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authorEzekiel Newren <ezekielnewren@gmail.com>2025-09-26 22:41:58 +0000
committerJunio C Hamano <gitster@pobox.com>2025-10-03 10:19:40 -0700
commite385e1b7d2d7f531a0006131e7f1d974de351df5 (patch)
tree17a83cb37af1ffcea91a5dd7272a1761733a7948 /xdiff
parentb7de64a6d6f58953a0c1dc7ff34f7080b3e38b37 (diff)
downloadgit-e385e1b7d2d7f531a0006131e7f1d974de351df5.tar.gz
xdiff: add macros DISCARD(0), KEEP(1), INVESTIGATE(2) in xprepare.c
This commit is refactor-only; no behavior is changed. A future commit will use bool literals for changed[i]. The functions xdl_clean_mmatch() and xdl_cleanup_records() will be cleaned up more in a future patch series. The changes to xdl_cleanup_records(), in this patch, are just to make it clear why `char rchg` is refactored to `bool changed`. Rename dis* to action* and replace literal numericals with macros. The old names came from when dis* (which I think was short for discard) was treated like a boolean, but over time it grew into a ternary state machine. The result was confusing because dis* and rchg* both used 0/1 values with different meanings. The new names and macros make the states explicit. nm is short for number of matches, and mlim is a heuristic limit: nm == 0 -> action[i] = DISCARD -> changed[i] = true 0 < nm < mlim -> action[i] = KEEP -> changed[i] = false nm >= mlim -> action[i] = INVESTIGATE -> changed[i] = xdl_clean_mmatch() When need_min is true, only DISCARD and KEEP occur because the limit is effectively infinite. Best-viewed-with: --color-words Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'xdiff')
-rw-r--r--xdiff/xprepare.c106
1 files changed, 69 insertions, 37 deletions
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index b9b19c36de..55e3b50ce6 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -29,6 +29,9 @@
#define XDL_GUESS_NLINES1 256
#define XDL_GUESS_NLINES2 20
+#define DISCARD 0
+#define KEEP 1
+#define INVESTIGATE 2
typedef struct s_xdlclass {
struct s_xdlclass *next;
@@ -190,15 +193,15 @@ void xdl_free_env(xdfenv_t *xe) {
}
-static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
+static bool xdl_clean_mmatch(uint8_t const *action, long i, long s, long e) {
long r, rdis0, rpdis0, rdis1, rpdis1;
/*
- * Limits the window the is examined during the similar-lines
- * scan. The loops below stops when dis[i - r] == 1 (line that
- * has no match), but there are corner cases where the loop
- * proceed all the way to the extremities by causing huge
- * performance penalties in case of big files.
+ * Limits the window that is examined during the similar-lines
+ * scan. The loops below stops when action[i - r] == KEEP
+ * (line that has no match), but there are corner cases where
+ * the loop proceed all the way to the extremities by causing
+ * huge performance penalties in case of big files.
*/
if (i - s > XDL_SIMSCAN_WINDOW)
s = i - XDL_SIMSCAN_WINDOW;
@@ -207,40 +210,47 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
/*
* Scans the lines before 'i' to find a run of lines that either
- * have no match (dis[j] == 0) or have multiple matches (dis[j] > 1).
- * Note that we always call this function with dis[i] > 1, so the
- * current line (i) is already a multimatch line.
+ * have no match (action[j] == DISCARD) or have multiple matches
+ * (action[j] == INVESTIGATE). Note that we always call this
+ * function with action[i] == INVESTIGATE, so the current line
+ * (i) is already a multimatch line.
*/
for (r = 1, rdis0 = 0, rpdis0 = 1; (i - r) >= s; r++) {
- if (!dis[i - r])
+ if (action[i - r] == DISCARD)
rdis0++;
- else if (dis[i - r] == 2)
+ else if (action[i - r] == INVESTIGATE)
rpdis0++;
- else
+ else if (action[i - r] == KEEP)
break;
+ else
+ BUG("Illegal value for action[i - r]");
}
/*
- * If the run before the line 'i' found only multimatch lines, we
- * return 0 and hence we don't make the current line (i) discarded.
- * We want to discard multimatch lines only when they appear in the
- * middle of runs with nomatch lines (dis[j] == 0).
+ * If the run before the line 'i' found only multimatch lines,
+ * we return false and hence we don't make the current line (i)
+ * discarded. We want to discard multimatch lines only when
+ * they appear in the middle of runs with nomatch lines
+ * (action[j] == DISCARD).
