xref: /plan9/sys/src/ape/lib/ap/stdio/freopen.c (revision d9306527b4a7229dcf0cf3c58aed36bb9da82854)
13e12c5d1SDavid du Colombier /*
23e12c5d1SDavid du Colombier  * pANS stdio -- freopen
33e12c5d1SDavid du Colombier  */
43e12c5d1SDavid du Colombier #include "iolib.h"
53e12c5d1SDavid du Colombier /*
63e12c5d1SDavid du Colombier  * Open the named file with the given mode, using the given FILE
73e12c5d1SDavid du Colombier  * Legal modes are given below, `additional characters may follow these sequences':
83e12c5d1SDavid du Colombier  * r rb		open to read
93e12c5d1SDavid du Colombier  * w wb		open to write, truncating
103e12c5d1SDavid du Colombier  * a ab		open to write positioned at eof, creating if non-existant
113e12c5d1SDavid du Colombier  * r+ r+b rb+	open to read and write, creating if non-existant
123e12c5d1SDavid du Colombier  * w+ w+b wb+	open to read and write, truncating
133e12c5d1SDavid du Colombier  * a+ a+b ab+	open to read and write, positioned at eof, creating if non-existant.
143e12c5d1SDavid du Colombier  */
freopen(const char * name,const char * mode,FILE * f)153ff48bf5SDavid du Colombier FILE *freopen(const char *name, const char *mode, FILE *f){
163ff48bf5SDavid du Colombier 	int m;
173ff48bf5SDavid du Colombier 
183ff48bf5SDavid du Colombier 	if(f->state!=CLOSED){
193ff48bf5SDavid du Colombier 		fclose(f);
20*d9306527SDavid du Colombier /* premature; fall through and see what happens */
21*d9306527SDavid du Colombier /*		f->state=OPEN; */
223e12c5d1SDavid du Colombier 	}
233ff48bf5SDavid du Colombier 
243ff48bf5SDavid du Colombier 	m = *mode++;
253ff48bf5SDavid du Colombier 	if(m == 0)
263ff48bf5SDavid du Colombier 		return NULL;
273ff48bf5SDavid du Colombier 	if(*mode == 'b')
283ff48bf5SDavid du Colombier 		mode++;
293ff48bf5SDavid du Colombier 	switch(m){
303ff48bf5SDavid du Colombier 	default:
313ff48bf5SDavid du Colombier 		return NULL;
323e12c5d1SDavid du Colombier 	case 'r':
33*d9306527SDavid du Colombier 		f->fd=open(name, (*mode == '+'? O_RDWR: O_RDONLY));
343e12c5d1SDavid du Colombier 		break;
353e12c5d1SDavid du Colombier 	case 'w':
36*d9306527SDavid du Colombier 		f->fd=creat(name, 0666);	/* implicitly O_WRONLY */
37*d9306527SDavid du Colombier 		/* for O_RDWR, have to creat, close, open */
38*d9306527SDavid du Colombier 		if(*mode == '+' && f->fd >= 0) {
39*d9306527SDavid du Colombier 			close(f->fd);
40*d9306527SDavid du Colombier 			f->fd=open(name, O_RDWR);
41*d9306527SDavid du Colombier 		}
423e12c5d1SDavid du Colombier 		break;
433e12c5d1SDavid du Colombier 	case 'a':
44*d9306527SDavid du Colombier 		f->fd=open(name, (*mode == '+'? O_RDWR: O_WRONLY));
45*d9306527SDavid du Colombier 		if(f->fd<0) {
463ff48bf5SDavid du Colombier 			f->fd=creat(name, 0666);
47*d9306527SDavid du Colombier 			/* for O_RDWR, have to creat, close, open */
48*d9306527SDavid du Colombier 			if(*mode == '+' && f->fd >= 0) {
49*d9306527SDavid du Colombier 				close(f->fd);
50*d9306527SDavid du Colombier 				f->fd=open(name, O_RDWR);
51*d9306527SDavid du Colombier 			}
52*d9306527SDavid du Colombier 		}
533e12c5d1SDavid du Colombier 		lseek(f->fd, 0L, 2);
543e12c5d1SDavid du Colombier 		break;
553e12c5d1SDavid du Colombier 	}
563ff48bf5SDavid du Colombier 
573ff48bf5SDavid du Colombier 	if(f->fd==-1)
583ff48bf5SDavid du Colombier 		return NULL;
593e12c5d1SDavid du Colombier 	f->flags=(mode[0]=='a')? APPEND : 0;
603e12c5d1SDavid du Colombier 	f->state=OPEN;
613e12c5d1SDavid du Colombier 	f->buf=0;
623e12c5d1SDavid du Colombier 	f->rp=0;
633e12c5d1SDavid du Colombier 	f->wp=0;
643e12c5d1SDavid du Colombier 	f->lp=0;
653e12c5d1SDavid du Colombier 	return f;
663e12c5d1SDavid du Colombier }
67