comparison mercurial/thirdparty/xdiff/xmerge.c @ 36671:34e2ff1f9cd8

xdiff: vendor xdiff library from git

Vendor git's xdiff library from git commit
d7c6c2369d7c6c2369ac21141b7c6cceaebc6414ec3da14ad using GPL2+ license.

There is another recent user report that hg diff generates suboptimal
result. It seems the fix to issue4074 isn't good enough. I crafted some
other interesting cases, and hg diff barely has any advantage compared with
gnu diffutils or git diff.

| testcase | gnu diffutils |      hg diff |   git diff |
|          |    lines time |   lines time | lines time |
| patience |        6 0.00 |     602 0.08 |     6 0.00 |
|   random |    91772 0.90 |  109462 0.70 | 91772 0.24 |
|     json |        2 0.03 | 1264814 1.81 |     2 0.29 |

"lines" means the size of the output, i.e. the count of "+/-" lines. "time"
means seconds needed to do the calculation. Both are the smaller the better.
"hg diff" counts Python startup overhead.

Git and GNU diffutils generate optimal results. For the "json" case, git can
have an optimization that does a scan for common prefix and suffix first,
and match them if the length is greater than half of the text. See
https://neil.fraser.name/news/2006/03/12/. That would make git the fastest
for all above cases.

About testcases:

patience:
Aiming for the weakness of the greedy "patience diff" algorithm.  Using
git's patience diff option would also get suboptimal result. Generated using
the Python script:

```
open('a', 'w').write('\n'.join(list('a' + 'x' * 300 + 'u' + 'x' * 700 + 'a\n')))
open('b', 'w').write('\n'.join(list('b' + 'x' * 700 + 'u' + 'x' * 300 + 'b\n')))
```

random:
Generated using the script in `test-issue4074.t`. It practically makes the
algorithm suffer. Impressively, git wins in both performance and diff
quality.

json:
The recent user reported case. It's a single line movement near the end of a
very large (800K lines) JSON file.

Test Plan:
Code taken as-is.

Differential Revision: https://phab.mercurial-scm.org/D2572

# no-check-commit for vendored code

36671:34e2ff1f9cd8

/*
 *  LibXDiff by Davide Libenzi ( File Differential Library )
 *  Copyright (C) 2003-2006 Davide Libenzi, Johannes E. Schindelin
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, see
 *  <http://www.gnu.org/licenses/>.
 *
 *  Davide Libenzi <[e-mail]>
 *
 */

#include "xinclude.h"

typedef struct s_xdmerge {
	struct s_xdmerge *next;
	/*
	 * 0 = conflict,
	 * 1 = no conflict, take first,
	 * 2 = no conflict, take second.
	 * 3 = no conflict, take both.
	 */
	int mode;
	/*
	 * These point at the respective postimages.  E.g. <i1,chg1> is
	 * how side #1 wants to change the common ancestor; if there is no
	 * overlap, lines before i1 in the postimage of side #1 appear
	 * in the merge result as a region touched by neither side.
	 */
	long i1, i2;
	long chg1, chg2;
	/*
	 * These point at the preimage; of course there is just one
	 * preimage, that is from the shared common ancestor.
	 */
	long i0;
	long chg0;
} xdmerge_t;

static int xdl_append_merge(xdmerge_t **merge, int mode,
			    long i0, long chg0,
			    long i1, long chg1,
			    long i2, long chg2)
{
	xdmerge_t *m = *merge;
	if (m && (i1 <= m->i1 + m->chg1 || i2 <= m->i2 + m->chg2)) {
		if (mode != m->mode)
			m->mode = 0;
		m->chg0 = i0 + chg0 - m->i0;
		m->chg1 = i1 + chg1 - m->i1;
		m->chg2 = i2 + chg2 - m->i2;
	} else {
		m = xdl_malloc(sizeof(xdmerge_t));
		if (!m)
			return -1;
		m->next = NULL;
		m->mode = mode;
		m->i0 = i0;
		m->chg0 = chg0;
		m->i1 = i1;
		m->chg1 = chg1;
		m->i2 = i2;
		m->chg2 = chg2;
		if (*merge)
			(*merge)->next = m;
		*merge = m;
	}
	return 0;
}

static int xdl_cleanup_merge(xdmerge_t *c)
{
	int count = 0;
	xdmerge_t *next_c;