*/
if (rdis0 == 0)
return 0;
for (r = 1, rdis1 = 0, rpdis1 = 1; (i + r) <= e; r++) {
- if (!dis[i + r])
+ if (action[i + r] == DISCARD)
rdis1++;
- else if (dis[i + r] == 2)
+ else if (action[i + r] == INVESTIGATE)
rpdis1++;
- else
+ else if (action[i + r] == KEEP)
break;
+ else
+ BUG("Illegal value for action[i + r]");
}
/*
- * If the run after the line 'i' found only multimatch lines, we
- * return 0 and hence we don't make the current line (i) discarded.
+ * If the run after the line 'i' found only multimatch lines,
+ * we return false and hence we don't make the current line (i)
+ * discarded.
*/
if (rdis1 == 0)
- return 0;
+ return false;
rdis1 += rdis0;
rpdis1 += rpdis0;
@@ -251,26 +261,38 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
/*
* Try to reduce the problem complexity, discard records that have no
* matches on the other file. Also, lines that have multiple matches
- * might be potentially discarded if they happear in a run of discardable.
+ * might be potentially discarded if they appear in a run of discardable.
*/
static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {
long i, nm, nreff, mlim;
xrecord_t *recs;
xdlclass_t *rcrec;
- char *dis, *dis1, *dis2;
- int need_min = !!(cf->flags & XDF_NEED_MINIMAL);
+ uint8_t *action1 = NULL, *action2 = NULL;
+ bool need_min = !!(cf->flags & XDF_NEED_MINIMAL);
+ int ret = 0;
- if (!XDL_CALLOC_ARRAY(dis, xdf1->nrec + xdf2->nrec + 2))
- return -1;
- dis1 = dis;
- dis2 = dis1 + xdf1->nrec + 1;
+ /*
+ * Create temporary arrays that will help us decide if
+ * changed[i] should remain 0 or become 1.
+ */
+ if (!XDL_CALLOC_ARRAY(action1, xdf1->nrec + 1)) {
+ ret = -1;
+ goto cleanup;
+ }
+ if (!XDL_CALLOC_ARRAY(action2, xdf2->nrec + 1)) {
+ ret = -1;
+ goto cleanup;
+ }
+ /*
+ * Initialize temporary arrays with DISCARD, KEEP, or INVESTIGATE.
+ */
if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)
mlim = XDL_MAX_EQLIMIT;
for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {
rcrec = cf->rcrecs[recs->ha];
nm = rcrec ? rcrec->len2 : 0;
- dis1[i] = (nm == 0) ? 0: (nm >= mlim && !need_min) ? 2: 1;
+ action1[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP;
}
if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)
@@ -278,32 +300,42 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {
rcrec = cf->rcrecs[recs->ha];
nm = rcrec ? rcrec->len1 : 0;
- dis2[i] = (nm == 0) ? 0: (nm >= mlim && !need_min) ? 2: 1;
+ action2[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP;
}
+ /*
+ * Use temporary arrays to decide if changed[i] should remain
+ * 0 or become 1.
+ */
for (nreff = 0, i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];
i <= xdf1->dend; i++, recs++) {
- if (dis1[i] == 1 ||
- (dis1[i] == 2 && !xdl_clean_mmatch(dis1, i, xdf1->dstart, xdf1->dend))) {
+ if (action1[i] == KEEP ||
+ (action1[i] == INVESTIGATE && !xdl_clean_mmatch(action1, i, xdf1->dstart, xdf1->dend))) {
xdf1->rindex[nreff++] = i;
+ /* changed[i] remains 0, i.e. keep */
} else
xdf1->changed[i] = 1;
+ /* i.e. discard */
}
xdf1->nreff = nreff;
for (nreff = 0, i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart];
i <= xdf2->dend; i++, recs++) {
- if (dis2[i] == 1 ||
- (dis2[i] == 2 && !xdl_clean_mmatch(dis2, i, xdf2->dstart, xdf2->dend))) {
+ if (action2[i] == KEEP ||
+ (action2[i] == INVESTIGATE && !xdl_clean_mmatch(action2, i, xdf2->dstart, xdf2->dend))) {
xdf2->rindex[nreff++] = i;
+ /* changed[i] remains 0, i.e. keep */
} else
xdf2->changed[i] = 1;
+ /* i.e. discard */
}
xdf2->nreff = nreff;
- xdl_free(dis);
+cleanup:
+ xdl_free(action1);
+ xdl_free(action2);
- return 0;
+ return ret;
}
generated by cgit 1.2.3-korg (git 2.43.0) at 2025-12-07 11:58:22 +0000