path: root/src/stdio/fread.c
diff options
authorRich Felker <>2011-03-28 01:14:44 -0400
committerRich Felker <>2011-03-28 01:14:44 -0400
commite3cd6c5c265cd481db6e0c5b529855d99f0bda30 (patch)
tree85d2c586e4ea8e261ed68cc4b1901a1711774441 /src/stdio/fread.c
parentea343364a719add2cd8adf8a50c15bb5f9400dd8 (diff)
major stdio overhaul, using readv/writev, plus other changes
the biggest change in this commit is that stdio now uses readv to fill the caller's buffer and the FILE buffer with a single syscall, and likewise writev to flush the FILE buffer and write out the caller's buffer in a single syscall. making this change required fundamental architectural changes to stdio, so i also made a number of other improvements in the process: - the implementation no longer assumes that further io will fail following errors, and no longer blocks io when the error flag is set (though the latter could easily be changed back if desired) - unbuffered mode is no longer implemented as a one-byte buffer. as a consequence, scanf unreading has to use ungetc, to the unget buffer has been enlarged to hold at least 2 wide characters. - the FILE structure has been rearranged to maintain the locations of the fields that might be used in glibc getc/putc type macros, while shrinking the structure to save some space. - error cases for fflush, fseek, etc. should be more correct. - library-internal macros are used for getc_unlocked and putc_unlocked now, eliminating some ugly code duplication. __uflow and __overflow are no longer used anywhere but these macros. switch to read or write mode is also separated so the code can be better shared, e.g. with ungetc. - lots of other small things.
Diffstat (limited to 'src/stdio/fread.c')
1 files changed, 8 insertions, 15 deletions
diff --git a/src/stdio/fread.c b/src/stdio/fread.c
index 0fa0b2aa..8105fe99 100644
--- a/src/stdio/fread.c
+++ b/src/stdio/fread.c
@@ -12,38 +12,31 @@ size_t fread(void *destv, size_t size, size_t nmemb, FILE *f)
- for (;;) {
+ if (f->rend - f->rpos > 0) {
/* First exhaust the buffer. */
k = MIN(f->rend - f->rpos, l);
memcpy(dest, f->rpos, k);
f->rpos += k;
dest += k;
l -= k;
- /* Stop on EOF or errors */
- if (f->flags & (F_EOF|F_ERR|F_NORD)) goto eof;
- /* Done? Or going unbuffered? */
- if (!l || l > f->buf_size/2) break;
- /* Otherwise, refill & read thru buffer. */
- __underflow(f);
+ }
+ if (!l) {
+ return nmemb;
/* Read the remainder directly */
for (; l; l-=k, dest+=k) {
k = f->read(f, dest, l);
if (k+1<=1) {
- f->flags |= F_EOF | (F_ERR & k);
- goto eof;
+ return (len-l)/size;
return nmemb;
- return (len-l)/size;
weak_alias(fread, fread_unlocked);