xref: /plan9/sys/src/libstdio/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)153e12c5d1SDavid 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 == '+'? ORDWR: OREAD));
343e12c5d1SDavid du Colombier 		break;
353e12c5d1SDavid du Colombier 	case 'w':
36*d9306527SDavid du Colombier 		f->fd=create(name, (*mode == '+'? ORDWR: OWRITE), 0666);
373e12c5d1SDavid du Colombier 		break;
383e12c5d1SDavid du Colombier 	case 'a':
39*d9306527SDavid du Colombier 		m = (*mode == '+'? ORDWR: OWRITE);
403ff48bf5SDavid du Colombier 		f->fd=open(name, m);
413ff48bf5SDavid du Colombier 		if(f->fd<0)
423ff48bf5SDavid du Colombier 			f->fd=create(name, m, 0666);
43*d9306527SDavid du Colombier 		seek(f->fd, 0LL, 2);
443e12c5d1SDavid du Colombier 		break;
453e12c5d1SDavid du Colombier 	}
463ff48bf5SDavid du Colombier 
473ff48bf5SDavid du Colombier 	if(f->fd==-1)
483ff48bf5SDavid du Colombier 		return NULL;
493e12c5d1SDavid du Colombier 	f->flags=(mode[0]=='a')? APPEND : 0;
503e12c5d1SDavid du Colombier 	f->state=OPEN;
513e12c5d1SDavid du Colombier 	f->buf=0;
523e12c5d1SDavid du Colombier 	f->rp=0;
533e12c5d1SDavid du Colombier 	f->wp=0;
543e12c5d1SDavid du Colombier 	f->lp=0;
553e12c5d1SDavid du Colombier 	return f;
563e12c5d1SDavid du Colombier }
57