ref: e72da62915b09d5673b0c0179ba8dfe045aeb8c3
dir: /sys/src/libstdio/freopen.c/
/*
* pANS stdio -- freopen
*/
#include "iolib.h"
/*
* Open the named file with the given mode, using the given FILE
* Legal modes are given below, `additional characters may follow these sequences':
* r rb open to read
* w wb open to write, truncating
* a ab open to write positioned at eof, creating if non-existant
* r+ r+b rb+ open to read and write, creating if non-existant
* w+ w+b wb+ open to read and write, truncating
* a+ a+b ab+ open to read and write, positioned at eof, creating if non-existant.
*/
FILE *freopen(const char *name, const char *mode, FILE *f){
int m;
if(f->state!=CLOSED){
fclose(f);
/* premature; fall through and see what happens */
/* f->state=OPEN; */
}
m = *mode++;
if(m == 0)
return NULL;
if(*mode == 'b')
mode++;
switch(m){
default:
return NULL;
case 'r':
f->fd=open(name, (*mode == '+'? ORDWR: OREAD));
break;
case 'w':
f->fd=create(name, (*mode == '+'? ORDWR: OWRITE), 0666);
break;
case 'a':
m = (*mode == '+'? ORDWR: OWRITE);
f->fd=open(name, m);
if(f->fd<0)
f->fd=create(name, m, 0666);
seek(f->fd, 0LL, 2);
break;
}
if(f->fd==-1)
return NULL;
f->flags=(mode[0]=='a')? APPEND : 0;
f->state=OPEN;
f->buf=0;
f->rp=0;
f->wp=0;
f->lp=0;
return f;
}