7b21a6b2cffa22b633fdc9cede6824e1da8367bd
   1/*
   2 *  LibXDiff by Davide Libenzi ( File Differential Library )
   3 *  Copyright (C) 2003-2006 Davide Libenzi, Johannes E. Schindelin
   4 *
   5 *  This library is free software; you can redistribute it and/or
   6 *  modify it under the terms of the GNU Lesser General Public
   7 *  License as published by the Free Software Foundation; either
   8 *  version 2.1 of the License, or (at your option) any later version.
   9 *
  10 *  This library is distributed in the hope that it will be useful,
  11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 *  Lesser General Public License for more details.
  14 *
  15 *  You should have received a copy of the GNU Lesser General Public
  16 *  License along with this library; if not, write to the Free Software
  17 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18 *
  19 *  Davide Libenzi <davidel@xmailserver.org>
  20 *
  21 */
  22
  23#include "xinclude.h"
  24
  25typedef struct s_xdmerge {
  26        struct s_xdmerge *next;
  27        /*
  28         * 0 = conflict,
  29         * 1 = no conflict, take first,
  30         * 2 = no conflict, take second.
  31         * 3 = no conflict, take both.
  32         */
  33        int mode;
  34        /*
  35         * These point at the respective postimages.  E.g. <i1,chg1> is
  36         * how side #1 wants to change the common ancestor; if there is no
  37         * overlap, lines before i1 in the postimage of side #1 appear
  38         * in the merge result as a region touched by neither side.
  39         */
  40        long i1, i2;
  41        long chg1, chg2;
  42        /*
  43         * These point at the preimage; of course there is just one
  44         * preimage, that is from the shared common ancestor.
  45         */
  46        long i0;
  47        long chg0;
  48} xdmerge_t;
  49
  50static int xdl_append_merge(xdmerge_t **merge, int mode,
  51                            long i0, long chg0,
  52                            long i1, long chg1,
  53                            long i2, long chg2)
  54{
  55        xdmerge_t *m = *merge;
  56        if (m && (i1 <= m->i1 + m->chg1 || i2 <= m->i2 + m->chg2)) {
  57                if (mode != m->mode)
  58                        m->mode = 0;
  59                m->chg0 = i0 + chg0 - m->i0;
  60                m->chg1 = i1 + chg1 - m->i1;
  61                m->chg2 = i2 + chg2 - m->i2;
  62        } else {
  63                m = xdl_malloc(sizeof(xdmerge_t));
  64                if (!m)
  65                        return -1;
  66                m->next = NULL;
  67                m->mode = mode;
  68                m->i0 = i0;
  69                m->chg0 = chg0;
  70                m->i1 = i1;
  71                m->chg1 = chg1;
  72                m->i2 = i2;
  73                m->chg2 = chg2;
  74                if (*merge)
  75                        (*merge)->next = m;
  76                *merge = m;
  77        }
  78        return 0;
  79}
  80
  81static int xdl_cleanup_merge(xdmerge_t *c)
  82{
  83        int count = 0;
  84        xdmerge_t *next_c;
  85
  86        /* were there conflicts? */
  87        for (; c; c = next_c) {
  88                if (c->mode == 0)
  89                        count++;
  90                next_c = c->next;
  91                free(c);
  92        }
  93        return count;
  94}
  95
  96static int xdl_merge_cmp_lines(xdfenv_t *xe1, int i1, xdfenv_t *xe2, int i2,
  97                int line_count, long flags)
  98{
  99        int i;
 100        xrecord_t **rec1 = xe1->xdf2.recs + i1;
 101        xrecord_t **rec2 = xe2->xdf2.recs + i2;
 102
 103        for (i = 0; i < line_count; i++) {
 104                int result = xdl_recmatch(rec1[i]->ptr, rec1[i]->size,
 105                        rec2[i]->ptr, rec2[i]->size, flags);
 106                if (!result)
 107                        return -1;
 108        }
 109        return 0;
 110}
 111
 112static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int add_nl, char *dest)
 113{
 114        xrecord_t **recs;
 115        int size = 0;
 116
 117        recs = (use_orig ? xe->xdf1.recs : xe->xdf2.recs) + i;
 118
 119        if (count < 1)
 120                return 0;
 121
 122        for (i = 0; i < count; size += recs[i++]->size)
 123                if (dest)
 124                        memcpy(dest + size, recs[i]->ptr, recs[i]->size);
 125        if (add_nl) {
 126                i = recs[count - 1]->size;
 127                if (i == 0 || recs[count - 1]->ptr[i - 1] != '\n') {
 128                        if (dest)
 129                                dest[size] = '\n';
 130                        size++;
 131                }
 132        }
 133        return size;
 134}
 135
 136static int xdl_recs_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
 137{
 138        return xdl_recs_copy_0(0, xe, i, count, add_nl, dest);
 139}
 140
 141static int xdl_orig_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
 142{
 143        return xdl_recs_copy_0(1, xe, i, count, add_nl, dest);
 144}
 145
 146/*
 147 * Returns 1 if the i'th line ends in CR/LF (if it is the last line and
 148 * has no eol, the preceding line, if any), 0 if it ends in LF-only, and
 149 * -1 if the line ending cannot be determined.
