hypervisor/src/sample/lib/atoi.c

/*
* ========== Copyright Header Begin ==========================================
*
* Hypervisor Software File: atoi.c
*
* Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
*
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*    or without modification, are permitted provided that the following
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*    Neither the name of Sun Microsystems, Inc. or the names of contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
*     This software is provided "AS IS," without a warranty of any kind.
* ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
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* ========== Copyright Header End ============================================
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/*
 * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "@(#)atoi.c     1.3     05/04/26 SMI"

#include <sys/types.h>

extern int isdigit(int c);
extern int isspace(int c);

int
atoi(const char *p)
{
        int n;
        int c, neg = 0;
        unsigned char   *up = (unsigned char *)p;

        if (!isdigit(c = *up)) {
                while (isspace(c))
                        c = *++up;
                switch (c) {
                case '-':
                        neg++;
                        /* FALLTHROUGH */
                case '+':
                        c = *++up;
                }
                if (!isdigit(c))
                        return (0);
        }
        for (n = '0' - c; isdigit(c = *++up); ) {
                n *= 10; /* two steps to avoid unnecessary overflow */
                 n += '0' - c; /* accum neg to avoid surprises at MAX */
        }
        return (neg ? n : -n);
}