summaryrefslogtreecommitdiff
path: root/strbuf.c
diff options
context:
space:
mode:
authorJeff King <peff@peff.net>2015-04-16 05:01:38 -0400
committerJunio C Hamano <gitster@pobox.com>2015-04-16 08:15:05 -0700
commit0cc30e0e842a25846e76e09f62a1d425a25ee556 (patch)
treeaa967acf53f4e40271e0b36ab2d188d16eb6973e /strbuf.c
parentf80c153bea4e0ea86f5b6d32e77df0b69501ee18 (diff)
downloadgit-0cc30e0e842a25846e76e09f62a1d425a25ee556.tar.gz
strbuf_getwholeline: use getdelim if it is available
We spend a lot of time in strbuf_getwholeline in a tight loop reading characters from a stdio handle into a buffer. The libc getdelim() function can do this for us with less overhead. It's in POSIX.1-2008, and was a GNU extension before that. Therefore we can't rely on it, but can fall back to the existing getc loop when it is not available. The HAVE_GETDELIM knob is turned on automatically for Linux, where we have glibc. We don't need to set any new feature-test macros, because we already define _GNU_SOURCE. Other systems that implement getdelim may need to other macros (probably _POSIX_C_SOURCE >= 200809L), but we can address that along with setting the Makefile knob after testing the feature on those systems. Running "git rev-parse refs/heads/does-not-exist" on a repo with an extremely large (1.6GB) packed-refs file went from (best-of-5): real 0m8.601s user 0m8.084s sys 0m0.524s to: real 0m6.768s user 0m6.340s sys 0m0.432s for a wall-clock speedup of 21%. Based on a patch from Rasmus Villemoes <rv@rasmusvillemoes.dk>. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'strbuf.c')
-rw-r--r--strbuf.c42
1 files changed, 42 insertions, 0 deletions
diff --git a/strbuf.c b/strbuf.c
index 921619ea68..0d4f4e54ec 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -435,6 +435,47 @@ int strbuf_getcwd(struct strbuf *sb)
return -1;
}
+#ifdef HAVE_GETDELIM
+int strbuf_getwholeline(struct strbuf *sb, FILE *fp, int term)
+{
+ ssize_t r;
+
+ if (feof(fp))
+ return EOF;
+
+ strbuf_reset(sb);
+
+ /* Translate slopbuf to NULL, as we cannot call realloc on it */
+ if (!sb->alloc)
+ sb->buf = NULL;
+ r = getdelim(&sb->buf, &sb->alloc, term, fp);
+
+ if (r > 0) {
+ sb->len = r;
+ return 0;
+ }
+ assert(r == -1);
+
+ /*
+ * Normally we would have called xrealloc, which will try to free
+ * memory and recover. But we have no way to tell getdelim() to do so.
+ * Worse, we cannot try to recover ENOMEM ourselves, because we have
+ * no idea how many bytes were read by getdelim.
+ *
+ * Dying here is reasonable. It mirrors what xrealloc would do on
+ * catastrophic memory failure. We skip the opportunity to free pack
+ * memory and retry, but that's unlikely to help for a malloc small
+ * enough to hold a single line of input, anyway.
+ */
+ if (errno == ENOMEM)
+ die("Out of memory, getdelim failed");
+
+ /* Restore slopbuf that we moved out of the way before */
+ if (!sb->buf)
+ strbuf_init(sb, 0);
+ return EOF;
+}
+#else
int strbuf_getwholeline(struct strbuf *sb, FILE *fp, int term)
{
int ch;
@@ -458,6 +499,7 @@ int strbuf_getwholeline(struct strbuf *sb, FILE *fp, int term)
sb->buf[sb->len] = '\0';
return 0;
}
+#endif
int strbuf_getline(struct strbuf *sb, FILE *fp, int term)
{