Re: [RFH] shifting xdiff hunks?
On Wed, 12 Apr 2006, Davide Libenzi wrote:
> Yes, this is what GNU diff does. It's a post-process of the edit script. Not
> a problem at all. Till this weekend (included) I'm pretty booked, but I'll do
> that in the following days.
Dang, that was a short weekend. I found a lunch-time hour for this. Would you try to see if this libxdiff-based diff merges on your tree? See also how it looks for you.
- Davide
--- a/xdiffi.c
+++ b/xdiffi.c
@@ -45,6 +45,8 @@
long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
xdalgoenv_t *xenv);
static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2);
+static int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo);
+
@@ -394,6 +396,110 @@
}
+static int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo) {
+ long ix, ixo, ixs, ixref, grpsiz, nrec = xdf->nrec;
+ char *rchg = xdf->rchg, *rchgo = xdfo->rchg;
+ xrecord_t **recs = xdf->recs;
+
+ /*
+ * This is the same of what GNU diff does. Move back and forward
+ * change groups for a consistent and pretty diff output. This also
+ * helps in finding joineable change groups and reduce the diff size.
+ */
+ for (ix = ixo = 0;;) {
+ /*
+ * Find the first changed line in the to-be-compacted file.
+ * We need to keep track of both indexes, so if we find a
+ * changed lines group on the other file, while scanning the
+ * to-be-compacted file, we need to skip it properly. Note
+ * that loops that are testing for changed lines on rchg* do
+ * not need index bounding since the array is prepared with
+ * a zero at position -1 and N.
+ */
+ for (; ix < nrec && !rchg[ix]; ix++)
+ while (rchgo[ixo++]);
+ if (ix == nrec)
+ break;
+
+ /*
+ * Record the start of a changed-group in the to-be-compacted file
+ * and find the end of it, on both to-be-compacted and other file
+ * indexes (ix and ixo).
+ */
+ ixs = ix;
+ for (ix++; rchg[ix]; ix++);
+ for (; rchgo[ixo]; ixo++);
+
+ do {
+ grpsiz = ix - ixs;
+
+ /*
+ * If the line before the current change group, is equal to
+ * the last line of the current change group, shift backward
+ * the group.
+ */
+ while (ixs > 0 && recs[ixs - 1]->ha == recs[ix - 1]->ha &&
+ XDL_RECMATCH(recs[ixs - 1], recs[ix - 1])) {
+ rchg[--ixs] = 1;
+ rchg[--ix] = 0;
+
+ /*
+ * This change might have joined two change groups,
+ * so we try to take this scenario in account by moving
+ * the start index accordingly (and so the other-file
+ * end-of-group index).
+ */
+ for (; rchg[ixs - 1]; ixs--);
+ while (rchgo[--ixo]);
+ }
+
+ /*
+ * Record the end-of-group position in case we are matched
+ * with a group of changes in the other file (that is, the
+ * change record before the enf-of-group index in the other
+ * file is set).
+ */
+ ixref = rchgo[ixo - 1] ? ix: nrec;
+
+ /*
+ * If the first line of the current change group, is equal to
+ * the line next of the current change group, shift forward
+ * the group.
+ */
+ while (ix < nrec && recs[ixs]->ha == recs[ix]->ha &&
+ XDL_RECMATCH(recs[ixs], recs[ix])) {
+ rchg[ixs++] = 0;
+ rchg[ix++] = 1;
+
+ /*
+ * This change might have joined two change groups,
+ * so we try to take this scenario in account by moving
+ * the start index accordingly (and so the other-file
+ * end-of-group index). Keep tracking the reference
+ * index in case we are shifting together with a
+ * corresponding group of changes in the other file.
+ */
+ for (; rchg[ix]; ix++);
+ while (rchgo[++ixo])
+ ixref = ix;
+ }
+ } while (grpsiz != ix - ixs);
+
+ /*
+ * Try to move back the possibly merged group of changes, to match
+ * the recorded postion in the other file.
+ */
+ while (ixref < ix) {
+ rchg[--ixs] = 1;
+ rchg[--ix] = 0;
+ while (rchgo[--ixo]);
+ }
+ }
+
+ return 0;
+}
+
+
int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
xdchange_t *cscr = NULL, *xch;
char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
@@ -439,13 +545,13 @@
return -1;
}
-
- if (xdl_build_script(&xe, &xscr) < 0) {
+ if (xdl_change_compact(&xe.xdf1, &xe.xdf2) < 0 ||
+ xdl_change_compact(&xe.xdf2, &xe.xdf1) < 0 ||
+ xdl_build_script(&xe, &xscr) < 0) {
xdl_free_env(&xe);
return -1;
}
-
if (xscr) {
if (xdl_emit_diff(&xe, xscr, ecb, xecfg) < 0) {
@@ -453,10 +559,8 @@
xdl_free_env(&xe);
return -1;
}
-
xdl_free_script(xscr);
}
-
xdl_free_env(&xe);
return 0;
Junio C Hamano