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/*
* Copyright 2022 Google LLC
* Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
*
* 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 com.google.devtools.ksp
// TODO: garbage collect underlying sequence after exhaust.
class MemoizedSequence<T>(sequence: Sequence<T>) : Sequence<T> {
private val cache = arrayListOf<T>()
private val iter: Iterator<T> by lazy {
sequence.iterator()
}
private inner class CachedIterator() : Iterator<T> {
var idx = 0
override fun hasNext(): Boolean {
return idx < cache.size || iter.hasNext()
}
override fun next(): T {
if (idx == cache.size) {
cache.add(iter.next())
}
val value = cache[idx]
idx += 1
return value
}
}
override fun iterator(): Iterator<T> {
return CachedIterator()
}
}
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