jssnprintf.c

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/* @(#)jssnprintf.c 1.14 17/08/03 Copyright 1985, 1995-2017 J. Schilling */
/*
 *  Copyright (c) 1985, 1995-2017 J. Schilling
 */
/*
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * See the file CDDL.Schily.txt in this distribution for details.
 * A copy of the CDDL is also available via the Internet at
 * http://www.opensource.org/licenses/cddl1.txt
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file CDDL.Schily.txt from this distribution.
 */
 
#include <schily/mconfig.h>
#include <schily/unistd.h>  /* include <sys/types.h> try to get size_t */
#include <schily/stdio.h>   /* Try again for size_t */
#include <schily/stdlib.h>  /* Try again for size_t */
#include <schily/varargs.h>
#include <schily/standard.h>
#include <schily/schily.h>
 
EXPORT  int js_snprintf __PR((char *, size_t maxcnt, const char *, ...));
 
typedef struct {
    char    *ptr;
    int count;
} *BUF, _BUF;
 
#ifdef  PROTOTYPES
static void
_cput(char c, void *l)
#else
static void
_cput(c, l)
    char    c;
    void    *l;
#endif
{
    register BUF    bp = (BUF)l;
 
    if (--bp->count > 0) {
        *bp->ptr++ = c;
    } else {
        /*
         * Make sure that there will never be a negative overflow.
         */
        bp->count++;
    }
}
 
/* VARARGS2 */
#ifdef  PROTOTYPES
EXPORT int
js_snprintf(char *buf, size_t maxcnt, const char *form, ...)
#else
EXPORT int
js_snprintf(buf, maxcnt, form, va_alist)
    char    *buf;
    unsigned maxcnt;
    char    *form;
    va_dcl
#endif
{
    va_list args;
    int cnt;
    _BUF    bb;
 
    bb.ptr = buf;
    bb.count = maxcnt;
 
#ifdef  PROTOTYPES
    va_start(args, form);
#else
    va_start(args);
#endif
    cnt = format(_cput, &bb, form,  args);
    va_end(args);
    if (maxcnt > 0)
        *(bb.ptr) = '\0';
    if (bb.count < 0)
        return (-1);
 
    return (cnt);
}