/* Originally released by the musl project (http://www.musl-libc.org/) under the

 * MIT license. Taken and adapted from the file src/stdlib/atoi.c 

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include "parse_num.h"

size_t

parseUInt64(const char *str, size_t size, uint64_t *result) {

    size_t i = 0;

    uint64_t n = 0;

    /* Hex */

    if(size > 2 && str[0] == '0' && (str[1] | 32) == 'x') {

        i = 2;

        for(; i < size; i++) {

            uint8_t c = (uint8_t)str[i] | 32;

            if(c >= '0' && c <= '9')

                c = (uint8_t)(c - '0');

            else if(c >= 'a' && c <='f')

                c = (uint8_t)(c - 'a' + 10);

            else if(c >= 'A' && c <='F')

                c = (uint8_t)(c - 'A' + 10);

            else

                break;

            /* Check for overflow before the shift drops the top bits */

            if(n > (UINT64_MAX >> 4))

                return 0;

            n = (n << 4) | (c & 0xF);

        }

        *result = n;

        return (i > 2) ? i : 0; /* 2 -> No digit was parsed */

    }

    /* Decimal */

    for(; i < size; i++) {

        if(str[i] < '0' || str[i] > '9')

            break;

        uint8_t digit = (uint8_t)(str[i] - '0');

        /* Check for overflow before n*10 + digit wraps around. A wrapped

         * result is not necessarily smaller than the previous value. Both

         * bounds are compile-time constants. */

        if(n > UINT64_MAX / 10 || (n == UINT64_MAX / 10 && digit > UINT64_MAX % 10))

            return 0;

        /* Fast multiplication: n*10 == (n*8) + (n*2) */

        n = (n << 3) + (n << 1) + digit;

    }

    *result = n;

    return i;

}

size_t

parseInt64(const char *str, size_t size, int64_t *result) {

    /* Negative value? */

    size_t i = 0;

    bool neg = false;

    if(*str == '-' || *str == '+') {

        neg = (*str == '-');

        i++;

    }

    /* Parse as unsigned */

    uint64_t n = 0;

    size_t len = parseUInt64(&str[i], size - i, &n);

    if(len == 0)

        return 0;

    /* Check for overflow, adjust and return */

    if(!neg) {

        if(n > 9223372036854775807UL)

            return 0;

        *result = (int64_t)n;

    } else {

        /* n is unsigned, so 9223372036854775808UL == 2^63 fits without

         * overflow. (int64_t)n would also fit for n in [0, 2^63], but

         * the negation -(int64_t)(2^63) is undefined because the result

         * (which is +2^63) cannot be represented. Use the unsigned

         * representation and reinterpret as int64_t instead. */

        if(n > 9223372036854775808UL)

            return 0;

        *result = (n == 9223372036854775808UL)

            ? (int64_t)(-9223372036854775807LL - 1)

            : -(int64_t)n;

    }

    return len + i;

}