365                 err = got_error_from_errno("asprintf");
 366                 goto out;
 367         }
 368         err = buf_write_stmp(d2, dp23);
 369         if (err)
 370                 goto out;
 371
 372         buf_free(d2);
 373         d2 = NULL;
 374
 375         d3s->diffbuf = diffb;
 376         err = diff3_internal(dp13, dp23, path1, path2, path3,
 377             label1, label3, d3s, label1, label2, label3);
 378         if (err) {
 379                 buf_free(diffb);
 380                 diffb = NULL;
 381                 goto out;
 382         }
 383
 384         plen = buf_len(diffb);
 385         patch = buf_release(diffb);
 386         dlen = buf_len(b1);
 387         data = buf_release(b1);
 388
 389         diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
 390 out:
 391         buf_free(b2);
 392         buf_free(b3);
 393         buf_free(d1);
 394         buf_free(d2);
 395
 396         if (unlink(path1) == -1 && err == NULL)
 397                 err = got_error_from_errno2("unlink", path1);
 398         if (unlink(path2) == -1 && err == NULL)
 399                 err = got_error_from_errno2("unlink", path2);
 400         if (unlink(path3) == -1 && err == NULL)
 401                 err = got_error_from_errno2("unlink", path3);
 402         if (unlink(dp13) == -1 && err == NULL)
 403                 err = got_error_from_errno2("unlink", dp13);
 404         if (unlink(dp23) == -1 && err == NULL)
 405                 err = got_error_from_errno2("unlink", dp23);
 406
 407         free(path1);
 408         free(path2);
 409         free(path3);
 410         free(dp13);
 411         free(dp23);
 412         free(data);
 413         free(patch);
 414
 415         for (i = 0; i < nitems(d3s->fp); i++) {
 416                 if (d3s->fp[i] && fclose(d3s->fp[i]) == EOF && err == NULL)
 417                         err = got_error_from_errno("fclose");
 418         }
 419         if (err == NULL && diffb) {
 420                 if (buf_write_fd(diffb, outfd) < 0)
 421                         err = got_error_from_errno("buf_write_fd");
 422                 *overlapcnt = d3s->overlapcnt;
 423         }
 424         free(d3s);
 425         buf_free(diffb);
 426         return err;
 427 }
 428
 429 static const struct got_error *
 430 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
 431     const char *fmark, const char *rmark, struct diff3_state *d3s,
 432     const char *label1, const char *label2, const char *label3)
 433 {
 434         const struct got_error *err = NULL;
 435         ssize_t m, n;
 436         int i;
 437
 438         i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
 439             "%s%s%s", GOT_DIFF_CONFLICT_MARKER_BEGIN,
 440             label1 ? " " : "", label1 ? label1 : "");
 441         if (i < 0 || i >= (int)sizeof(d3s->f1mark))
 442                 return got_error(GOT_ERR_NO_SPACE);
 443
 444         i = snprintf(d3s->f2mark, sizeof(d3s->f2mark),
 445             "%s%s%s", GOT_DIFF_CONFLICT_MARKER_ORIG,
 446             label2 ? " " : "", label2 ? label2 : "");
 447         if (i < 0 || i >= (int)sizeof(d3s->f2mark))
 448                 return got_error(GOT_ERR_NO_SPACE);
 449
 450         i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
 451             "%s%s%s", GOT_DIFF_CONFLICT_MARKER_END,
 452             label3 ? " " : "", label3 ? label3 : "");
 453         if (i < 0 || i >= (int)sizeof(d3s->f3mark))
 454                 return got_error(GOT_ERR_NO_SPACE);
 455
 456         err = increase(d3s);
 457         if (err)
 458                 return err;
 459
 460         err = readin(&m, dp13, &d3s->d13, d3s);
 461         if (err)
 462                 return err;
 463         err = readin(&n, dp23, &d3s->d23, d3s);
 464         if (err)
 465                 return err;
 466
 467         if ((d3s->fp[0] = fopen(path1, "re")) == NULL)
 468                 return got_error_from_errno2("fopen", path1);
 469         if ((d3s->fp[1] = fopen(path2, "re")) == NULL)
 470                 return got_error_from_errno2("fopen", path2);
 471         if ((d3s->fp[2] = fopen(path3, "re")) == NULL)
 472                 return got_error_from_errno2("fopen", path3);
 473
 474         return merge(m, n, d3s);
 475 }
 476
 477 static int
 478 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
 479 {
 480         char op, *ep;
 481         struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
 482         int start, end, i, lineno;
 483         u_char tmp;
 484
 485         dlp = TAILQ_FIRST(&(dlines->l_lines));
 486         lp = TAILQ_FIRST(&(plines->l_lines));
 487
 488         end = 0;
 489         for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
 490             lp = TAILQ_NEXT(lp, l_list)) {