	/* were there conflicts? */
	for (; c; c = next_c) {
		if (c->mode == 0)
			count++;
		next_c = c->next;
		free(c);
	}
	return count;
}

static int xdl_merge_cmp_lines(xdfenv_t *xe1, int i1, xdfenv_t *xe2, int i2,
		int line_count, long flags)
{
	int i;
	xrecord_t **rec1 = xe1->xdf2.recs + i1;
	xrecord_t **rec2 = xe2->xdf2.recs + i2;

	for (i = 0; i < line_count; i++) {
		int result = xdl_recmatch(rec1[i]->ptr, rec1[i]->size,
			rec2[i]->ptr, rec2[i]->size, flags);
		if (!result)
			return -1;
	}
	return 0;
}

static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
{
	xrecord_t **recs;
	int size = 0;

	recs = (use_orig ? xe->xdf1.recs : xe->xdf2.recs) + i;

	if (count < 1)
		return 0;

	for (i = 0; i < count; size += recs[i++]->size)
		if (dest)
			memcpy(dest + size, recs[i]->ptr, recs[i]->size);
	if (add_nl) {
		i = recs[count - 1]->size;
		if (i == 0 || recs[count - 1]->ptr[i - 1] != '\n') {
			if (needs_cr) {
				if (dest)
					dest[size] = '\r';
				size++;
			}

			if (dest)
				dest[size] = '\n';
			size++;
		}
	}
	return size;
}

static int xdl_recs_copy(xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
{
	return xdl_recs_copy_0(0, xe, i, count, needs_cr, add_nl, dest);
}

static int xdl_orig_copy(xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
{
	return xdl_recs_copy_0(1, xe, i, count, needs_cr, add_nl, dest);
}

/*
 * Returns 1 if the i'th line ends in CR/LF (if it is the last line and
 * has no eol, the preceding line, if any), 0 if it ends in LF-only, and
 * -1 if the line ending cannot be determined.
 */
static int is_eol_crlf(xdfile_t *file, int i)
{
	long size;

	if (i < file->nrec - 1)
		/* All lines before the last *must* end in LF */
		return (size = file->recs[i]->size) > 1 &&
			file->recs[i]->ptr[size - 2] == '\r';
	if (!file->nrec)
		/* Cannot determine eol style from empty file */
		return -1;
	if ((size = file->recs[i]->size) &&
			file->recs[i]->ptr[size - 1] == '\n')
		/* Last line; ends in LF; Is it CR/LF? */
		return size > 1 &&
			file->recs[i]->ptr[size - 2] == '\r';
	if (!i)
		/* The only line has no eol */
		return -1;
	/* Determine eol from second-to-last line */
	return (size = file->recs[i - 1]->size) > 1 &&
		file->recs[i - 1]->ptr[size - 2] == '\r';
}

static int is_cr_needed(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m)
{
	int needs_cr;

	/* Match post-images' preceding, or first, lines' end-of-line style */
	needs_cr = is_eol_crlf(&xe1->xdf2, m->i1 ? m->i1 - 1 : 0);
	if (needs_cr)
		needs_cr = is_eol_crlf(&xe2->xdf2, m->i2 ? m->i2 - 1 : 0);
	/* Look at pre-image's first line, unless we already settled on LF */
	if (needs_cr)
		needs_cr = is_eol_crlf(&xe1->xdf1, 0);
	/* If still undecided, use LF-only */
	return needs_cr < 0 ? 0 : needs_cr;
}

static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
			      xdfenv_t *xe2, const char *name2,
			      const char *name3,
			      int size, int i, int style,
			      xdmerge_t *m, char *dest, int marker_size)
{
	int marker1_size = (name1 ? strlen(name1) + 1 : 0);
	int marker2_size = (name2 ? strlen(name2) + 1 : 0);
	int marker3_size = (name3 ? strlen(name3) + 1 : 0);
	int needs_cr = is_cr_needed(xe1, xe2, m);

	if (marker_size <= 0)
		marker_size = DEFAULT_CONFLICT_MARKER_SIZE;

