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/*
**	SOPEN - string open
**
**	(c) Copyright Ken Harrenstien 1989
**		for all changes after v.17, 30-May-1988
**	(c) Copyright Ian Macky, SRI International 1986
*/

#include <stdio.h>

#if __STDC__
#define CONST const
#else
#define CONST
#endif

FILE *sopen(s, flags, max_size)
CONST char *s, *flags;
size_t max_size;
{
    char *malloc();
    int c, local_flags = 0;
    FILE *f;

    switch (c = *flags++) {
	case 'r':
	    local_flags |= _SIOF_READ;
	    break;
	case 'w':
	    local_flags |= _SIOF_WRITE;
	    if (*flags && (*flags == '+')) {	/* "w+" means auto-exp str */
		flags++;
		local_flags |= _SIOF_GROWBUF;
	    }
	    break;
	default:  return NULL;
    }
    if (*flags)			/* More stuff left, don't allow it. */
	return NULL;

    if (!(f = _makeFILE())) return NULL;	/* get a FILE descriptor */
/*
 *	if they want us to allocate the string space, then check
 *	the size arg and do it
 */
    if (!s) {
	if (max_size <= 0 || !(s = malloc(max_size))) {
	    _freeFILE(f);
	    return NULL;
	} else f->siopbuf = (char *)s;
    } else f->siopbuf = 0;
/*
 *	now stuff it!
 */
    f->siocp = (char *)s - 1;		/* one before, for pre-inc load */
    f->siolbuf = f->siocnt = max_size;	/* length of buffer */
    f->sioflgs |= local_flags | _SIOF_STR | _SIOF_BUF;
    f->siofd = -1;			/* Ensure no FD there */
    f->siocheck = _SIOF_OPEN;		/* validate block */
    return f;
}