 491                 /* Skip blank lines */
 492                 if (lp->l_len < 2)
 493                         continue;
 494
 495                 /* NUL-terminate line buffer for strtol() safety. */
 496                 tmp = lp->l_line[lp->l_len - 1];
 497                 lp->l_line[lp->l_len - 1] = '\0';
 498
 499                 /* len - 1 is NUL terminator so we use len - 2 for 'op' */
 500                 op = lp->l_line[lp->l_len - 2];
 501                 start = (int)strtol(lp->l_line, &ep, 10);
 502
 503                 /* Restore the last byte of the buffer */
 504                 lp->l_line[lp->l_len - 1] = tmp;
 505
 506                 if (op == 'a') {
 507                         if (start > dlines->l_nblines ||
 508                             start < 0 || *ep != 'a')
 509                                 return -1;
 510                 } else if (op == 'c') {
 511                         if (start > dlines->l_nblines ||
 512                             start < 0 || (*ep != ',' && *ep != 'c'))
 513                                 return -1;
 514
 515                         if (*ep == ',') {
 516                                 ep++;
 517                                 end = (int)strtol(ep, &ep, 10);
 518                                 if (end < 0 || *ep != 'c')
 519                                         return -1;
 520                         } else {
 521                                 end = start;
 522                         }
 523                 }
 524
 525
 526                 for (;;) {
 527                         if (dlp == NULL)
 528                                 break;
 529                         if (dlp->l_lineno == start)
 530                                 break;
 531                         if (dlp->l_lineno > start) {
 532                                 dlp = TAILQ_PREV(dlp, tqh, l_list);
 533                         } else if (dlp->l_lineno < start) {
 534                                 ndlp = TAILQ_NEXT(dlp, l_list);
 535                                 if (ndlp->l_lineno > start)
 536                                         break;
 537                                 dlp = ndlp;
 538                         }
 539                 }
 540
 541                 if (dlp == NULL)
 542                         return -1;
 543
 544
 545                 if (op == 'c') {
 546                         insert_after = TAILQ_PREV(dlp, tqh, l_list);
 547                         for (i = 0; i <= (end - start); i++) {
 548                                 ndlp = TAILQ_NEXT(dlp, l_list);
 549                                 TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
 550                                 dlp = ndlp;
 551                         }
 552                         dlp = insert_after;
 553                 }
 554
 555                 if (op == 'a' || op == 'c') {
 556                         for (;;) {
 557                                 ndlp = lp;
 558                                 lp = TAILQ_NEXT(lp, l_list);
 559                                 if (lp == NULL)
 560                                         return -1;
 561
 562                                 if (lp->l_len == 2 &&
 563                                     lp->l_line[0] == '.' &&
 564                                     lp->l_line[1] == '\n')
 565                                         break;
 566
 567                                 if (lp->l_line[0] == ':') {
 568                                         lp->l_line++;
 569                                         lp->l_len--;
 570                                 }
 571                                 TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
 572                                 TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
 573                                     lp, l_list);
 574                                 dlp = lp;
 575
 576                                 lp->l_lineno = start;
 577                                 lp = ndlp;
 578                         }
 579                 }
 580
 581                 /*
 582                  * always resort lines as the markers might be put at the
 583                  * same line as we first started editing.
 584                  */
 585                 lineno = 0;
 586                 TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
 587                         sort->l_lineno = lineno++;
 588                 dlines->l_nblines = lineno - 1;
 589         }
 590
 591         return (0);
 592 }
 593
 594 /*
 595  * Pick up the line numbers of all changes from one change file.
 596  * (This puts the numbers in a vector, which is not strictly necessary,
 597  * since the vector is processed in one sequential pass.