	/* Before conflicting part */
	size += xdl_recs_copy(xe1, i, m->i1 - i, 0, 0,
			      dest ? dest + size : NULL);

	if (!dest) {
		size += marker_size + 1 + needs_cr + marker1_size;
	} else {
		memset(dest + size, '<', marker_size);
		size += marker_size;
		if (marker1_size) {
			dest[size] = ' ';
			memcpy(dest + size + 1, name1, marker1_size - 1);
			size += marker1_size;
		}
		if (needs_cr)
			dest[size++] = '\r';
		dest[size++] = '\n';
	}

	/* Postimage from side #1 */
	size += xdl_recs_copy(xe1, m->i1, m->chg1, needs_cr, 1,
			      dest ? dest + size : NULL);

	if (style == XDL_MERGE_DIFF3) {
		/* Shared preimage */
		if (!dest) {
			size += marker_size + 1 + needs_cr + marker3_size;
		} else {
			memset(dest + size, '|', marker_size);
			size += marker_size;
			if (marker3_size) {
				dest[size] = ' ';
				memcpy(dest + size + 1, name3, marker3_size - 1);
				size += marker3_size;
			}
			if (needs_cr)
				dest[size++] = '\r';
			dest[size++] = '\n';
		}
		size += xdl_orig_copy(xe1, m->i0, m->chg0, needs_cr, 1,
				      dest ? dest + size : NULL);
	}

	if (!dest) {
		size += marker_size + 1 + needs_cr;
	} else {
		memset(dest + size, '=', marker_size);
		size += marker_size;
		if (needs_cr)
			dest[size++] = '\r';
		dest[size++] = '\n';
	}

	/* Postimage from side #2 */
	size += xdl_recs_copy(xe2, m->i2, m->chg2, needs_cr, 1,
			      dest ? dest + size : NULL);
	if (!dest) {
		size += marker_size + 1 + needs_cr + marker2_size;
	} else {
		memset(dest + size, '>', marker_size);
		size += marker_size;
		if (marker2_size) {
			dest[size] = ' ';
			memcpy(dest + size + 1, name2, marker2_size - 1);
			size += marker2_size;
		}
		if (needs_cr)
			dest[size++] = '\r';
		dest[size++] = '\n';
	}
	return size;
}

static int xdl_fill_merge_buffer(xdfenv_t *xe1, const char *name1,
				 xdfenv_t *xe2, const char *name2,
				 const char *ancestor_name,
				 int favor,
				 xdmerge_t *m, char *dest, int style,
				 int marker_size)
{
	int size, i;

	for (size = i = 0; m; m = m->next) {
		if (favor && !m->mode)
			m->mode = favor;

		if (m->mode == 0)
			size = fill_conflict_hunk(xe1, name1, xe2, name2,
						  ancestor_name,
						  size, i, style, m, dest,
						  marker_size);
		else if (m->mode & 3) {
			/* Before conflicting part */
			size += xdl_recs_copy(xe1, i, m->i1 - i, 0, 0,
					      dest ? dest + size : NULL);
			/* Postimage from side #1 */
			if (m->mode & 1) {
				int needs_cr = is_cr_needed(xe1, xe2, m);

				size += xdl_recs_copy(xe1, m->i1, m->chg1, needs_cr, (m->mode & 2),
						      dest ? dest + size : NULL);
			}
			/* Postimage from side #2 */
			if (m->mode & 2)
				size += xdl_recs_copy(xe2, m->i2, m->chg2, 0, 0,
						      dest ? dest + size : NULL);
		} else
			continue;
		i = m->i1 + m->chg1;
	}
	size += xdl_recs_copy(xe1, i, xe1->xdf2.nrec - i, 0, 0,
			      dest ? dest + size : NULL);
	return size;
}

/*
 * Sometimes, changes are not quite identical, but differ in only a few
 * lines. Try hard to show only these few lines as conflicting.
 */
static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
		xpparam_t const *xpp)
{
	for (; m; m = m->next) {
		mmfile_t t1, t2;
		xdfenv_t xe;
		xdchange_t *xscr, *x;
		int i1 = m->i1, i2 = m->i2;

