musl/src/stdio/__toread.c

#include <stdio_impl.h>

int __toread(FILE *f)
{
	f->mode |= f->mode-1;
	if (f->wpos > f->buf) f->write(f, 0, 0);
	f->wpos = f->wbase = f->wend = 0;
	if (f->flags & (F_EOF|F_NORD)) {
		if (f->flags & F_NORD) f->flags |= F_ERR;
		return EOF;
	}
	f->rpos = f->rend = f->buf;
	return 0;
}

static const int dummy = 0;
weak_alias(dummy, __towrite_used);

void __seek_on_exit()
{
	if (!__towrite_used) __stdio_exit();
}
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. 2011-03-28 01:14:44 -04:00			`#include <stdio_impl.h>`

			`int __toread(FILE *f)`
			`{`
			`f->mode \|= f->mode-1;`
			`if (f->wpos > f->buf) f->write(f, 0, 0);`
			`f->wpos = f->wbase = f->wend = 0;`
			`if (f->flags & (F_EOF\|F_NORD)) {`
			`if (f->flags & F_NORD) f->flags \|= F_ERR;`
			`return EOF;`
			`}`
			`f->rpos = f->rend = f->buf;`
			`return 0;`
			`}`
stdio: handle file position correctly at program exit for seekable files, posix imposed requirements on the offset of the underlying open file description after a stream is closed. this was correctly handled (as a side effect of the unconditional fflush call) when streams were explicitly closed by fclose, but was not handled correctly at program exit time, where fflush(0) was being used. the weak symbol hackery is to pull in __stdio_exit if either of __toread or __towrite is used, but avoid calling it twice so we don't have to keep extra state. the new __stdio_exit is a streamlined fflush variant that avoids performing any unnecessary operations and which never unlocks the files or open file list, so we can be sure no other threads write new data to a stream's buffer after it's already flushed. 2012-06-19 01:27:26 -04:00
			`static const int dummy = 0;`
			`weak_alias(dummy, __towrite_used);`

			`void __seek_on_exit()`
			`{`
			`if (!__towrite_used) __stdio_exit();`
			`}`