com.facebook.buck.rules.Sha1HashCode.java Source code

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Here is the source code for com.facebook.buck.rules.Sha1HashCode.java

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/*
 * Copyright 2013-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.rules;

import com.google.common.base.Charsets;
import com.google.common.base.Function;
import com.google.common.base.Objects;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.hash.HashCode;
import com.google.common.hash.Hashing;

import java.util.UUID;
import java.util.regex.Pattern;

/**
 * A typesafe representation of a SHA-1 hash. It is safer to pass this around than a {@link String}.
 */
public final class Sha1HashCode {

    /**
     * Takes a string and uses it to construct a {@link Sha1HashCode}.
     * <p>
     * Is likely particularly useful with {@link Optional#transform(Function)}.
     */
    public static final Function<String, Sha1HashCode> TO_SHA1 = new Function<String, Sha1HashCode>() {
        @Override
        public Sha1HashCode apply(String hash) {
            return new Sha1HashCode(hash);
        }
    };

    private static final Pattern SHA1_PATTERN = Pattern.compile("[a-f0-9]{40}");

    private final String hash;

    /**
     * @param hash Must be a 40-character string from the alphabet [a-f0-9].
     */
    public Sha1HashCode(String hash) {
        Preconditions.checkNotNull(hash);
        Preconditions.checkArgument(SHA1_PATTERN.matcher(hash).matches(), "Should be 40 lowercase hex chars: %s.",
                hash);
        this.hash = hash;
    }

    public static Sha1HashCode fromHashCode(HashCode hashCode) {
        Preconditions.checkNotNull(hashCode);
        return new Sha1HashCode(Hashing.sha1().newHasher().putBytes(hashCode.asBytes()).hash().toString());
    }

    /**
     * @return the hash as a 40-character string from the alphabet [a-f0-9].
     */
    public String getHash() {
        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof Sha1HashCode)) {
            return false;
        }

        Sha1HashCode that = (Sha1HashCode) obj;
        return Objects.equal(this.hash, that.hash);
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(hash);
    }

    /** Same as {@link #getHash()}. */
    @Override
    public String toString() {
        return getHash();
    }

    public static Sha1HashCode newRandomHashCode() {
        HashCode randomHashCode = Hashing.sha1().newHasher().putString(UUID.randomUUID().toString(), Charsets.UTF_8)
                .hash();
        return new Sha1HashCode(randomHashCode.toString());
    }
}