 150 */
 151static int is_eol_crlf(xdfile_t *file, int i)
 152{
 153        long size;
 154
 155        if (i < file->nrec - 1)
 156                /* All lines before the last *must* end in LF */
 157                return (size = file->recs[i]->size) > 1 &&
 158                        file->recs[i]->ptr[size - 2] == '\r';
 159        if (!file->nrec)
 160                /* Cannot determine eol style from empty file */
 161                return -1;
 162        if ((size = file->recs[i]->size) &&
 163                        file->recs[i]->ptr[size - 1] == '\n')
 164                /* Last line; ends in LF; Is it CR/LF? */
 165                return size > 1 &&
 166                        file->recs[i]->ptr[size - 2] == '\r';
 167        if (!i)
 168                /* The only line has no eol */
 169                return -1;
 170        /* Determine eol from second-to-last line */
 171        return (size = file->recs[i - 1]->size) > 1 &&
 172                file->recs[i - 1]->ptr[size - 2] == '\r';
 173}
 174
 175static int is_cr_needed(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m)
 176{
 177        int needs_cr;
 178
 179        /* Match post-images' preceding, or first, lines' end-of-line style */
 180        needs_cr = is_eol_crlf(&xe1->xdf2, m->i1 ? m->i1 - 1 : 0);
 181        if (needs_cr)
 182                needs_cr = is_eol_crlf(&xe2->xdf2, m->i2 ? m->i2 - 1 : 0);
 183        /* Look at pre-image's first line, unless we already settled on LF */
 184        if (needs_cr)
 185                needs_cr = is_eol_crlf(&xe1->xdf1, 0);
 186        /* If still undecided, use LF-only */
 187        return needs_cr < 0 ? 0 : needs_cr;
 188}
 189
 190static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
 191                              xdfenv_t *xe2, const char *name2,
 192                              const char *name3,
 193                              int size, int i, int style,
 194                              xdmerge_t *m, char *dest, int marker_size)
 195{
 196        int marker1_size = (name1 ? strlen(name1) + 1 : 0);
 197        int marker2_size = (name2 ? strlen(name2) + 1 : 0);
 198        int marker3_size = (name3 ? strlen(name3) + 1 : 0);
 199        int needs_cr = is_cr_needed(xe1, xe2, m);
 200
 201        if (marker_size <= 0)
 202                marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
 203
 204        /* Before conflicting part */
 205        size += xdl_recs_copy(xe1, i, m->i1 - i, 0,
 206                              dest ? dest + size : NULL);
 207
 208        if (!dest) {
 209                size += marker_size + 1 + needs_cr + marker1_size;
 210        } else {
 211                memset(dest + size, '<', marker_size);
 212                size += marker_size;
 213                if (marker1_size) {
 214                        dest[size] = ' ';
 215                        memcpy(dest + size + 1, name1, marker1_size - 1);
 216                        size += marker1_size;
 217                }
 218                if (needs_cr)
 219                        dest[size++] = '\r';
 220                dest[size++] = '\n';
 221        }
 222
 223        /* Postimage from side #1 */
 224        size += xdl_recs_copy(xe1, m->i1, m->chg1, 1,
 225                              dest ? dest + size : NULL);
 226
 227        if (style == XDL_MERGE_DIFF3) {
 228                /* Shared preimage */
 229                if (!dest) {
 230                        size += marker_size + 1 + needs_cr + marker3_size;
 231                } else {
 232                        memset(dest + size, '|', marker_size);
 233                        size += marker_size;
 234                        if (marker3_size) {
 235                                dest[size] = ' ';
 236                                memcpy(dest + size + 1, name3, marker3_size - 1);
 237                                size += marker3_size;
 238                        }
 239                        if (needs_cr)
 240                                dest[size++] = '\r';
 241                        dest[size++] = '\n';
 242                }
 243                size += xdl_orig_copy(xe1, m->i0, m->chg0, 1,
