os-k/kaleid/libc/strtol.c

//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:       strto*l() family                                              //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2020 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <libc.h>
#include <lib/buf.h>

long strtol(const char *str, char **endp, int base) {
    ulong n;
    bool neg = 0;
    const char *save, *start = str;
    
    assert(str != NULL);

    char c = *str;

    // Ignore leading spaces
    while (isspace(c)) {
        c = *str++;
    }

    // Accept any +/-'s, whatever the base
    // In particular we accept things like "-0xF"
    if (c == '+')
        c = *str++;
    else if (c == '-') {
        c = *str++;
        neg = 1;
    }

    // Accept 0/0b/0B/0x/0X and guess base if needed
    if (c == '0') {
        c = *str++;
        if ((base == 0 || base == 16) && (c == 'x' || c == 'X')) {
            c = *str++;
            base = 16;
        }
        else if ((base == 0 || base == 2) && (c == 'b' || c == 'B')) {
            c = *str++;
            base = 2;
        }

        else if (base == 0)
            base = 8;
    }

    // base==0 but no leading '0' - assume it's decimal
    if (base == 0)
        base = 10;

    //
    // Extract the number from the string
    // We do not check whether the number actually fits
    // That's why our accumulator 'n' needs to be unsigned, otherwise
    // containing a number too large would cause a signed overflow and UB
    //
    save = str;
    for (n = 0;; c = *str) {
        if (isdigit(c))
            c -= '0';
        else if (isalpha(c))
            c -= isupper(c) ? 'A' - 10 : 'a' - 10;
        else
            break;

        if (c >= base)
            break;
        else {
            str++;
            n = (n * base) + c;
        }
    }

    // Save where we stopped in *endp (optional)
    // If 'str' is still '== save', no digit were consummed
    if (endp != NULL)
        *endp = (char *)(str == save ? start : str);

    return neg ? -(long)n : (long)n;
}


//
// Made from the code above by removing "neg"
//
ulong strtoul(const char *str, char **endp, int base) {
    ulong n;
    const char *save, *start = str;
    
    assert(str != NULL);

    char c = *str;

    while (isspace(c)) {
        c = *str++;
    }

    if (c == '+')
        c = *str++;

    if (c == '0') {
        c = *str++;
        if ((base == 0 || base == 16) && (c == 'x' || c == 'X')) {
            c = *str++;
            base = 16;
        }
        else if ((base == 0 || base == 2) && (c == 'b' || c == 'B')) {
            c = *str++;
            base = 2;
        }

        else if (base == 0)
            base = 8;
    }

    if (base == 0)
        base = 10;

    save = str;
    for (n = 0;; c = *str) {
        if (isdigit(c))
            c -= '0';
        else if (isalpha(c))
            c -= isupper(c) ? 'A' - 10 : 'a' - 10;
        else
            break;

        if (c >= base)
            break;
        else {
            str++;
            n = (n * base) + c;
        }
    }
    if (endp != NULL)
        *endp = (char *)(str == save ? start : str);

    return (long)n;
}