		/* let's handle just the conflicts */
		if (m->mode)
			continue;

		/* no sense refining a conflict when one side is empty */
		if (m->chg1 == 0 || m->chg2 == 0)
			continue;

		/*
		 * This probably does not work outside git, since
		 * we have a very simple mmfile structure.
		 */
		t1.ptr = (char *)xe1->xdf2.recs[m->i1]->ptr;
		t1.size = xe1->xdf2.recs[m->i1 + m->chg1 - 1]->ptr
			+ xe1->xdf2.recs[m->i1 + m->chg1 - 1]->size - t1.ptr;
		t2.ptr = (char *)xe2->xdf2.recs[m->i2]->ptr;
		t2.size = xe2->xdf2.recs[m->i2 + m->chg2 - 1]->ptr
			+ xe2->xdf2.recs[m->i2 + m->chg2 - 1]->size - t2.ptr;
		if (xdl_do_diff(&t1, &t2, xpp, &xe) < 0)
			return -1;
		if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
		    xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
		    xdl_build_script(&xe, &xscr) < 0) {
			xdl_free_env(&xe);
			return -1;
		}
		if (!xscr) {
			/* If this happens, the changes are identical. */
			xdl_free_env(&xe);
			m->mode = 4;
			continue;
		}
		x = xscr;
		m->i1 = xscr->i1 + i1;
		m->chg1 = xscr->chg1;
		m->i2 = xscr->i2 + i2;
		m->chg2 = xscr->chg2;
		while (xscr->next) {
			xdmerge_t *m2 = xdl_malloc(sizeof(xdmerge_t));
			if (!m2) {
				xdl_free_env(&xe);
				xdl_free_script(x);
				return -1;
			}
			xscr = xscr->next;
			m2->next = m->next;
			m->next = m2;
			m = m2;
			m->mode = 0;
			m->i1 = xscr->i1 + i1;
			m->chg1 = xscr->chg1;
			m->i2 = xscr->i2 + i2;
			m->chg2 = xscr->chg2;
		}
		xdl_free_env(&xe);
		xdl_free_script(x);
	}
	return 0;
}

static int line_contains_alnum(const char *ptr, long size)
{
	while (size--)
		if (isalnum((unsigned char)*(ptr++)))
			return 1;
	return 0;
}

static int lines_contain_alnum(xdfenv_t *xe, int i, int chg)
{
	for (; chg; chg--, i++)
		if (line_contains_alnum(xe->xdf2.recs[i]->ptr,
				xe->xdf2.recs[i]->size))
			return 1;
	return 0;
}

/*
 * This function merges m and m->next, marking everything between those hunks
 * as conflicting, too.
 */
static void xdl_merge_two_conflicts(xdmerge_t *m)
{
	xdmerge_t *next_m = m->next;
	m->chg1 = next_m->i1 + next_m->chg1 - m->i1;
	m->chg2 = next_m->i2 + next_m->chg2 - m->i2;
	m->next = next_m->next;
	free(next_m);
}

/*
 * If there are less than 3 non-conflicting lines between conflicts,
 * it appears simpler -- because it takes up less (or as many) lines --
 * if the lines are moved into the conflicts.
 */
static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m,
				      int simplify_if_no_alnum)
{
	int result = 0;

	if (!m)
		return result;
	for (;;) {
		xdmerge_t *next_m = m->next;
		int begin, end;

		if (!next_m)
			return result;

		begin = m->i1 + m->chg1;
		end = next_m->i1;

		if (m->mode != 0 || next_m->mode != 0 ||
		    (end - begin > 3 &&
		     (!simplify_if_no_alnum ||
		      lines_contain_alnum(xe1, begin, end - begin)))) {
			m = next_m;
		} else {
			result++;
			xdl_merge_two_conflicts(m);
		}
	}
}

