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// Copyright 2018 The Bazel Authors. All rights reserved.
//
// 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.build.lib.vfs;
import com.google.common.collect.ImmutableList;
import com.google.common.hash.HashFunction;
import com.google.common.hash.Hashing;
import com.google.devtools.common.options.Converter;
import com.google.devtools.common.options.OptionsParsingException;
import java.util.HashMap;
import java.util.List;
import java.util.Map.Entry;
/** Type of hash function to use for digesting files. */
// The underlying HashFunctions are immutable and thread safe.
public class DigestHashFunction {
private static final HashMap<String, DigestHashFunction> hashFunctionRegistry = new HashMap<>();
public static final DigestHashFunction MD5 = DigestHashFunction.register(Hashing.md5(), "MD5");
public static final DigestHashFunction SHA1 =
DigestHashFunction.register(Hashing.sha1(), "SHA-1", "SHA1");
public static final DigestHashFunction SHA256 =
DigestHashFunction.register(Hashing.sha256(), "SHA-256", "SHA256");
private final HashFunction hash;
private final String name;
private DigestHashFunction(HashFunction hash, String name) {
this.hash = hash;
this.name = name;
}
public HashFunction getHash() {
return hash;
}
public boolean isValidDigest(byte[] digest) {
// TODO(b/109764197): Remove this check to accept variable-length hashes.
return digest != null && digest.length * 8 == hash.bits();
}
@Override
public String toString() {
return name;
}
/**
* Creates a new DigestHashFunction that is registered to be recognized by its name in {@link
* DigestFunctionConverter}.
*
* @param hashName the canonical name for this hash function.
* @param altNames alternative names that will be mapped to this function by the converter but
* will not serve as the canonical name for the DigestHashFunction.
* @param hash The {@link HashFunction} to register.
* @throws IllegalArgumentException if the name is already registered.
*/
public static DigestHashFunction register(
HashFunction hash, String hashName, String... altNames) {
DigestHashFunction hashFunction = new DigestHashFunction(hash, hashName);
List<String> names = ImmutableList.<String>builder().add(hashName).add(altNames).build();
synchronized (hashFunctionRegistry) {
for (String name : names) {
if (hashFunctionRegistry.containsKey(name)) {
throw new IllegalArgumentException("Hash function " + name + " is already registered.");
}
hashFunctionRegistry.put(name, hashFunction);
}
}
return hashFunction;
}
/** Converts a string to its registered {@link DigestHashFunction}. */
public static class DigestFunctionConverter implements Converter<DigestHashFunction> {
@Override
public DigestHashFunction convert(String input) throws OptionsParsingException {
for (Entry<String, DigestHashFunction> possibleFunctions : hashFunctionRegistry.entrySet()) {
if (possibleFunctions.getKey().equalsIgnoreCase(input)) {
return possibleFunctions.getValue();
}
}
throw new OptionsParsingException("Not a valid hash function.");
}
@Override
public String getTypeDescription() {
return "hash function";
}
}
}
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