/*
 * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
 * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
 */

package kotlin.js.internal

private external class ArrayBuffer(size: Int)
private external class Float64Array(buffer: ArrayBuffer)
private external class Float32Array(buffer: ArrayBuffer)
private external class Int32Array(buffer: ArrayBuffer)

@PublishedApi
internal object BitUtils {
    private val buf = ArrayBuffer(8)
    private val bufFloat64 = Float64Array(buf).unsafeCast<DoubleArray>()
    private val bufFloat32 = Float32Array(buf).unsafeCast<FloatArray>()
    private val bufInt32 = Int32Array(buf).unsafeCast<IntArray>()
    private var lowIndex = 0
    private var highIndex = 1

    init {
        bufFloat64[0] = -1.0  // bff00000_00000000
        if (bufInt32[lowIndex] != 0) {
            lowIndex = 1
            highIndex = 0
        }
    }

    fun doubleToRawBits(value: Double): Long {
        bufFloat64[0] = value
        return Long(bufInt32[lowIndex], bufInt32[highIndex])
    }

    fun doubleFromBits(value: Long): Double {
        bufInt32[lowIndex] = value.low
        bufInt32[highIndex] = value.high
        return bufFloat64[0]
    }

    fun floatToRawBits(value: Float): Int {
        bufFloat32[0] = value
        return bufInt32[0]
    }

    fun floatFromBits(value: Int): Float {
        bufInt32[0] = value
        return bufFloat32[0]
    }

    // returns zero value for number with positive sign bit and non-zero value for number with negative sign bit.
    fun doubleSignBit(value: Double): Int {
        bufFloat64[0] = value
        return bufInt32[highIndex] and Int.MIN_VALUE
    }

    fun getNumberHashCode(obj: Double): Int {
        if (jsBitwiseOr(obj, 0).unsafeCast<Double>() === obj) {
            return obj.toInt()
        }

        bufFloat64[0] = obj
        return bufInt32[highIndex] * 31 + bufInt32[lowIndex]
    }
}