On Fri, 14 Dec 2018 10:49:23 -0700, "Todd C. Miller" wrote:
> After thinking about this a bit more I believe it best to just use
> the existing FILE * and swap in the buffer temporarily. There's
> no need to store the value of the old buffer; since we are unbuffered
> it can only point to _nbuf.
The last diff had a bug. It turns out that __srefill() assumes it
has the entire buffer to use so we need to reset the buffer each
time we call it.
This fixes the problem naddy@ saw with a few of the ports in python
code.
- todd
Index: lib/libc/stdio/fread.c
===================================================================
RCS file: /cvs/src/lib/libc/stdio/fread.c,v
retrieving revision 1.18
diff -u -p -u -r1.18 fread.c
--- lib/libc/stdio/fread.c 16 Dec 2018 03:40:40 -0000 1.18
+++ lib/libc/stdio/fread.c 16 Dec 2018 04:12:32 -0000
@@ -68,6 +68,36 @@ fread(void *buf, size_t size, size_t cou
fp->_r = 0;
total = resid;
p = buf;
+
+ /*
+ * If we're unbuffered we know that the buffer in fp is empty so
+ * we can read directly into buf. This is much faster than a
+ * series of one byte reads into fp->_nbuf.
+ */
+ if ((fp->_flags & __SNBF) != 0 && buf != NULL) {
+ while (resid > 0) {
+ /* set up the buffer */
+ fp->_bf._base = fp->_p = p;
+ fp->_bf._size = resid;
+
+ if (__srefill(fp)) {
+ /* no more input: return partial result */
+ count = (total - resid) / size;
+ break;
+ }
+ p += fp->_r;
+ resid -= fp->_r;
+ }
+
+ /* restore the old buffer (see __smakebuf) */
+ fp->_bf._base = fp->_p = fp->_nbuf;
+ fp->_bf._size = 1;
+ fp->_r = 0;
+
+ FUNLOCKFILE(fp);
+ return (count);
+ }
+
while (resid > (r = fp->_r)) {
(void)memcpy(p, fp->_p, r);
fp->_p += r;