 598  * The vector could be optimized out of existence)
 599  */
 600 static const struct got_error *
 601 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
 602 {
 603         const struct got_error *err = NULL;
 604         FILE *f;
 605         int a, b, c, d;
 606         char kind, *p;
 607         size_t i = 0;
 608
 609         *n = 0;
 610
 611         f = fopen(name, "re");
 612         if (f == NULL)
 613                 return got_error_from_errno2("fopen", name);
 614         err = getchange(&p, f, d3s);
 615         if (err)
 616                 goto done;
 617         for (i = 0; p; i++) {
 618                 if (i >= d3s->szchanges - 1) {
 619                         err = increase(d3s);
 620                         if (err)
 621                                 goto done;
 622                 }
 623                 a = b = number(&p);
 624                 if (*p == ',') {
 625                         p++;
 626                         b = number(&p);
 627                 }
 628                 kind = *p++;
 629                 c = d = number(&p);
 630                 if (*p == ',') {
 631                         p++;
 632                         d = number(&p);
 633                 }
 634                 if (kind == 'a')
 635                         a++;
 636                 if (kind == 'd')
 637                         c++;
 638                 b++;
 639                 d++;
 640                 (*dd)[i].old.from = a;
 641                 (*dd)[i].old.to = b;
 642                 (*dd)[i].new.from = c;
 643                 (*dd)[i].new.to = d;
 644
 645                 err = getchange(&p, f, d3s);
 646                 if (err)
 647                         goto done;
 648         }
 649
 650         if (i) {
 651                 (*dd)[i].old.from = (*dd)[i - 1].old.to;
 652                 (*dd)[i].new.from = (*dd)[i - 1].new.to;
 653         }
 654 done:
 655         if (fclose(f) == EOF && err == NULL)
 656                 err = got_error_from_errno("fclose");
 657         if (err == NULL)
 658                 *n = i;
 659         return err;
 660 }
 661
 662 static int
 663 number(char **lc)
 664 {
 665         int nn;
 666
 667         nn = 0;
 668         while (isdigit((unsigned char)(**lc)))
 669                 nn = nn*10 + *(*lc)++ - '0';
 670
 671         return (nn);
 672 }
 673
 674 static const struct got_error *
 675 getchange(char **line, FILE *b, struct diff3_state *d3s)
 676 {
 677         const struct got_error *err = NULL;
 678
 679         *line = NULL;
 680         do {
 681                 if (*line && isdigit((unsigned char)(*line)[0]))
 682                         return NULL;
 683                 err = get_line(line, b, NULL, d3s);
 684                 if (err)
 685                         return err;
 686         } while (*line);
 687
 688         return NULL;
 689 }
 690
 691 static const struct got_error *
 692 get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
 693 {
 694         const struct got_error *err = NULL;
 695         char *cp = NULL;
 696         size_t size = 0;
 697         ssize_t len;
 698         char *new;
 699
 700         *ret = NULL;
 701         if (n != NULL)
 702                 *n = 0;
 703
 704         len = getline(&cp, &size, b);
 705         if (len == -1) {
 706                 if (ferror(b))
 707                         err = got_error_from_errno("getline");
 708                 goto done;
 709         }
 710
 711         if (cp[len - 1] != '\n') {
 712                 len++;
 713                 if (len + 1 > size) {
 714                         new = realloc(cp, len + 1);
 715                         if (new == NULL) {
 716                                 err = got_error_from_errno("realloc");
 717                                 goto done;
 718                         }
 719                         cp = new;
 720                 }
 721                 cp[len - 1] = '\n';
 722                 cp[len] = '\0';
 723         }
 724
 725         free(d3s->buf);
 726         *ret = d3s->buf = cp;
 727         cp = NULL;
 728         if (n != NULL)
 729                 *n = len;
 730 done:
 731         free(cp);
 732         return err;
 733 }
 734
 735 static const struct got_error *
 736 merge(size_t m1, size_t m2, struct diff3_state *d3s)
 737 {
 738         const struct got_error *err = NULL;
 739         struct diff *d1, *d2;
 740         int dpl, j, t1, t2;
 741
 742         d1 = d3s->d13;
 743         d2 = d3s->d23;
 744         j = 0;
 745         for (;;) {
 746                 t1 = (d1 < d3s->d13 + m1);
 747                 t2 = (d2 < d3s->d23 + m2);
 748                 if (!t1 && !t2)
 749                         break;
 750
 751                 /* first file is different from others */
 752                 if (!t2 || (t1 && d1->new.to < d2->new.from)) {
 753                         /* stuff peculiar to 1st file */
 754                         d1++;
 755                         continue;
 756                 }
 757
 758                 /* second file is different from others */
 759                 if (!t1 || (t2 && d2->new.to < d1->new.from)) {
 760                         d2++;
 761                         continue;
 762                 }
 763
 764                 /*
 765                  * Merge overlapping changes in first file
 766                  * this happens after extension (see below).
