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.

1 files changed, 0 insertions, 38 deletions

diff --git a/src/stdio/__underflow.c b/src/stdio/__underflow.c
deleted file mode 100644
index b769f4e4..00000000
--- a/src/stdio/__underflow.c
+++ /dev/null
@@ -1,38 +0,0 @@
-#include "stdio_impl.h"
-
-int __underflow(FILE *f)
-{
-	ssize_t cnt;
-
-	/* Read from buffer (Do we ever get called when this is true??) */
-	if (f->rpos < f->rstop) return *f->rpos;
-
-	/* Initialize if we're not already reading */
-	if (!f->rstop) {
-		/* Fail immediately if unreadable, eof, or error state. */
-		if (f->flags & (F_EOF|F_ERR|F_NORD)) return EOF;
-
-		/* Set byte orientation -1,0=>-1; 1=>1 */
-		f->mode |= f->mode-1;
-
-		/* Flush any unwritten output; fail on error. */
-		if (f->wpos > f->buf && __oflow(f)) return EOF;
-
-		/* Disallow writes to buffer. */
-		f->wstop = 0;
-	}
-
-	/* Perform the underlying read operation */
-	if ((cnt=f->read(f, f->buf, f->buf_size)) + 1 <= 1) {
-		/* Set flags and leave read mode */
-		f->flags |= F_EOF | (cnt & F_ERR);
-		f->rpos = f->rend = f->rstop = 0;
-		return EOF;
-	}
-
-	/* Setup buffer pointers for reading from buffer */
-	f->rpos = f->buf;
-	f->rend = f->rstop = f->buf + cnt;
-
-	return *f->rpos;
-}