 244                                      dest ? dest + size : NULL);
 245        }
 246
 247        if (!dest) {
 248                size += marker_size + 1 + needs_cr;
 249        } else {
 250                memset(dest + size, '=', marker_size);
 251                size += marker_size;
 252                if (needs_cr)
 253                        dest[size++] = '\r';
 254                dest[size++] = '\n';
 255        }
 256
 257        /* Postimage from side #2 */
 258        size += xdl_recs_copy(xe2, m->i2, m->chg2, 1,
 259                              dest ? dest + size : NULL);
 260        if (!dest) {
 261                size += marker_size + 1 + needs_cr + marker2_size;
 262        } else {
 263                memset(dest + size, '>', marker_size);
 264                size += marker_size;
 265                if (marker2_size) {
 266                        dest[size] = ' ';
 267                        memcpy(dest + size + 1, name2, marker2_size - 1);
 268                        size += marker2_size;
 269                }
 270                if (needs_cr)
 271                        dest[size++] = '\r';
 272                dest[size++] = '\n';
 273        }
 274        return size;
 275}
 276
 277static int xdl_fill_merge_buffer(xdfenv_t *xe1, const char *name1,
 278                                 xdfenv_t *xe2, const char *name2,
 279                                 const char *ancestor_name,
 280                                 int favor,
 281                                 xdmerge_t *m, char *dest, int style,
 282                                 int marker_size)
 283{
 284        int size, i;
 285
 286        for (size = i = 0; m; m = m->next) {
 287                if (favor && !m->mode)
 288                        m->mode = favor;
 289
 290                if (m->mode == 0)
 291                        size = fill_conflict_hunk(xe1, name1, xe2, name2,
 292                                                  ancestor_name,
 293                                                  size, i, style, m, dest,
 294                                                  marker_size);
 295                else if (m->mode & 3) {
 296                        /* Before conflicting part */
 297                        size += xdl_recs_copy(xe1, i, m->i1 - i, 0,
 298                                              dest ? dest + size : NULL);
 299                        /* Postimage from side #1 */
 300                        if (m->mode & 1)
 301                                size += xdl_recs_copy(xe1, m->i1, m->chg1, (m->mode & 2),
 302                                                      dest ? dest + size : NULL);
 303                        /* Postimage from side #2 */
 304                        if (m->mode & 2)
 305                                size += xdl_recs_copy(xe2, m->i2, m->chg2, 0,
 306                                                      dest ? dest + size : NULL);
 307                } else
 308                        continue;
 309                i = m->i1 + m->chg1;
 310        }
 311        size += xdl_recs_copy(xe1, i, xe1->xdf2.nrec - i, 0,
 312                              dest ? dest + size : NULL);
 313        return size;
 314}
 315
 316/*
 317 * Sometimes, changes are not quite identical, but differ in only a few
 318 * lines. Try hard to show only these few lines as conflicting.
 319 */
 320static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
 321                xpparam_t const *xpp)
 322{
 323        for (; m; m = m->next) {
 324                mmfile_t t1, t2;
 325                xdfenv_t xe;
 326                xdchange_t *xscr, *x;
 327                int i1 = m->i1, i2 = m->i2;
 328
 329                /* let's handle just the conflicts */
 330                if (m->mode)
 331                        continue;
 332
 333                /* no sense refining a conflict when one side is empty */
 334                if (m->chg1 == 0 || m->chg2 == 0)
 335                        continue;
 336
 337                /*
 338                 * This probably does not work outside git, since
 339                 * we have a very simple mmfile structure.
