view mercurial/thirdparty/xdiff/xdiff.h @ 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

/*
 *  LibXDiff by Davide Libenzi ( File Differential Library )
 *  Copyright (C) 2003  Davide Libenzi
 *
 *  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]>
 *
 */

#if !defined(XDIFF_H)
#define XDIFF_H

#ifdef __cplusplus
extern "C" {
#endif /* #ifdef __cplusplus */

/* xpparm_t.flags */
#define XDF_NEED_MINIMAL (1 << 0)

#define XDF_IGNORE_WHITESPACE (1 << 1)
#define XDF_IGNORE_WHITESPACE_CHANGE (1 << 2)
#define XDF_IGNORE_WHITESPACE_AT_EOL (1 << 3)
#define XDF_IGNORE_CR_AT_EOL (1 << 4)
#define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | \
			      XDF_IGNORE_WHITESPACE_CHANGE | \
			      XDF_IGNORE_WHITESPACE_AT_EOL | \
			      XDF_IGNORE_CR_AT_EOL)

#define XDF_IGNORE_BLANK_LINES (1 << 7)

#define XDF_PATIENCE_DIFF (1 << 14)
#define XDF_HISTOGRAM_DIFF (1 << 15)
#define XDF_DIFF_ALGORITHM_MASK (XDF_PATIENCE_DIFF | XDF_HISTOGRAM_DIFF)
#define XDF_DIFF_ALG(x) ((x) & XDF_DIFF_ALGORITHM_MASK)

#define XDF_INDENT_HEURISTIC (1 << 23)

/* xdemitconf_t.flags */
#define XDL_EMIT_FUNCNAMES (1 << 0)
#define XDL_EMIT_FUNCCONTEXT (1 << 2)

#define XDL_MMB_READONLY (1 << 0)

#define XDL_MMF_ATOMIC (1 << 0)

#define XDL_BDOP_INS 1
#define XDL_BDOP_CPY 2
#define XDL_BDOP_INSB 3

/* merge simplification levels */
#define XDL_MERGE_MINIMAL 0
#define XDL_MERGE_EAGER 1
#define XDL_MERGE_ZEALOUS 2
#define XDL_MERGE_ZEALOUS_ALNUM 3

/* merge favor modes */
#define XDL_MERGE_FAVOR_OURS 1
#define XDL_MERGE_FAVOR_THEIRS 2
#define XDL_MERGE_FAVOR_UNION 3

/* merge output styles */
#define XDL_MERGE_DIFF3 1

typedef struct s_mmfile {
	char *ptr;
	long size;
} mmfile_t;

typedef struct s_mmbuffer {
	char *ptr;
	long size;
} mmbuffer_t;

typedef struct s_xpparam {
	unsigned long flags;

	/* See Documentation/diff-options.txt. */
	char **anchors;
	size_t anchors_nr;
} xpparam_t;

typedef struct s_xdemitcb {
	void *priv;
	int (*outf)(void *, mmbuffer_t *, int);
} xdemitcb_t;

typedef long (*find_func_t)(const char *line, long line_len, char *buffer, long buffer_size, void *priv);

typedef int (*xdl_emit_hunk_consume_func_t)(long start_a, long count_a,
					    long start_b, long count_b,
					    void *cb_data);

typedef struct s_xdemitconf {
	long ctxlen;
	long interhunkctxlen;
	unsigned long flags;
	find_func_t find_func;
	void *find_func_priv;
	xdl_emit_hunk_consume_func_t hunk_func;
} xdemitconf_t;

typedef struct s_bdiffparam {
	long bsize;
} bdiffparam_t;


#define xdl_malloc(x) malloc(x)
#define xdl_free(ptr) free(ptr)
#define xdl_realloc(ptr,x) realloc(ptr,x)

void *xdl_mmfile_first(mmfile_t *mmf, long *size);
long xdl_mmfile_size(mmfile_t *mmf);

int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
	     xdemitconf_t const *xecfg, xdemitcb_t *ecb);

typedef struct s_xmparam {
	xpparam_t xpp;
	int marker_size;
	int level;
	int favor;
	int style;
	const char *ancestor;	/* label for orig */
	const char *file1;	/* label for mf1 */
	const char *file2;	/* label for mf2 */
} xmparam_t;

#define DEFAULT_CONFLICT_MARKER_SIZE 7

int xdl_merge(mmfile_t *orig, mmfile_t *mf1, mmfile_t *mf2,
		xmparam_t const *xmp, mmbuffer_t *result);

#ifdef __cplusplus
}
#endif /* #ifdef __cplusplus */

#endif /* #if !defined(XDIFF_H) */