 767                  */
 768                 if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
 769                         d1[1].old.from = d1->old.from;
 770                         d1[1].new.from = d1->new.from;
 771                         d1++;
 772                         continue;
 773                 }
 774
 775                 /* merge overlapping changes in second */
 776                 if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
 777                         d2[1].old.from = d2->old.from;
 778                         d2[1].new.from = d2->new.from;
 779                         d2++;
 780                         continue;
 781                 }
 782                 /* stuff peculiar to third file or different in all */
 783                 if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
 784                         err = duplicate(&dpl, j, &d1->old, &d2->old, d3s);
 785                         if (err)
 786                                 return err;
 787
 788                         /*
 789                          * dpl = 0 means all files differ
 790                          * dpl = 1 means files 1 and 2 identical
 791                          */
 792                         err = edit(d1, dpl, &j, d3s);
 793                         if (err)
 794                                 return err;
 795                         d1++;
 796                         d2++;
 797                         continue;
 798                 }
 799
 800                 /*
 801                  * Overlapping changes from file 1 and 2; extend changes
 802                  * appropriately to make them coincide.
 803                  */
 804                 if (d1->new.from < d2->new.from) {
 805                         d2->old.from -= d2->new.from - d1->new.from;
 806                         d2->new.from = d1->new.from;
 807                 } else if (d2->new.from < d1->new.from) {
 808                         d1->old.from -= d1->new.from - d2->new.from;
 809                         d1->new.from = d2->new.from;
 810                 }
 811                 if (d1->new.to > d2->new.to) {
 812                         d2->old.to += d1->new.to - d2->new.to;
 813                         d2->new.to = d1->new.to;
 814                 } else if (d2->new.to > d1->new.to) {
 815                         d1->old.to += d2->new.to - d1->new.to;
 816                         d1->new.to = d2->new.to;
 817                 }
 818         }
 819
 820         return (edscript(j, d3s));
 821 }
 822
 823 /*
 824  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
 825  */
 826 static const struct got_error *
 827 prange(struct line_range *rold, struct diff3_state *d3s)
 828 {
 829         const struct got_error *err = NULL;
 830
 831         if (rold->to <= rold->from) {
 832                 err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
 833                 if (err)
 834                         return err;
 835         } else {
 836                 err = diff_output(d3s->diffbuf, "%d", rold->from);
 837                 if (err)
 838                         return err;
 839                 if (rold->to > rold->from + 1) {
 840                         err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
 841                         if (err)
 842                                 return err;
 843                 }
 844                 err = diff_output(d3s->diffbuf, "c\n");
 845                 if (err)
 846                         return err;
 847         }
 848
 849         return NULL;
 850 }
 851
 852 /*
 853  * Skip to just before line number from in file "i".
 854  * Return the number of bytes skipped in *nskipped.
 855  */
 856 static const struct got_error *
 857 skip(size_t *nskipped, int i, int from, struct diff3_state *d3s)
 858 {
 859         const struct got_error *err = NULL;
 860         size_t len, n;
 861         char *line;
 862
 863         *nskipped = 0;
 864         for (n = 0; d3s->cline[i] < from - 1; n += len) {
 865                 err = get_line(&line, d3s->fp[i], &len, d3s);
 866                 if (err)
 867                         return err;
 868                 d3s->cline[i]++;
 869         }
 870         *nskipped = n;
 871         return NULL;
 872 }
 873
 874 /*
 875  * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
 876  * the same data as the new range (in file 2).
 877  *
 878  * If this change could overlap, remember start/end offsets in file 2 so we
 879  * can write out the original lines of text if a merge conflict occurs.
