jetbrains.exodus.util.StringInterner.kt Maven / Gradle / Ivy
/**
* Copyright 2010 - 2022 JetBrains s.r.o.
*
* 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
*
* https://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 jetbrains.exodus.util
import jetbrains.exodus.core.dataStructures.ConcurrentObjectCache
import jetbrains.exodus.system.JVMConstants
import kotlin.math.min
class StringInterner private constructor(size: Int = INTERNER_SIZE) {
private val cache: ConcurrentObjectCache
init {
cache = ConcurrentObjectCache(size, NUMBER_OF_GENERATIONS)
}
fun doIntern(s: String?): String? {
if (s == null || s.length > MAX_SIZE_OF_CACHED_STRING) return s
val cached = cache.tryKey(s)
if (cached != null) {
return cached
}
val copy = if (JVMConstants.IS_JAVA8_OR_HIGHER) s else s + "" // to avoid large cached substrings
cache.cacheObject(copy, copy)
return copy
}
fun doIntern(builder: StringBuilder, maxLen: Int): String {
val result = builder.toString()
if (builder.length <= maxLen) {
val cached = cache.tryKey(result)
if (cached != null) {
return cached
}
cache.cacheObject(result, result)
}
return result
}
companion object {
private val NUMBER_OF_GENERATIONS = Integer.getInteger("exodus.util.stringInternerNumberOfGenerations", 5)
private val MAX_SIZE_OF_CACHED_STRING = Integer.getInteger("exodus.util.stringInternerMaxEntrySize", 1000)
private val INTERNER_SIZE = Integer.getInteger("exodus.util.stringInternerCacheSize", 15991 * NUMBER_OF_GENERATIONS)
private val DEFAULT_INTERNER = StringInterner()
@JvmStatic
fun intern(s: String?) = DEFAULT_INTERNER.doIntern(s)
@JvmStatic
fun intern(builder: StringBuilder, maxLen: Int) = DEFAULT_INTERNER.doIntern(builder, min(maxLen, MAX_SIZE_OF_CACHED_STRING))
@JvmStatic
fun newInterner(size: Int) = StringInterner(size)
}
}