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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 #include <stddef.h>
     29 #include <stdint.h>
     30 #include <ctype.h>
     31 
     32 static inline int digitval(int ch)
     33 {
     34     unsigned  d;
     35 
     36     d = (unsigned)(ch - '0');
     37     if (d < 10) return (int)d;
     38 
     39     d = (unsigned)(ch - 'a');
     40     if (d < 6) return (int)(d+10);
     41 
     42     d = (unsigned)(ch - 'A');
     43     if (d < 6) return (int)(d+10);
     44 
     45     return -1;
     46 }
     47 
     48 uintmax_t
     49 strntoumax(const char *nptr, char **endptr, int base, size_t n)
     50 {
     51     const unsigned char*  p   = (const unsigned char *)nptr;
     52     const unsigned char*  end = p + n;
     53     int                   minus = 0;
     54     uintmax_t             v = 0;
     55     int                   d;
     56 
     57     /* skip leading space */
     58     while (p < end && isspace(*p))
     59         p++;
     60 
     61     /* Single optional + or - */
     62     if (p < end) {
     63         char c = p[0];
     64         if ( c == '-' || c == '+' ) {
     65             minus = (c == '-');
     66             p++;
     67         }
     68     }
     69 
     70     if ( base == 0 ) {
     71         if ( p+2 < end && p[0] == '0' && (p[1] == 'x' || p[1] == 'X') ) {
     72             p += 2;
     73             base = 16;
     74         } else if ( p+1 < end && p[0] == '0' ) {
     75             p   += 1;
     76             base = 8;
     77         } else {
     78             base = 10;
     79         }
     80     } else if ( base == 16 ) {
     81         if ( p+2 < end && p[0] == '0' && (p[1] == 'x' || p[1] == 'X') ) {
     82             p += 2;
     83         }
     84     }
     85 
     86     while ( p < end && (d = digitval(*p)) >= 0 && d < base ) {
     87         v = v*base + d;
     88         p += 1;
     89     }
     90 
     91     if ( endptr )
     92         *endptr = (char *)p;
     93 
     94     return minus ? -v : v;
     95 }
     96