source: mainline/uspace/lib/c/generic/strtol.c@ c8afd5a

/*
 * Copyright (c) 2005 Martin Decky
 * Copyright (c) 2008 Jiri Svoboda
 * Copyright (c) 2011 Martin Sucha
 * Copyright (c) 2011 Oleg Romanenko
 * Copyright (c) 2011 Jiri Zarevucky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup libc
 * @{
 */
/** @file
 */

#include <inttypes.h>
#include <stdlib.h>
#include <limits.h>
#include <ctype.h>
#include <assert.h>

// TODO: unit tests

static inline int _digit_value(int c)
{
        if (isdigit(c)) {
                return c - '0';
        } else if (islower(c)) {
                return c - 'a' + 10;
        } else if (isupper(c)) {
                return c - 'A' + 10;
        }
        return INT_MAX;
}

/*
 * FIXME: workaround for GCC "optimizing" the overflow check
 * into soft-emulated 128b multiplication using `__multi3`,
 * which we don't currently implement.
 */
__attribute__((noinline)) static uintmax_t _max_value(int base)
{
        return UINTMAX_MAX / base;
}

static inline uintmax_t _strtoumax(
    const char *restrict nptr, char **restrict endptr, int base,
    bool *restrict sgn)
{
        assert(nptr != NULL);
        assert(sgn != NULL);

        /* Skip leading whitespace. */

        while (isspace(*nptr)) {
                nptr++;
        }

        /* Parse sign, if any. */

        switch (*nptr) {
        case '-':
                *sgn = true;
                nptr++;
                break;
        case '+':
                nptr++;
                break;
        }

        /* Figure out the base. */

        if (base == 0) {
                if (*nptr == '0') {
                        if (tolower(nptr[1]) == 'x') {
                                /* 0x... is hex. */
                                base = 16;
                                nptr += 2;
                        } else {
                                /* 0... is octal. */
                                base = 8;
                        }
                } else {
                        /* Anything else is decimal by default. */
                        base = 10;
                }
        } else if (base == 16) {
                /* Allow hex number to be prefixed with "0x". */
                if (nptr[0] == '0' && tolower(nptr[1]) == 'x') {
                        nptr += 2;
                }
        } else if (base < 0 || base == 1 || base > 36) {
                errno = EINVAL;
                return 0;
        }

        /* Read the value. */

        uintmax_t result = 0;
        uintmax_t max = _max_value(base);
        int digit;

        while (digit = _digit_value(*nptr), digit < base) {

                if (result > max ||
                    __builtin_add_overflow(result * base, digit, &result)) {

                        errno = ERANGE;
                        result = UINTMAX_MAX;
                        break;
                }

                nptr++;
        }

        /* Set endptr. */

        if (endptr != NULL) {
                /*
                 * Move the pointer to the end of the number,
                 * in case it isn't there already.
                 */
                while (_digit_value(*nptr) < base) {
                        nptr++;
                }

                *endptr = (char *) nptr;
        }

        return result;
}

static inline intmax_t _strtosigned(const char *nptr, char **endptr, int base,
    intmax_t min, intmax_t max)
{
        bool sgn = false;
        uintmax_t number = _strtoumax(nptr, endptr, base, &sgn);

        if (number > (uintmax_t) max) {
                if (sgn && (number - 1 == (uintmax_t) max)) {
                        return min;
                }

                errno = ERANGE;
                return (sgn ? min : max);
        }

        return (sgn ? -number : number);
}

static inline uintmax_t _strtounsigned(const char *nptr, char **endptr, int base,
    uintmax_t max)
{
        bool sgn = false;
        uintmax_t number = _strtoumax(nptr, endptr, base, &sgn);

        if (sgn) {
                if (number == 0) {
                        return 0;
                } else {
                        errno = ERANGE;
                        return max;
                }
        }

        if (number > max) {
                errno = ERANGE;
                return max;
        }

        return number;
}

/** Convert initial part of string to long int according to given base.
 * The number may begin with an arbitrary number of whitespaces followed by
 * optional sign (`+' or `-'). If the base is 0 or 16, the prefix `0x' may be
 * inserted and the number will be taken as hexadecimal one. If the base is 0
 * and the number begin with a zero, number will be taken as octal one (as with
 * base 8). Otherwise the base 0 is taken as decimal.
 *
 * @param nptr          Pointer to string.
 * @param[out] endptr   If not NULL, function stores here pointer to the first
 *                      invalid character.
 * @param base          Zero or number between 2 and 36 inclusive.
 * @return              Result of conversion.
 */
long strtol(const char *nptr, char **endptr, int base)
{
        return _strtosigned(nptr, endptr, base, LONG_MIN, LONG_MAX);
}

/** Convert initial part of string to unsigned long according to given base.
 * The number may begin with an arbitrary number of whitespaces followed by
 * optional sign (`+' or `-'). If the base is 0 or 16, the prefix `0x' may be
 * inserted and the number will be taken as hexadecimal one. If the base is 0
 * and the number begin with a zero, number will be taken as octal one (as with
 * base 8). Otherwise the base 0 is taken as decimal.
 *
 * @param nptr          Pointer to string.
 * @param[out] endptr   If not NULL, function stores here pointer to the first
 *                      invalid character
 * @param base          Zero or number between 2 and 36 inclusive.
 * @return              Result of conversion.
 */
unsigned long strtoul(const char *nptr, char **endptr, int base)
{
        return _strtounsigned(nptr, endptr, base, ULONG_MAX);
}

long long strtoll(const char *nptr, char **endptr, int base)
{
        return _strtosigned(nptr, endptr, base, LLONG_MIN, LLONG_MAX);
}

unsigned long long strtoull(const char *nptr, char **endptr, int base)
{
        return _strtounsigned(nptr, endptr, base, ULLONG_MAX);
}

intmax_t strtoimax(const char *nptr, char **endptr, int base)
{
        return _strtosigned(nptr, endptr, base, INTMAX_MIN, INTMAX_MAX);
}

uintmax_t strtoumax(const char *nptr, char **endptr, int base)
{
        return _strtounsigned(nptr, endptr, base, UINTMAX_MAX);
}

int atoi(const char *nptr)
{
        return (int)strtol(nptr, NULL, 10);
}

long atol(const char *nptr)
{
        return strtol(nptr, NULL, 10);
}

long long atoll(const char *nptr)
{
        return strtoll(nptr, NULL, 10);
}

/** @}
 */