root/strtoul.c

DEFINITIONS

1. strtoul

/* 
 * strtoul.c --
 *
 *      Source code for the "strtoul" library procedure.
 *
 * Copyright 1988 Regents of the University of California
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#ifndef lint
static char rcsid[] = "$Header: /sprite/src/lib/c/stdlib/RCS/strtoul.c,v 1.2 89/03/22 00:47:33 rab Exp $ SPRITE (Berkeley)";
#endif /* not lint */

#include <sprite.h>
#include <stdlib.h>
#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 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(string, endPtr, base)
    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 = FALSE;

    /*
     * 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 = TRUE;
                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 = TRUE;
        }
    } else if (base == 10) {
        for ( ; ; p += 1) {
            digit = *p - '0';
            if (digit > 9) {
                break;
            }
            result = (10*result) + digit;
            anyDigits = TRUE;
        }
    } 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 = TRUE;
        }
    } else {
        for ( ; ; p += 1) {
            digit = *p - '0';
            if (digit > ('z' - '0')) {
                break;
            }
            digit = cvtIn[digit];
            if (digit >= base) {
                break;
            }
            result = result*base + digit;
            anyDigits = TRUE;
        }
    }

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

    if (!anyDigits) {
        p = string;
    }

    if (endPtr != NULL) {
        *endPtr = p;
    }

    return result;
}