 340                 */
 341                t1.ptr = (char *)xe1->xdf2.recs[m->i1]->ptr;
 342                t1.size = xe1->xdf2.recs[m->i1 + m->chg1 - 1]->ptr
 343                        + xe1->xdf2.recs[m->i1 + m->chg1 - 1]->size - t1.ptr;
 344                t2.ptr = (char *)xe2->xdf2.recs[m->i2]->ptr;
 345                t2.size = xe2->xdf2.recs[m->i2 + m->chg2 - 1]->ptr
 346                        + xe2->xdf2.recs[m->i2 + m->chg2 - 1]->size - t2.ptr;
 347                if (xdl_do_diff(&t1, &t2, xpp, &xe) < 0)
 348                        return -1;
 349                if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
 350                    xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
 351                    xdl_build_script(&xe, &xscr) < 0) {
 352                        xdl_free_env(&xe);
 353                        return -1;
 354                }
 355                if (!xscr) {
 356                        /* If this happens, the changes are identical. */
 357                        xdl_free_env(&xe);
 358                        m->mode = 4;
 359                        continue;
 360                }
 361                x = xscr;
 362                m->i1 = xscr->i1 + i1;
 363                m->chg1 = xscr->chg1;
 364                m->i2 = xscr->i2 + i2;
 365                m->chg2 = xscr->chg2;
 366                while (xscr->next) {
 367                        xdmerge_t *m2 = xdl_malloc(sizeof(xdmerge_t));
 368                        if (!m2) {
 369                                xdl_free_env(&xe);
 370                                xdl_free_script(x);
 371                                return -1;
 372                        }
 373                        xscr = xscr->next;
 374                        m2->next = m->next;
 375                        m->next = m2;
 376                        m = m2;
 377                        m->mode = 0;
 378                        m->i1 = xscr->i1 + i1;
 379                        m->chg1 = xscr->chg1;
 380                        m->i2 = xscr->i2 + i2;
 381                        m->chg2 = xscr->chg2;
 382                }
 383                xdl_free_env(&xe);
 384                xdl_free_script(x);
 385        }
 386        return 0;
 387}
 388
 389static int line_contains_alnum(const char *ptr, long size)
 390{
 391        while (size--)
 392                if (isalnum((unsigned char)*(ptr++)))
 393                        return 1;
 394        return 0;
 395}
 396
 397static int lines_contain_alnum(xdfenv_t *xe, int i, int chg)
 398{
 399        for (; chg; chg--, i++)
 400                if (line_contains_alnum(xe->xdf2.recs[i]->ptr,
 401                                xe->xdf2.recs[i]->size))
 402                        return 1;
 403        return 0;
 404}
 405
 406/*
 407 * This function merges m and m->next, marking everything between those hunks
 408 * as conflicting, too.
 409 */
 410static void xdl_merge_two_conflicts(xdmerge_t *m)
 411{
 412        xdmerge_t *next_m = m->next;
 413        m->chg1 = next_m->i1 + next_m->chg1 - m->i1;
 414        m->chg2 = next_m->i2 + next_m->chg2 - m->i2;
 415        m->next = next_m->next;
 416        free(next_m);
 417}
 418
 419/*
 420 * If there are less than 3 non-conflicting lines between conflicts,
 421 * it appears simpler -- because it takes up less (or as many) lines --
 422 * if the lines are moved into the conflicts.
 423 */
 424static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m,
 425                                      int simplify_if_no_alnum)
 426{
 427        int result = 0;
 428
 429        if (!m)
 430                return result;
 431        for (;;) {
 432                xdmerge_t *next_m = m->next;
 433                int begin, end;
 434
 435                if (!next_m)
 436                        return result;
 437
 438                begin = m->i1 + m->chg1;
 439                end = next_m->i1;
 440
 441                if (m->mode != 0 || next_m->mode != 0 ||
 442                    (end - begin > 3 &&
 443                     (!simplify_if_no_alnum ||
 444                      lines_contain_alnum(xe1, begin, end - begin)))) {
 445                        m = next_m;
 446                } else {
 447                        result++;
 448                        xdl_merge_two_conflicts(m);
 449                }
 450        }
 451}
 452
 453/*
 454 * level == 0: mark all overlapping changes as conflict
 455 * level == 1: mark overlapping changes as conflict only if not identical
 456 * level == 2: analyze non-identical changes for minimal conflict set
 457 * level == 3: analyze non-identical changes for minimal conflict set, but
 458 *             treat hunks not containing any letter or number as conflicting
 459 *
 460 * returns < 0 on error, == 0 for no conflicts, else number of conflicts
 461 */
 462static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1,
 463                xdfenv_t *xe2, xdchange_t *xscr2,
 464                xmparam_t const *xmp, mmbuffer_t *result)
 465{
 466        xdmerge_t *changes, *c;
 467        xpparam_t const *xpp = &xmp->xpp;
 468        const char *const ancestor_name = xmp->ancestor;
 469        const char *const name1 = xmp->file1;
 470        const char *const name2 = xmp->file2;
 471        int i0, i1, i2, chg0, chg1, chg2;
 472        int level = xmp->level;
 473        int style = xmp->style;
 474        int favor = xmp->favor;
 475
 476        if (style == XDL_MERGE_DIFF3) {
 477                /*
 478                 * "diff3 -m" output does not make sense for anything
 479                 * more aggressive than XDL_MERGE_EAGER.