 880  */
 881 static const struct got_error *
 882 duplicate(int *dpl, int j, struct line_range *r1, struct line_range *r2,
 883     struct diff3_state *d3s)
 884 {
 885         const struct got_error *err = NULL;
 886         int c,d;
 887         int nchar;
 888         int nline;
 889         size_t nskipped;
 890         off_t off;
 891
 892         *dpl = 0;
 893
 894         if (r1->to - r1->from != r2->to - r2->from)
 895                 return NULL;
 896
 897         err = skip(&nskipped, 0, r1->from, d3s);
 898         if (err)
 899                 return err;
 900         err = skip(&nskipped, 1, r2->from, d3s);
 901         if (err)
 902                 return err;
 903
 904         off = ftello(d3s->fp[1]);
 905         if (off == -1)
 906                 return got_error_from_errno("ftello");
 907         d3s->de[j + 1].oldo.from = off; /* original lines start here */
 908
 909         nchar = 0;
 910         for (nline = 0; nline < r1->to - r1->from; nline++) {
 911                 do {
 912                         c = getc(d3s->fp[0]);
 913                         d = getc(d3s->fp[1]);
 914                         if (c == EOF && d == EOF)
 915                                 break;
 916                         else if (c == EOF)
 917                                 return got_ferror(d3s->fp[0], GOT_ERR_EOF);
 918                         else if (d == EOF)
 919                                 return got_ferror(d3s->fp[1], GOT_ERR_EOF);
 920                         nchar++;
 921                         if (c != d) {
 922                                 long orig_line_len = nchar;
 923                                 while (d != '\n') {
 924                                         d = getc(d3s->fp[1]);
 925                                         if (d == EOF)
 926                                                 break;
 927                                         orig_line_len++;
 928                                 }
 929                                 if (orig_line_len > nchar &&
 930                                     fseek(d3s->fp[1], -(orig_line_len - nchar),
 931                                     SEEK_CUR) == -1)
 932                                         return got_ferror(d3s->fp[1],
 933                                                 GOT_ERR_IO);
 934                                 /* original lines end here */
 935                                 d3s->de[j + 1].oldo.to = off + orig_line_len;
 936                                 err = repos(nchar, d3s);
 937                                 if (err)
 938                                         return err;
 939                                 return NULL;
 940                         }
 941                 } while (c != '\n');
 942         }
 943
 944         /* original lines end here */
 945         d3s->de[j + 1].oldo.to = off + nchar;
 946
 947         err = repos(nchar, d3s);
 948         if (err)
 949                 return err;
 950         *dpl = 1;
 951         return NULL;
 952 }
 953
 954 static const struct got_error *
 955 repos(int nchar, struct diff3_state *d3s)
 956 {
 957         int i;
 958
 959         for (i = 0; i < 2; i++) {
 960                 if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
 961                         return got_ferror(d3s->fp[i], GOT_ERR_IO);
 962         }
 963
 964         return NULL;
 965 }
 966
 967 /*
 968  * collect an editing script for later regurgitation
 969  */
 970 static const struct got_error *
 971 edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
 972 {
 973         const struct got_error *err = NULL;
 974         size_t nskipped;
 975
 976         if (((fdup + 1) & 3) == 0)
 977                 return NULL;
 978         (*j)++;
 979         d3s->overlap[*j] = !fdup;
 980         if (!fdup)
 981                 d3s->overlapcnt++;
 982         d3s->de[*j].old.from = diff->old.from;
 983         d3s->de[*j].old.to = diff->old.to;
 984
 985         err = skip(&nskipped, 2, diff->new.from, d3s);
 986         if (err)
 987                 return err;
 988         d3s->de[*j].newo.from = d3s->de[*j - 1].newo.to + nskipped;
 989
 990         err = skip(&nskipped, 2, diff->new.to, d3s);
 991         if (err)
 992                 return err;
 993         d3s->de[*j].newo.to = d3s->de[*j].newo.from + nskipped;
 994         return NULL;
 995 }
 996
 997 /* regurgitate */
 998 static const struct got_error *
 999 edscript(int n, struct diff3_state *d3s)
1000 {
1001         const struct got_error *err = NULL;
1002         off_t len;
1003         char *line = NULL;
1004         size_t linesize = 0;
1005         ssize_t linelen = 0, k;
1006
1007         for (; n > 0; n--) {
1008                 if (!d3s->overlap[n]) {
1009                         err = prange(&d3s->de[n].old, d3s);
1010                         if (err)
1011                                 return err;
1012                 } else if (d3s->de[n].oldo.from < d3s->de[n].oldo.to) {
1013                         /* Output a block of 3-way diff base file content. */
1014                         err = diff_output(d3s->diffbuf, "%da\n:%s\n",