/*
 * level == 0: mark all overlapping changes as conflict
 * level == 1: mark overlapping changes as conflict only if not identical
 * level == 2: analyze non-identical changes for minimal conflict set
 * level == 3: analyze non-identical changes for minimal conflict set, but
 *             treat hunks not containing any letter or number as conflicting
 *
 * returns < 0 on error, == 0 for no conflicts, else number of conflicts
 */
static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1,
		xdfenv_t *xe2, xdchange_t *xscr2,
		xmparam_t const *xmp, mmbuffer_t *result)
{
	xdmerge_t *changes, *c;
	xpparam_t const *xpp = &xmp->xpp;
	const char *const ancestor_name = xmp->ancestor;
	const char *const name1 = xmp->file1;
	const char *const name2 = xmp->file2;
	int i0, i1, i2, chg0, chg1, chg2;
	int level = xmp->level;
	int style = xmp->style;
	int favor = xmp->favor;

	if (style == XDL_MERGE_DIFF3) {
		/*
		 * "diff3 -m" output does not make sense for anything
		 * more aggressive than XDL_MERGE_EAGER.
		 */
		if (XDL_MERGE_EAGER < level)
			level = XDL_MERGE_EAGER;
	}

	c = changes = NULL;

	while (xscr1 && xscr2) {
		if (!changes)
			changes = c;
		if (xscr1->i1 + xscr1->chg1 < xscr2->i1) {
			i0 = xscr1->i1;
			i1 = xscr1->i2;
			i2 = xscr2->i2 - xscr2->i1 + xscr1->i1;
			chg0 = xscr1->chg1;
			chg1 = xscr1->chg2;
			chg2 = xscr1->chg1;
			if (xdl_append_merge(&c, 1,
					     i0, chg0, i1, chg1, i2, chg2)) {
				xdl_cleanup_merge(changes);
				return -1;
			}
			xscr1 = xscr1->next;
			continue;
		}
		if (xscr2->i1 + xscr2->chg1 < xscr1->i1) {
			i0 = xscr2->i1;
			i1 = xscr1->i2 - xscr1->i1 + xscr2->i1;
			i2 = xscr2->i2;
			chg0 = xscr2->chg1;
			chg1 = xscr2->chg1;
			chg2 = xscr2->chg2;
			if (xdl_append_merge(&c, 2,
					     i0, chg0, i1, chg1, i2, chg2)) {
				xdl_cleanup_merge(changes);
				return -1;
			}
			xscr2 = xscr2->next;
			continue;
		}
		if (level == XDL_MERGE_MINIMAL || xscr1->i1 != xscr2->i1 ||
				xscr1->chg1 != xscr2->chg1 ||
				xscr1->chg2 != xscr2->chg2 ||
				xdl_merge_cmp_lines(xe1, xscr1->i2,
					xe2, xscr2->i2,
					xscr1->chg2, xpp->flags)) {
			/* conflict */
			int off = xscr1->i1 - xscr2->i1;
			int ffo = off + xscr1->chg1 - xscr2->chg1;

			i0 = xscr1->i1;
			i1 = xscr1->i2;
			i2 = xscr2->i2;
			if (off > 0) {
				i0 -= off;
				i1 -= off;
			}
			else
				i2 += off;
			chg0 = xscr1->i1 + xscr1->chg1 - i0;
			chg1 = xscr1->i2 + xscr1->chg2 - i1;
			chg2 = xscr2->i2 + xscr2->chg2 - i2;
			if (ffo < 0) {
				chg0 -= ffo;
				chg1 -= ffo;
			} else
				chg2 += ffo;
			if (xdl_append_merge(&c, 0,
					     i0, chg0, i1, chg1, i2, chg2)) {
				xdl_cleanup_merge(changes);
				return -1;
			}
		}

		i1 = xscr1->i1 + xscr1->chg1;
		i2 = xscr2->i1 + xscr2->chg1;