 480                 */
 481                if (XDL_MERGE_EAGER < level)
 482                        level = XDL_MERGE_EAGER;
 483        }
 484
 485        c = changes = NULL;
 486
 487        while (xscr1 && xscr2) {
 488                if (!changes)
 489                        changes = c;
 490                if (xscr1->i1 + xscr1->chg1 < xscr2->i1) {
 491                        i0 = xscr1->i1;
 492                        i1 = xscr1->i2;
 493                        i2 = xscr2->i2 - xscr2->i1 + xscr1->i1;
 494                        chg0 = xscr1->chg1;
 495                        chg1 = xscr1->chg2;
 496                        chg2 = xscr1->chg1;
 497                        if (xdl_append_merge(&c, 1,
 498                                             i0, chg0, i1, chg1, i2, chg2)) {
 499                                xdl_cleanup_merge(changes);
 500                                return -1;
 501                        }
 502                        xscr1 = xscr1->next;
 503                        continue;
 504                }
 505                if (xscr2->i1 + xscr2->chg1 < xscr1->i1) {
 506                        i0 = xscr2->i1;
 507                        i1 = xscr1->i2 - xscr1->i1 + xscr2->i1;
 508                        i2 = xscr2->i2;
 509                        chg0 = xscr2->chg1;
 510                        chg1 = xscr2->chg1;
 511                        chg2 = xscr2->chg2;
 512                        if (xdl_append_merge(&c, 2,
 513                                             i0, chg0, i1, chg1, i2, chg2)) {
 514                                xdl_cleanup_merge(changes);
 515                                return -1;
 516                        }
 517                        xscr2 = xscr2->next;
 518                        continue;
 519                }
 520                if (level == XDL_MERGE_MINIMAL || xscr1->i1 != xscr2->i1 ||
 521                                xscr1->chg1 != xscr2->chg1 ||
 522                                xscr1->chg2 != xscr2->chg2 ||
 523                                xdl_merge_cmp_lines(xe1, xscr1->i2,
 524                                        xe2, xscr2->i2,
 525                                        xscr1->chg2, xpp->flags)) {
 526                        /* conflict */
 527                        int off = xscr1->i1 - xscr2->i1;
 528                        int ffo = off + xscr1->chg1 - xscr2->chg1;
 529
 530                        i0 = xscr1->i1;
 531                        i1 = xscr1->i2;
 532                        i2 = xscr2->i2;
 533                        if (off > 0) {
 534                                i0 -= off;
 535                                i1 -= off;
 536                        }
 537                        else
 538                                i2 += off;
 539                        chg0 = xscr1->i1 + xscr1->chg1 - i0;
 540                        chg1 = xscr1->i2 + xscr1->chg2 - i1;
 541                        chg2 = xscr2->i2 + xscr2->chg2 - i2;
 542                        if (ffo < 0) {
 543                                chg0 -= ffo;
 544                                chg1 -= ffo;
 545                        } else
 546                                chg2 += ffo;
 547                        if (xdl_append_merge(&c, 0,
 548                                             i0, chg0, i1, chg1, i2, chg2)) {
 549                                xdl_cleanup_merge(changes);
 550                                return -1;
 551                        }
 552                }
 553
 554                i1 = xscr1->i1 + xscr1->chg1;
 555                i2 = xscr2->i1 + xscr2->chg1;
 556
 557                if (i1 >= i2)
 558                        xscr2 = xscr2->next;
 559                if (i2 >= i1)
 560                        xscr1 = xscr1->next;
 561        }
 562        while (xscr1) {
 563                if (!changes)
 564                        changes = c;
 565                i0 = xscr1->i1;
 566                i1 = xscr1->i2;
 567                i2 = xscr1->i1 + xe2->xdf2.nrec - xe2->xdf1.nrec;
 568                chg0 = xscr1->chg1;
 569                chg1 = xscr1->chg2;
 570                chg2 = xscr1->chg1;
 571                if (xdl_append_merge(&c, 1,
