kernel/lib/libc/atoi.c

// Copyright 2016 The Fuchsia Authors
// Copyright (c) 2008 Travis Geiselbrecht
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT


#include <stdlib.h>
#include <ctype.h>
#include <errno.h>

#define LONG_IS_INT 1

static int hexval(char c)
{
    if (c >= '0' && c <= '9')
        return c - '0';
    else if (c >= 'a' && c <= 'f')
        return c - 'a' + 10;
    else if (c >= 'A' && c <= 'F')
        return c - 'A' + 10;

    return 0;
}

int atoi(const char *num)
{
#if !LONG_IS_INT
    // XXX fail
#else
    return atol(num);
#endif
}

unsigned int atoui(const char *num)
{
#if !LONG_IS_INT
    // XXX fail
#else
    return atoul(num);
#endif
}

long atol(const char *num)
{
    long value = 0;
    int neg = 0;

    if (num[0] == '0' && num[1] == 'x') {
        // hex
        num += 2;
        while (*num && isxdigit(*num))
            value = value * 16 + hexval(*num++);
    } else {
        // decimal
        if (num[0] == '-') {
            neg = 1;
            num++;
        }
        while (*num && isdigit(*num))
            value = value * 10 + *num++  - '0';
    }

    if (neg)
        value = -value;

    return value;
}

unsigned long atoul(const char *num)
{
    unsigned long value = 0;
    if (num[0] == '0' && num[1] == 'x') {
        // hex
        num += 2;
        while (*num && isxdigit(*num))
            value = value * 16 + hexval(*num++);
    } else {
        // decimal
        while (*num && isdigit(*num))
            value = value * 10 + *num++  - '0';
    }

    return value;
}

unsigned long long atoull(const char *num)
{
    unsigned long long value = 0;
    if (num[0] == '0' && num[1] == 'x') {
        // hex
        num += 2;
        while (*num && isxdigit(*num))
            value = value * 16 + hexval(*num++);
    } else {
        // decimal
        while (*num && isdigit(*num))
            value = value * 10 + *num++  - '0';
    }

    return value;
}

unsigned long strtoul(const char *nptr, char **endptr, int base)
{
    int neg = 0;
    unsigned long ret = 0;

    if (base < 0 || base == 1 || base > 36) {
        errno = EINVAL;
        return 0;
    }

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

    if (*nptr == '+') {
        nptr++;
    } else if (*nptr == '-') {
        neg = 1;
        nptr++;
    }

    if ((base == 0 || base == 16) && nptr[0] == '0' && nptr[1] == 'x') {
        base = 16;
        nptr += 2;
    } else if (base == 0 && nptr[0] == '0') {
        base = 8;
        nptr++;
    } else if (base == 0) {
        base = 10;
    }

    for (;;) {
        char c = *nptr;
        int v = -1;
        unsigned long new_ret;

        if (c >= 'A' && c <= 'Z') {
            v = c - 'A' + 10;
        } else if (c >= 'a' && c <= 'z') {
            v = c - 'a' + 10;
        } else if (c >= '0' && c <= '9') {
            v = c - '0';
        }

        if (v < 0 || v >= base) {
            if (endptr) {
                *endptr = (char *) nptr;
            }
            break;
        }

        new_ret = ret * base;
        if (new_ret / base != ret ||
                new_ret + v < new_ret ||
                ret == ULONG_MAX) {
            ret = ULONG_MAX;
            errno = ERANGE;
        } else {
            ret = new_ret + v;
        }

        nptr++;
    }

    if (neg && ret != ULONG_MAX) {
        ret = -ret;
    }

    return ret;
}