ContainerHelpers.kt
/*
* Copyright 2022 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.collection.internal
import kotlin.jvm.JvmField
@JvmField
internal val EMPTY_INTS = IntArray(0)
@JvmField
internal val EMPTY_LONGS = LongArray(0)
@JvmField
internal val EMPTY_OBJECTS = arrayOfNulls<Any>(0)
internal fun idealIntArraySize(need: Int): Int {
return idealByteArraySize(need * 4) / 4
}
internal fun idealLongArraySize(need: Int): Int {
return idealByteArraySize(need * 8) / 8
}
internal fun idealByteArraySize(need: Int): Int {
for (i in 4..31) {
if (need <= (1 shl i) - 12) {
return (1 shl i) - 12
}
}
return need
}
// null-safe object equals, which is equivalent to `a == b || (a != null && a.equals(b));` in Java.
internal fun equal(a: Any?, b: Any?): Boolean {
return a == b
}
// Same as Arrays.binarySearch(), but doesn't do any argument validation. Very importantly, also
// guarantees consistent result on duplicate values, which is required for indexOfNull in
// SimpleArrayMap, because the mapped hash for `null` is 0, the same as default initialized value.
internal fun binarySearch(array: IntArray, size: Int, value: Int): Int {
var lo = 0
var hi = size - 1
while (lo <= hi) {
val mid = lo + hi ushr 1
val midVal = array[mid]
if (midVal < value) {
lo = mid + 1
} else if (midVal > value) {
hi = mid - 1
} else {
return mid // value found
}
}
return lo.inv() // value not present
}
// Same as Arrays.binarySearch(), but doesn't do any argument validation. Very importantly, also
// guarantees consistent result on duplicate values.
internal fun binarySearch(array: LongArray, size: Int, value: Long): Int {
var lo = 0
var hi = size - 1
while (lo <= hi) {
val mid = lo + hi ushr 1
val midVal = array[mid]
if (midVal < value) {
lo = mid + 1
} else if (midVal > value) {
hi = mid - 1
} else {
return mid // value found
}
}
return lo.inv() // value not present
}