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author | Rich Felker <dalias@aerifal.cx> | 2011-04-04 16:24:49 -0400 |
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committer | Rich Felker <dalias@aerifal.cx> | 2011-04-04 16:24:49 -0400 |
commit | bd57e2b43a5b56c00a82adbde0e33e5820c81164 (patch) | |
tree | 38cbea7e455183a890bc2293ca1f959816158fa2 /src/stdio/vfprintf.c | |
parent | 5600088d387491bd0af1879aa64e5d388805d8ec (diff) | |
download | musl-bd57e2b43a5b56c00a82adbde0e33e5820c81164.zip musl-bd57e2b43a5b56c00a82adbde0e33e5820c81164.tar.gz musl-bd57e2b43a5b56c00a82adbde0e33e5820c81164.tar.bz2 |
use a local temp buffer for unbuffered streams in vfprintf
this change makes it so most calls to fprintf(stderr, ...) will result
in a single writev syscall, as opposed to roughly 2*N syscalls (and
possibly more) where N is the number of format specifiers. in
principle we could use a much larger buffer, but it's best not to
increase the stack requirements too much. most messages are under 80
chars.
Diffstat (limited to 'src/stdio/vfprintf.c')
-rw-r--r-- | src/stdio/vfprintf.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/stdio/vfprintf.c b/src/stdio/vfprintf.c index 57878c0..8cbfd96 100644 --- a/src/stdio/vfprintf.c +++ b/src/stdio/vfprintf.c @@ -627,13 +627,26 @@ int vfprintf(FILE *f, const char *fmt, va_list ap) va_list ap2; int nl_type[NL_ARGMAX] = {0}; union arg nl_arg[NL_ARGMAX]; + unsigned char internal_buf[80], *saved_buf = 0; int ret; va_copy(ap2, ap); if (printf_core(0, fmt, &ap2, nl_arg, nl_type) < 0) return -1; FLOCK(f); + if (!f->buf_size) { + saved_buf = f->buf; + f->buf = internal_buf; + f->buf_size = sizeof internal_buf; + } ret = printf_core(f, fmt, &ap2, nl_arg, nl_type); + if (saved_buf) { + f->write(f, 0, 0); + if (!f->wpos) ret = -1; + f->buf = saved_buf; + f->buf_size = 0; + f->wpos = f->wbase = f->wend = 0; + } FUNLOCK(f); va_end(ap2); return ret; |