commonMain.org.antlr.v4.kotlinruntime.atn.PredictionContextCache.kt Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of antlr-kotlin-runtime-jvm Show documentation

Kotlin multiplatform port of ANTLR

There is a newer version: 0.0.18

Show newest version

/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

package org.antlr.v4.kotlinruntime.atn

/** Used to cache [PredictionContext] objects. Its used for the shared
 * context cash associated with contexts in DFA states. This cache
 * can be used for both lexers and parsers.
 */
class PredictionContextCache {
    protected val cache: MutableMap = HashMap()

    /** Add a context to the cache and return it. If the context already exists,
     * return that one instead and do not add a new context to the cache.
     * Protect shared cache from unsafe thread access.
     */
    fun add(ctx: PredictionContext): PredictionContext {
        if (ctx === PredictionContext.EMPTY) return PredictionContext.EMPTY
        val existing = cache[ctx]
        if (existing != null) {
            //			System.out.println(name+" reuses "+existing);
            return existing
        }
        cache.put(ctx, ctx)
        return ctx
    }

    operator fun get(ctx: PredictionContext): PredictionContext? {
        return cache[ctx]
    }

    fun size(): Int {
        return cache.size
    }
}