D2634: [DRAFT] xdiff: avoid hashing trimmed lines

[quark (Jun Wu)]

quark created this revision.
Herald added a subscriber: mercurial-devel.
Herald added a reviewer: hg-reviewers.

REVISION SUMMARY
  Things are a bit faster now:
  
    hg perfbdiff --count 3000 --blocks --xdiff 
.hg/store/data/mercurial/commands.py.i 1
    # before
    ! wall 1.510821 comb 1.500000 user 1.500000 sys 0.000000 (best of 6)
    # after
    ! wall 1.025628 comb 1.020000 user 1.020000 sys 0.000000 (best of 8)

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2634

AFFECTED FILES
  mercurial/thirdparty/xdiff/xprepare.c
  mercurial/thirdparty/xdiff/xutils.c
  mercurial/thirdparty/xdiff/xutils.h

CHANGE DETAILS

diff --git a/mercurial/thirdparty/xdiff/xutils.h 
b/mercurial/thirdparty/xdiff/xutils.h
--- a/mercurial/thirdparty/xdiff/xutils.h
+++ b/mercurial/thirdparty/xdiff/xutils.h
@@ -34,6 +34,7 @@
 long xdl_guess_lines(mmfile_t *mf, long sample);
 int xdl_blankline(const char *line, long size, long flags);
 int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags);
+void xdl_next_record(char const **data, char const *top);
 unsigned long xdl_hash_record(char const **data, char const *top, long flags);
 unsigned int xdl_hashbits(unsigned int size);
 int xdl_num_out(char *out, long val);
diff --git a/mercurial/thirdparty/xdiff/xutils.c 
b/mercurial/thirdparty/xdiff/xutils.c
--- a/mercurial/thirdparty/xdiff/xutils.c
+++ b/mercurial/thirdparty/xdiff/xutils.c
@@ -298,6 +298,15 @@
        return ha;
 }
 
+inline void xdl_next_record(char const **data, char const *top) {
+       char const *next = memchr(*data, '\n', top - *data);
+       if (next) {
+               *data = next + 1;
+       } else {
+               *data = top;
+       }
+}
+
 unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
        unsigned long ha = 5381;
        char const *ptr = *data;
diff --git a/mercurial/thirdparty/xdiff/xprepare.c 
b/mercurial/thirdparty/xdiff/xprepare.c
--- a/mercurial/thirdparty/xdiff/xprepare.c
+++ b/mercurial/thirdparty/xdiff/xprepare.c
@@ -181,7 +181,7 @@
        if ((cur = blk = xdl_mmfile_first(mf, &bsize)) != NULL) {
                for (top = blk + bsize; cur < top; ) {
                        prev = cur;
-                       hav = xdl_hash_record(&cur, top, xpp->flags);
+                       xdl_next_record(&cur, top);
                        if (nrec >= narec) {
                                narec *= 2;
                                if (!(rrecs = (xrecord_t **) xdl_realloc(recs, 
narec * sizeof(xrecord_t *))))
@@ -192,7 +192,7 @@
                                goto abort;
                        crec->ptr = prev;
                        crec->size = (long) (cur - prev);
-                       crec->ha = hav;
+                       crec->ha = 0;
                        recs[nrec++] = crec;
                }
        }
@@ -243,7 +243,7 @@
 
        unsigned int hbits;
        long hsize;
-       long i;
+       long i, j;
        long start = xdf->dstart - reserved;
        long end = xdf->dend + reserved;
 
@@ -261,6 +261,16 @@
        memset(rhash, 0, hsize * sizeof(xrecord_t *));
 
        for (i = start; i <= end; i++) {
+               {
+                       unsigned long ha = 5381;
+                       char const *ptr = xdf->recs[i]->ptr;
+
+                       for (j = 0; j < xdf->recs[i]->size; ++j) {
+                               ha += (ha << 5);
+                               ha ^= (unsigned long)ptr[j];
+                       }
+                       xdf->recs[i]->ha = ha;
+               }
                if (xdl_classify_record(pass, cf, rhash, hbits, xdf->recs[i]) < 
0)
                        goto abort;
        }



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Cc: mercurial-devel
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