Function strtoul

src/fl/stl/cstdlib.cpp.hpp:158–228

}

unsigned long strtoul(const char* str, char** endptr, int base) {
    if (!str) {
        if (endptr) {
            *endptr = const_cast<char*>(str);
        }
        return 0;
    }

    const char* p = str;
    unsigned long result = 0;

    // Skip leading whitespace
    while (*p == ' ' || *p == '\t' || *p == '\n' || *p == '\r' || *p == '\f' || *p == '\v') {
        p++;
    }

    // Handle optional + sign (ignore - for unsigned)
    if (*p == '+') {
        p++;
    } else if (*p == '-') {
        // Negative values wrap around for unsigned
        p++;
    }

    // Auto-detect base if base is 0
    if (base == 0) {
        if (*p == '0') {
            if (*(p + 1) == 'x' || *(p + 1) == 'X') {
                base = 16;
                p += 2;
            } else {
                base = 8;
                p++;
            }
        } else {
            base = 10;
        }
    } else if (base == 16) {
        // Skip optional 0x/0X prefix for base 16
        if (*p == '0' && (*(p + 1) == 'x' || *(p + 1) == 'X')) {
            p += 2;
        }
    }

    // Validate base
    if (base < 2 || base > 36) {
        if (endptr) {
            *endptr = const_cast<char*>(str);
        }
        return 0;
    }

    // Parse digits
    const char* start = p;
    while (*p && isDigitInBase(*p, base)) {
        result = result * base + charToDigit(*p);
        p++;
    }