 572                                     i0, chg0, i1, chg1, i2, chg2)) {
 573                        xdl_cleanup_merge(changes);
 574                        return -1;
 575                }
 576                xscr1 = xscr1->next;
 577        }
 578        while (xscr2) {
 579                if (!changes)
 580                        changes = c;
 581                i0 = xscr2->i1;
 582                i1 = xscr2->i1 + xe1->xdf2.nrec - xe1->xdf1.nrec;
 583                i2 = xscr2->i2;
 584                chg0 = xscr2->chg1;
 585                chg1 = xscr2->chg1;
 586                chg2 = xscr2->chg2;
 587                if (xdl_append_merge(&c, 2,
 588                                     i0, chg0, i1, chg1, i2, chg2)) {
 589                        xdl_cleanup_merge(changes);
 590                        return -1;
 591                }
 592                xscr2 = xscr2->next;
 593        }
 594        if (!changes)
 595                changes = c;
 596        /* refine conflicts */
 597        if (XDL_MERGE_ZEALOUS <= level &&
 598            (xdl_refine_conflicts(xe1, xe2, changes, xpp) < 0 ||
 599             xdl_simplify_non_conflicts(xe1, changes,
 600                                        XDL_MERGE_ZEALOUS < level) < 0)) {
 601                xdl_cleanup_merge(changes);
 602                return -1;
 603        }
 604        /* output */
 605        if (result) {
 606                int marker_size = xmp->marker_size;
 607                int size = xdl_fill_merge_buffer(xe1, name1, xe2, name2,
 608                                                 ancestor_name,
 609                                                 favor, changes, NULL, style,
 610                                                 marker_size);
 611                result->ptr = xdl_malloc(size);
 612                if (!result->ptr) {
 613                        xdl_cleanup_merge(changes);
 614                        return -1;
 615                }
 616                result->size = size;
 617                xdl_fill_merge_buffer(xe1, name1, xe2, name2,
 618                                      ancestor_name, favor, changes,
 619                                      result->ptr, style, marker_size);
 620        }
 621        return xdl_cleanup_merge(changes);
 622}
 623
 624int xdl_merge(mmfile_t *orig, mmfile_t *mf1, mmfile_t *mf2,
 625                xmparam_t const *xmp, mmbuffer_t *result)
 626{
 627        xdchange_t *xscr1, *xscr2;
 628        xdfenv_t xe1, xe2;
 629        int status;
 630        xpparam_t const *xpp = &xmp->xpp;
 631
 632        result->ptr = NULL;
 633        result->size = 0;
 634
 635        if (xdl_do_diff(orig, mf1, xpp, &xe1) < 0 ||
 636                        xdl_do_diff(orig, mf2, xpp, &xe2) < 0) {
 637                return -1;
 638        }
 639        if (xdl_change_compact(&xe1.xdf1, &xe1.xdf2, xpp->flags) < 0 ||
 640            xdl_change_compact(&xe1.xdf2, &xe1.xdf1, xpp->flags) < 0 ||
 641            xdl_build_script(&xe1, &xscr1) < 0) {
 642                xdl_free_env(&xe1);
 643                return -1;
 644        }
 645        if (xdl_change_compact(&xe2.xdf1, &xe2.xdf2, xpp->flags) < 0 ||
 646            xdl_change_compact(&xe2.xdf2, &xe2.xdf1, xpp->flags) < 0 ||
 647            xdl_build_script(&xe2, &xscr2) < 0) {
 648                xdl_free_env(&xe2);
 649                return -1;
 650        }
 651        status = 0;
 652        if (!xscr1) {
 653                result->ptr = xdl_malloc(mf2->size);
 654                memcpy(result->ptr, mf2->ptr, mf2->size);
 655                result->size = mf2->size;
 656        } else if (!xscr2) {
 657                result->ptr = xdl_malloc(mf1->size);
 658                memcpy(result->ptr, mf1->ptr, mf1->size);
 659                result->size = mf1->size;
 660        } else {
 661                status = xdl_do_merge(&xe1, xscr1,
 662                                      &xe2, xscr2,
 663                                      xmp, result);
 664        }
 665        xdl_free_script(xscr1);
 666        xdl_free_script(xscr2);
 667
 668        xdl_free_env(&xe1);
 669        xdl_free_env(&xe2);
 670
 671        return status;
 672}