diff: avoid repeated scanning while looking for funcname
For each hunk, xdl_find_func searches the preimage for a function name until the beginning of the file. If the file does not contain any function names, this search has complexity O(n^2) in the number of hunks n. Instead, inline xdl_find_func() and keep track of up to which line we have scanned already and the contents of the last funcname line that we have found. Noticed and a different approach proposed by Clemens Buchacher. This alternative solution was done by René Scharfe. Signed-off-by: Junio C Hamano <gitster@pobox.com>
René Scharfe committed
Sep 26, 2010 at 18:26 UTC
c099789bb01b810e40f9cfaa5c842ed568110fc8
1 file changed
+14
-24
xdiff/xemit.c
+14
-24
@@ -85,27 +85,6 @@ static long def_ff(const char *rec, long len, char *buf, long sz, void *priv)
85
return -1;
86
}
87
88
-static void xdl_find_func(xdfile_t *xf, long i, char *buf, long sz, long *ll,
89
- find_func_t ff, void *ff_priv) {
90
-
91
- /*
92
- * Be quite stupid about this for now. Find a line in the old file
93
- * before the start of the hunk (and context) which starts with a
94
- * plausible character.
95
- */
96
-
97
- const char *rec;
98
- long len;
99
-
100
- while (i-- > 0) {
101
- len = xdl_get_rec(xf, i, &rec);
102
- if ((*ll = ff(rec, len, buf, sz, ff_priv)) >= 0)
103
- return;
104
- }
105
- *ll = 0;
106
-}
107
-
108
-
88
static int xdl_emit_common(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
89
xdemitconf_t const *xecfg) {
90
xdfile_t *xdf = &xe->xdf1;
@@ -127,6 +106,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
106
xdchange_t *xch, *xche;
107
char funcbuf[80];
108
long funclen = 0;
109
+ long funclineprev = -1;
110
find_func_t ff = xecfg->find_func ? xecfg->find_func : def_ff;
111
112
if (xecfg->flags & XDL_EMIT_COMMON)
@@ -150,9 +130,19 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
130
*/
131
132
if (xecfg->flags & XDL_EMIT_FUNCNAMES) {
153
- xdl_find_func(&xe->xdf1, s1, funcbuf,
154
- sizeof(funcbuf), &funclen,
155
- ff, xecfg->find_func_priv);
133
+ long l;
134
+ for (l = s1 - 1; l >= 0 && l > funclineprev; l--) {
135
+ const char *rec;
136
+ long reclen = xdl_get_rec(&xe->xdf1, l, &rec);
137
+ long newfunclen = ff(rec, reclen, funcbuf,
138
+ sizeof(funcbuf),
139
+ xecfg->find_func_priv);
140
+ if (newfunclen >= 0) {
141
+ funclen = newfunclen;
142
+ break;
143
+ }
144
+ }
145
+ funclineprev = s1 - 1;
146
}
147
if (xdl_emit_hunk_hdr(s1 + 1, e1 - s1, s2 + 1, e2 - s2,
148
funcbuf, funclen, ecb) < 0)