com.facebook.buck.util.hashing.StringHashing.java Source code

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Here is the source code for com.facebook.buck.util.hashing.StringHashing.java

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/*
 * Copyright 2015-present Facebook, Inc.
 *
 * 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.facebook.buck.util.hashing;

import com.google.common.hash.Hasher;

public class StringHashing {
    // Utility class, do not instantiate.
    private StringHashing() {
    }

    /**
     * Encodes the length of the string in UTF-16 code units, then the UTF-16 code units of the
     * string.
     *
     * <p>Useful to ensure hash codes are different when multiple strings are hashed in order ("foo"
     * then "bar" should hash differently from "foobar").
     */
    public static void hashStringAndLength(Hasher hasher, String string) {
        // We used to hash the UTF-8 bytes of the string, but it takes
        // a lot of unnecessary CPU and memory to do so.
        hasher.putInt(string.length());
        hasher.putUnencodedChars(string);
    }
}