path: root/strbuf.c
diff options
authorRené Scharfe <>2007-11-09 00:49:42 (GMT)
committerJunio C Hamano <>2007-11-09 09:30:07 (GMT)
commitcde75e59e1b2d8dd3ba49bc9034692dd06ee3907 (patch)
tree224b5ca0f6d7c0814ada85c5dce4f809d61a1b2b /strbuf.c
parent659c69cfef984e7416decc78841877207e9d5914 (diff)
--pretty=format: on-demand format expansion
Some of the --pretty=format placeholders expansions are expensive to calculate. This is made worse by the current code's use of interpolate(), which requires _all_ placeholders are to be prepared up front. One way to speed this up is to check which placeholders are present in the format string and to prepare only the expansions that are needed. That still leaves the allocation overhead of interpolate(). Another way is to use a callback based approach together with the strbuf library to keep allocations to a minimum and avoid string copies. That's what this patch does. It introduces a new strbuf function, strbuf_expand(). The function takes a format string, list of placeholder strings, a user supplied function 'fn', and an opaque pointer 'context' to tell 'fn' what thingy to operate on. The function 'fn' is expected to accept a strbuf, a parsed placeholder string and the 'context' pointer, and append the interpolated value for the 'context' thingy, according to the format specified by the placeholder. Thanks to Pierre Habouzit for his suggestion to use strchrnul() and the code surrounding its callsite. And thanks to Junio for most of this commit message. :) Here my measurements of most of Paul Mackerras' test cases that highlighted the performance problem (best of three runs): (master) $ time git log --pretty=oneline >/dev/null real 0m0.390s user 0m0.340s sys 0m0.040s (master) $ time git log --pretty=raw >/dev/null real 0m0.434s user 0m0.408s sys 0m0.016s (master) $ time git log --pretty="format:%H {%P} %ct" >/dev/null real 0m1.347s user 0m0.080s sys 0m1.256s (interp_find_active -- Dscho) $ time ./git log --pretty="format:%H {%P} %ct" >/dev/null real 0m0.694s user 0m0.020s sys 0m0.672s (strbuf_expand -- this patch) $ time ./git log --pretty="format:%H {%P} %ct" >/dev/null real 0m0.395s user 0m0.352s sys 0m0.028s Signed-off-by: Rene Scharfe <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'strbuf.c')
1 files changed, 24 insertions, 0 deletions
diff --git a/strbuf.c b/strbuf.c
index f4201e1..536b432 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -129,6 +129,30 @@ void strbuf_addf(struct strbuf *sb, const char *fmt, ...)
strbuf_setlen(sb, sb->len + len);
+void strbuf_expand(struct strbuf *sb, const char *format,
+ const char **placeholders, expand_fn_t fn, void *context)
+ for (;;) {
+ const char *percent, **p;
+ percent = strchrnul(format, '%');
+ strbuf_add(sb, format, percent - format);
+ if (!*percent)
+ break;
+ format = percent + 1;
+ for (p = placeholders; *p; p++) {
+ if (!prefixcmp(format, *p))
+ break;
+ }
+ if (*p) {
+ fn(sb, *p, context);
+ format += strlen(*p);
+ } else
+ strbuf_addch(sb, '%');
+ }
size_t strbuf_fread(struct strbuf *sb, size_t size, FILE *f)
size_t res;