source: downloads/tcl8.5.2/compat/strtoul.c @ 47

/* 
 * strtoul.c --
 *
 *      Source code for the "strtoul" library procedure.
 *
 * Copyright (c) 1988 The Regents of the University of California.
 * Copyright (c) 1994 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: strtoul.c,v 1.7 2007/04/16 13:36:34 dkf Exp $
 */

#include "tclInt.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 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(
    CONST 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 CONST char *p;
    register unsigned long int result = 0;
    register unsigned digit;
    int anyDigits = 0;
    int negative=0;
    int overflow=0;

    /*
     * Skip any leading blanks.
     */

    p = string;
    while (isspace(UCHAR(*p))) {
        p += 1;
    }
    if (*p == '-') {
        negative = 1;
        p += 1;
    } else {
        if (*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 == '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[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) {
        unsigned long maxres = ULONG_MAX >> 3;

        for ( ; ; p += 1) {
            digit = *p - '0';
            if (digit > 7) {
                break;
            }
            if (result > maxres) { overflow = 1; }
            result = (result << 3);
            if (digit > (ULONG_MAX - result)) { overflow = 1; }
            result += digit;
            anyDigits = 1;
        }
    } else if (base == 10) {
        unsigned long maxres = ULONG_MAX / 10;

        for ( ; ; p += 1) {
            digit = *p - '0';
            if (digit > 9) {
                break;
            }
            if (result > maxres) { overflow = 1; }
            result *= 10;
            if (digit > (ULONG_MAX - result)) { overflow = 1; }
            result += digit;
            anyDigits = 1;
        }
    } else if (base == 16) {
        unsigned long maxres = ULONG_MAX >> 4;

        for ( ; ; p += 1) {
            digit = *p - '0';
            if (digit > ('z' - '0')) {
                break;
            }
            digit = cvtIn[digit];
            if (digit > 15) {
                break;
            }
            if (result > maxres) { overflow = 1; }
            result = (result << 4);
            if (digit > (ULONG_MAX - result)) { overflow = 1; }
            result += digit;
            anyDigits = 1;
        }
    } else if (base >= 2 && base <= 36) {
        unsigned long maxres = ULONG_MAX / base;

        for ( ; ; p += 1) {
            digit = *p - '0';
            if (digit > ('z' - '0')) {
                break;
            }
            digit = cvtIn[digit];
            if (digit >= ( (unsigned) base )) {
                break;
            }
            if (result > maxres) { overflow = 1; }
            result *= base;
            if (digit > (ULONG_MAX - result)) { overflow = 1; }
            result += digit;
            anyDigits = 1;
        }
    }

    /*
     * See if there were any digits at all.
     */

    if (!anyDigits) {
        p = string;
    }

    if (endPtr != 0) {
        /* unsafe, but required by the strtoul prototype */
        *endPtr = (char *) p;
    }

    if (overflow) {
        errno = ERANGE;
        return ULONG_MAX;
    } 
    if (negative) {
        return -result;
    }
    return result;
}