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strtoul.c

/* 
 * strtoul.c --
 *
 *    Source code for the "strtoul" library procedure.
 *
 * Copyright (c) 1988 The Regents of the University of California.
 * All rights reserved.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and its documentation for any purpose, provided that the
 * above copyright notice and the following two paragraphs appear in
 * all copies of this software.
 * 
 * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
 * CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 */
static const char rcsid[] = "$Header: strtoul.c,v 1.2 96/03/16 13:13:59 van Exp $ SPRITE (Berkeley)";

#include <ctype.h>

/*
 * The table below is used to convert from ASCII digits to a
 * numerical equivalent.  It maps from '0' through 'z' to integers
 * (100 for non-digit characters).
 */

static const char cvtIn[] = {
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9,         /* '0' - '9' */
    100, 100, 100, 100, 100, 100, 100,          /* punctuation */
    10, 11, 12, 13, 14, 15, 16, 17, 18, 19,     /* 'A' - 'Z' */
    20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
    30, 31, 32, 33, 34, 35,
    100, 100, 100, 100, 100, 100,         /* punctuation */
    10, 11, 12, 13, 14, 15, 16, 17, 18, 19,     /* 'a' - 'z' */
    20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
    30, 31, 32, 33, 34, 35};

/*
 *----------------------------------------------------------------------
 *
 * strtoul --
 *
 *    Convert an ASCII string into an integer.
 *
 * Results:
 *    The return value is the integer equivalent of string.  If endPtr
 *    is non-NULL, then *endPtr is filled in with the character
 *    after the last one that was part of the integer.  If string
 *    doesn't contain a valid integer value, then zero is returned
 *    and *endPtr is set to string.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

unsigned long int
strtoul(
    char *string,       /* String of ASCII digits, possibly
                         * preceded by white space.  For bases
                         * greater than 10, either lower- or
                         * upper-case digits may be used.
                         */
    char **endPtr,            /* Where to store address of terminating
                         * character, or NULL. */
    int base                  /* Base for conversion.  Must be less
                         * than 37.  If 0, then the base is chosen
                         * from the leading characters of string:
                         * "0x" means hex, "0" means octal, anything
                         * else means decimal.
                         */
)
{
    register char *p;
    register unsigned long int result = 0;
    register unsigned digit;
    int anyDigits = 0;

    /*
     * Skip any leading blanks.
     */
    p = string;
    while (isspace(*p)) {
      p += 1;
    }

    /*
     * If no base was provided, pick one from the leading characters
     * of the string.
     */
    if (base == 0)
    {
      if (*p == '0') {
          p += 1;
          if (*p == 'x') {
            p += 1;
            base = 16;
          } else {

            /*
             * Must set anyDigits here, otherwise "0" produces a
             * "no digits" error.
             */
            anyDigits = 1;
            base = 8;
          }
      }
      else base = 10;
    } else if (base == 16) {

      /*
       * Skip a leading "0x" from hex numbers.
       */
      if ((p[0] == '0') && (p[1] == 'x')) {
          p += 2;
      }
    }

    /*
     * Sorry this code is so messy, but speed seems important.  Do
     * different things for base 8, 10, 16, and other.
     */
    if (base == 8) {
      for ( ; ; p += 1) {
          digit = *p - '0';
          if (digit > 7) {
            break;
          }
          result = (result << 3) + digit;
          anyDigits = 1;
      }
    } else if (base == 10) {
      for ( ; ; p += 1) {
          digit = *p - '0';
          if (digit > 9) {
            break;
          }
          result = (10*result) + digit;
          anyDigits = 1;
      }
    } else if (base == 16) {
      for ( ; ; p += 1) {
          digit = *p - '0';
          if (digit > ('z' - '0')) {
            break;
          }
          digit = cvtIn[digit];
          if (digit > 15) {
            break;
          }
          result = (result << 4) + digit;
          anyDigits = 1;
      }
    } else {
      for ( ; ; p += 1) {
          digit = *p - '0';
          if (digit > ('z' - '0')) {
            break;
          }
          digit = cvtIn[digit];
          if (digit >= base) {
            break;
          }
          result = result*base + digit;
          anyDigits = 1;
      }
    }

    /*
     * See if there were any digits at all.
     */
    if (!anyDigits) {
      p = string;
    }
    if (endPtr != 0) {
      *endPtr = p;
    }
    return result;
}

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