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authorTheodore Ts'o <tytso@mit.edu>2007-06-29 17:40:46 (GMT)
committerJunio C Hamano <gitster@pobox.com>2007-07-01 03:16:12 (GMT)
commit06f59e9f5daa06fc4bd51cf4c508b3edd3ed514a (patch)
tree589caae1830bf51eb10f1022cdb0a8f5fa97ba07 /write_or_die.c
parentee36856d8c8c1f8d53650a70d8f61561fb65ba38 (diff)
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Don't fflush(stdout) when it's not helpful
This patch arose from a discussion started by Jim Meyering's patch whose intention was to provide better diagnostics for failed writes. Linus proposed a better way to do things, which also had the added benefit that adding a fflush() to git-log-* operations and incremental git-blame operations could improve interactive respose time feel, at the cost of making things a bit slower when we aren't piping the output to a downstream program. This patch skips the fflush() calls when stdout is a regular file, or if the environment variable GIT_FLUSH is set to "0". This latter can speed up a command such as: GIT_FLUSH=0 strace -c -f -e write time git-rev-list HEAD | wc -l a tiny amount. Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'write_or_die.c')
-rw-r--r--write_or_die.c40
1 files changed, 40 insertions, 0 deletions
diff --git a/write_or_die.c b/write_or_die.c
index 5c4bc85..e125e11 100644
--- a/write_or_die.c
+++ b/write_or_die.c
@@ -1,5 +1,45 @@
#include "cache.h"
+/*
+ * Some cases use stdio, but want to flush after the write
+ * to get error handling (and to get better interactive
+ * behaviour - not buffering excessively).
+ *
+ * Of course, if the flush happened within the write itself,
+ * we've already lost the error code, and cannot report it any
+ * more. So we just ignore that case instead (and hope we get
+ * the right error code on the flush).
+ *
+ * If the file handle is stdout, and stdout is a file, then skip the
+ * flush entirely since it's not needed.
+ */
+void maybe_flush_or_die(FILE *f, const char *desc)
+{
+ static int skip_stdout_flush = -1;
+ struct stat st;
+ char *cp;
+
+ if (f == stdout) {
+ if (skip_stdout_flush < 0) {
+ cp = getenv("GIT_FLUSH");
+ if (cp)
+ skip_stdout_flush = (atoi(cp) == 0);
+ else if ((fstat(fileno(stdout), &st) == 0) &&
+ S_ISREG(st.st_mode))
+ skip_stdout_flush = 1;
+ else
+ skip_stdout_flush = 0;
+ }
+ if (skip_stdout_flush && !ferror(f))
+ return;
+ }
+ if (fflush(f)) {
+ if (errno == EPIPE)
+ exit(0);
+ die("write failure on %s: %s", desc, strerror(errno));
+ }
+}
+
int read_in_full(int fd, void *buf, size_t count)
{
char *p = buf;