ladybird/Libraries/LibJS/Runtime/NumberPrototype.cpp

/*
 * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.
 */

#include <LibJS/Interpreter.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/NumberObject.h>
#include <LibJS/Runtime/NumberPrototype.h>

namespace JS {

static const u8 max_precision_for_radix[37] = {
    0,  0,  52, 32, 26, 22, 20, 18, 17, 16,
    15, 15, 14, 14, 13, 13, 13, 12, 12, 12,
    12, 11, 11, 11, 11, 11, 11, 10, 10, 10,
    10, 10, 10, 10, 10, 10, 10,
};

static char digits[] = "0123456789abcdefghijklmnopqrstuvwxyz";

NumberPrototype::NumberPrototype(GlobalObject& global_object)
    : NumberObject(0, *global_object.object_prototype())
{
}

void NumberPrototype::initialize(GlobalObject& object)
{
    Object::initialize(object);

    define_native_function("toString", to_string, 1, Attribute::Configurable | Attribute::Writable);
}

NumberPrototype::~NumberPrototype()
{
}

JS_DEFINE_NATIVE_FUNCTION(NumberPrototype::to_string)
{
    Value number_value;

    auto this_value = interpreter.this_value(global_object);
    if (this_value.is_number()) {
        number_value = this_value;
    } else if (this_value.is_object() && this_value.as_object().is_number_object()) {
        number_value = static_cast<NumberObject&>(this_value.as_object()).value_of();
    } else {
        interpreter.throw_exception<TypeError>(ErrorType::NumberIncompatibleThis, "toString");
        return {};
    }

    int radix;
    auto argument = interpreter.argument(0);
    if (argument.is_undefined()) {
        radix = 10;
    } else {
        radix = argument.to_i32(interpreter);
    }

    if (interpreter.exception() || radix < 2 || radix > 36) {
        interpreter.throw_exception<RangeError>(ErrorType::InvalidRadix);
        return {};
    }

    if (number_value.is_positive_infinity())
        return js_string(interpreter, "Infinity");
    if (number_value.is_negative_infinity())
        return js_string(interpreter, "-Infinity");
    if (number_value.is_nan())
        return js_string(interpreter, "NaN");
    if (number_value.is_positive_zero() || number_value.is_negative_zero())
        return js_string(interpreter, "0");

    double number = number_value.as_double();
    bool negative = number < 0;
    if (negative)
        number *= -1;

    int int_part = floor(number);
    double decimal_part = number - int_part;

    Vector<char> backwards_characters;

    if (int_part == 0) {
        backwards_characters.append('0');
    } else {
        while (int_part > 0) {
            backwards_characters.append(digits[int_part % radix]);
            int_part /= radix;
        }
    }

    Vector<char> characters;
    if (negative)
        characters.append('-');

    // Reverse characters;
    for (ssize_t i = backwards_characters.size() - 1; i >= 0; --i) {
        characters.append(backwards_characters[i]);
    }

    // decimal part
    if (decimal_part != 0.0) {
        characters.append('.');

        int precision = max_precision_for_radix[radix];

        for (int i = 0; i < precision; ++i) {
            decimal_part *= radix;
            int integral = floor(decimal_part);
            characters.append(digits[integral]);
            decimal_part -= integral;
        }

        while (characters.last() == '0')
            characters.take_last();
    }

    return js_string(interpreter, String(characters.data(), characters.size()));
}

}