fflush.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 * pANS stdio -- fflush
 */
#include "iolib.h"
/*
 * pANS stdio -- data (put here, since loader won't load a separate file)
 */
FILE _IO_stream[]={
/*	fd	flags	state	buf	rp	wp	lp	bufl	unbuf */
	0,	0,	OPEN,	0,	0,	0,	0,	0,	0,
	1,	0,	OPEN,	0,	0,	0,	0,	0,	0,
	2,	0,	OPEN,	0,	0,	0,	0,	0,	0,
};

int _fflush(FILE *f){
	int error, cnt;

	if(f==NULL){
		error=0;
		for(f=_IO_stream;f!=&_IO_stream[FOPEN_MAX];f++)
			if(f->state==WR && _fflush(f)==EOF)
				error=EOF;
		return error;
	}
	if(f->flags&STRING) return EOF;
	switch(f->state){
	default:	/* OPEN RDWR EOF RD */
		return 0;
	case CLOSED:
	case ERR:
		return EOF;
	case WR:
		cnt=(f->flags&LINEBUF?f->lp:f->wp)-f->buf;
		if(cnt && write(f->fd, f->buf, cnt)!=cnt){
			f->state=ERR;
			return EOF;
		}
		f->rp=f->wp=f->buf;
		f->state=RDWR;
		return 0;
	}
}

int fflush(FILE *f)
{
	int r;

	qlock(&_stdiolk);
	r = _fflush(f);
	qunlock(&_stdiolk);
	return r;
}