1015                             d3s->de[n].old.to - 1, d3s->f2mark);
1016                         if (err)
1017                                 return err;
1018                         if (fseeko(d3s->fp[1], d3s->de[n].oldo.from, SEEK_SET)
1019                             == -1)
1020                                 return got_error_from_errno("fseeko");
1021                         len = (d3s->de[n].oldo.to - d3s->de[n].oldo.from);
1022                         for (k = 0; k < (ssize_t)len; k += linelen) {
1023                                 linelen = getline(&line, &linesize, d3s->fp[1]);
1024                                 if (linelen == -1) {
1025                                         if (feof(d3s->fp[1]))
1026                                                 break;
1027                                         err = got_ferror(d3s->fp[1],
1028                                             GOT_ERR_IO);
1029                                         goto done;
1030                                 }
1031                                 err = diff_output(d3s->diffbuf, ":%s", line);
1032                                 if (err)
1033                                         goto done;
1034                         }
1035                         err = diff_output(d3s->diffbuf, "%s%s\n",
1036                             linelen > 0 && line[linelen] == '\n' ? ":" : "",
1037                             GOT_DIFF_CONFLICT_MARKER_SEP);
1038                         if (err)
1039                                 goto done;
1040                 } else {
1041                         err = diff_output(d3s->diffbuf, "%da\n:%s\n",
1042                             d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
1043                         if (err)
1044                                 goto done;
1045                 }
1046                 if (fseeko(d3s->fp[2], d3s->de[n].newo.from, SEEK_SET)
1047                     == -1) {
1048                         err = got_error_from_errno("fseek");
1049                         goto done;
1050                 }
1051                 len = (d3s->de[n].newo.to - d3s->de[n].newo.from);
1052                 for (k = 0; k < (ssize_t)len; k += linelen) {
1053                         linelen = getline(&line, &linesize, d3s->fp[2]);
1054                         if (linelen == -1) {
1055                                 if (feof(d3s->fp[2]))
1056                                         break;
1057                                 err = got_ferror(d3s->fp[2], GOT_ERR_IO);
1058                                 goto done;
1059                         }
1060                         err = diff_output(d3s->diffbuf, ":%s", line);
1061                         if (err)
1062                                 goto done;
1063                 }
1064
1065                 if (!d3s->overlap[n]) {
1066                         err = diff_output(d3s->diffbuf, ".\n");
1067                         if (err)
1068                                 goto done;
1069                 } else {
1070                         err = diff_output(d3s->diffbuf, "%s%s\n.\n",
1071                             linelen > 0 && line[linelen] == '\n' ? ":" : "",
1072                             d3s->f3mark);
1073                         if (err)
1074                                 goto done;
1075                         err = diff_output(d3s->diffbuf, "%da\n:%s\n.\n",
1076                             d3s->de[n].old.from - 1, d3s->f1mark);
1077                         if (err)
1078                                 goto done;
1079                 }
1080         }
1081 done:
1082         free(line);
1083         return err;
1084 }
1085
1086 static const struct got_error *
1087 increase(struct diff3_state *d3s)
1088 {
1089         size_t newsz, incr;
1090         struct diff *d;
1091         char *s;
1092
1093         /* are the memset(3) calls needed? */
1094         newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
1095         incr = newsz - d3s->szchanges;
1096
1097         d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
1098         if (d == NULL)
1099                 return got_error_from_errno("reallocarray");
1100         d3s->d13 = d;
1101         memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
1102
1103         d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
1104         if (d == NULL)
1105                 return got_error_from_errno("reallocarray");
1106         d3s->d23 = d;
1107         memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
1108
1109         d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
1110         if (d == NULL)
1111                 return got_error_from_errno("reallocarray");
1112         d3s->de = d;
1113         memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
1114
1115         s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
1116         if (s == NULL)
1117                 return got_error_from_errno("reallocarray");
1118         d3s->overlap = s;
1119         memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1120         d3s->szchanges = newsz;
1121
1122         return NULL;
1123 }