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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.
This commit is contained in:
Rich Felker 2011-04-04 16:24:49 -04:00
parent 5600088d38
commit bd57e2b43a
2 changed files with 14 additions and 0 deletions
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1
src/stdio/stderr.c
View File

@ -6,6 +6,7 @@ static FILE f = {
.buf_size = 0, .buf_size = 0,
.fd = 2, .fd = 2,
.flags = F_PERM | F_NORD, .flags = F_PERM | F_NORD,
.lbf = -1,
.write = __stdio_write, .write = __stdio_write,
.seek = __stdio_seek, .seek = __stdio_seek,
.close = __stdio_close, .close = __stdio_close,

13
src/stdio/vfprintf.c
View File

@ -627,13 +627,26 @@ int vfprintf(FILE *f, const char *fmt, va_list ap)
va_list ap2; va_list ap2;
int nl_type[NL_ARGMAX] = {0}; int nl_type[NL_ARGMAX] = {0};
union arg nl_arg[NL_ARGMAX]; union arg nl_arg[NL_ARGMAX];
unsigned char internal_buf[80], *saved_buf = 0;
int ret; int ret;
va_copy(ap2, ap); va_copy(ap2, ap);
if (printf_core(0, fmt, &ap2, nl_arg, nl_type) < 0) return -1; if (printf_core(0, fmt, &ap2, nl_arg, nl_type) < 0) return -1;
FLOCK(f); 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); 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); FUNLOCK(f);
va_end(ap2); va_end(ap2);
return ret; return ret;