		if (i1 >= i2)
			xscr2 = xscr2->next;
		if (i2 >= i1)
			xscr1 = xscr1->next;
	}
	while (xscr1) {
		if (!changes)
			changes = c;
		i0 = xscr1->i1;
		i1 = xscr1->i2;
		i2 = xscr1->i1 + xe2->xdf2.nrec - xe2->xdf1.nrec;
		chg0 = xscr1->chg1;
		chg1 = xscr1->chg2;
		chg2 = xscr1->chg1;
		if (xdl_append_merge(&c, 1,
				     i0, chg0, i1, chg1, i2, chg2)) {
			xdl_cleanup_merge(changes);
			return -1;
		}
		xscr1 = xscr1->next;
	}
	while (xscr2) {
		if (!changes)
			changes = c;
		i0 = xscr2->i1;
		i1 = xscr2->i1 + xe1->xdf2.nrec - xe1->xdf1.nrec;
		i2 = xscr2->i2;
		chg0 = xscr2->chg1;
		chg1 = xscr2->chg1;
		chg2 = xscr2->chg2;
		if (xdl_append_merge(&c, 2,
				     i0, chg0, i1, chg1, i2, chg2)) {
			xdl_cleanup_merge(changes);
			return -1;
		}
		xscr2 = xscr2->next;
	}
	if (!changes)
		changes = c;
	/* refine conflicts */
	if (XDL_MERGE_ZEALOUS <= level &&
	    (xdl_refine_conflicts(xe1, xe2, changes, xpp) < 0 ||
	     xdl_simplify_non_conflicts(xe1, changes,
					XDL_MERGE_ZEALOUS < level) < 0)) {
		xdl_cleanup_merge(changes);
		return -1;
	}
	/* output */
	if (result) {
		int marker_size = xmp->marker_size;
		int size = xdl_fill_merge_buffer(xe1, name1, xe2, name2,
						 ancestor_name,
						 favor, changes, NULL, style,
						 marker_size);
		result->ptr = xdl_malloc(size);
		if (!result->ptr) {
			xdl_cleanup_merge(changes);
			return -1;
		}
		result->size = size;
		xdl_fill_merge_buffer(xe1, name1, xe2, name2,
				      ancestor_name, favor, changes,
				      result->ptr, style, marker_size);
	}
	return xdl_cleanup_merge(changes);
}

int xdl_merge(mmfile_t *orig, mmfile_t *mf1, mmfile_t *mf2,
		xmparam_t const *xmp, mmbuffer_t *result)
{
	xdchange_t *xscr1, *xscr2;
	xdfenv_t xe1, xe2;
	int status;
	xpparam_t const *xpp = &xmp->xpp;

	result->ptr = NULL;
	result->size = 0;

	if (xdl_do_diff(orig, mf1, xpp, &xe1) < 0) {
		return -1;
	}
	if (xdl_do_diff(orig, mf2, xpp, &xe2) < 0) {
		xdl_free_env(&xe1);
		return -1;
	}
	if (xdl_change_compact(&xe1.xdf1, &xe1.xdf2, xpp->flags) < 0 ||
	    xdl_change_compact(&xe1.xdf2, &xe1.xdf1, xpp->flags) < 0 ||
	    xdl_build_script(&xe1, &xscr1) < 0) {
		xdl_free_env(&xe1);
		return -1;
	}
	if (xdl_change_compact(&xe2.xdf1, &xe2.xdf2, xpp->flags) < 0 ||
	    xdl_change_compact(&xe2.xdf2, &xe2.xdf1, xpp->flags) < 0 ||
	    xdl_build_script(&xe2, &xscr2) < 0) {
		xdl_free_script(xscr1);
		xdl_free_env(&xe1);
		xdl_free_env(&xe2);
		return -1;
	}
	status = 0;
	if (!xscr1) {
		result->ptr = xdl_malloc(mf2->size);
		memcpy(result->ptr, mf2->ptr, mf2->size);
		result->size = mf2->size;
	} else if (!xscr2) {
		result->ptr = xdl_malloc(mf1->size);
		memcpy(result->ptr, mf1->ptr, mf1->size);
		result->size = mf1->size;
	} else {
		status = xdl_do_merge(&xe1, xscr1,
				      &xe2, xscr2,
				      xmp, result);
	}
	xdl_free_script(xscr1);
	xdl_free_script(xscr2);

	xdl_free_env(&xe1);
	xdl_free_env(&xe2);

	return status;
}