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// Copyright 2014 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.util;
import com.google.common.io.ByteStreams;
import com.google.devtools.build.lib.vfs.DigestHashFunction;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.protobuf.CodedOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.DigestException;
import java.security.DigestOutputStream;
import java.security.MessageDigest;
import java.util.Map;
import java.util.UUID;
import java.util.function.Consumer;
import javax.annotation.Nullable;
/**
* Simplified wrapper for computing message digests.
*
* @see java.security.MessageDigest
*/
public final class Fingerprint implements Consumer<String> {
// Make novel use of a CodedOutputStream, which is good at efficiently serializing data. By
// flushing at the end of each digest we can continue to use the stream.
private final CodedOutputStream codedOut;
private final MessageDigest messageDigest;
/** Creates and initializes a new instance. */
public Fingerprint(DigestHashFunction digestFunction) {
messageDigest = digestFunction.cloneOrCreateMessageDigest();
// This is a lot of indirection, but CodedOutputStream does a reasonable job of converting
// strings to bytes without creating a whole bunch of garbage, which pays off.
codedOut =
CodedOutputStream.newInstance(
new DigestOutputStream(ByteStreams.nullOutputStream(), messageDigest),
/*bufferSize=*/ 1024);
}
public Fingerprint() {
// TODO(b/112460990): Use the value from DigestHashFunction.getDefault(), but check for
// contention.
this(DigestHashFunction.MD5);
}
/**
* Completes the hash computation by doing final operations and resets the underlying state,
* allowing this instance to be used again.
*
* @return the digest as a 16-byte array
* @see java.security.MessageDigest#digest()
*/
public byte[] digestAndReset() {
try {
codedOut.flush();
} catch (IOException e) {
throw new IllegalStateException("failed to flush", e);
}
return messageDigest.digest();
}
/**
* Completes the hash computation by doing final operations and resets the underlying state,
* allowing this instance to be used again.
*
* <p>Instead of returning a digest, this method writes the digest straight into the supplied byte
* array, at the given offset.
*
* @see java.security.MessageDigest#digest()
*/
public void digestAndReset(byte[] buf, int offset, int len) {
try {
codedOut.flush();
messageDigest.digest(buf, offset, len);
} catch (IOException e) {
throw new IllegalStateException("failed to flush", e);
} catch (DigestException e) {
throw new IllegalStateException("failed to digest", e);
}
}
/** Same as {@link #digestAndReset()}, except returns the digest in hex string form. */
public String hexDigestAndReset() {
return hexDigest(digestAndReset());
}
/** Updates the digest with 0 or more bytes. */
public Fingerprint addBytes(byte[] input) {
addBytes(input, 0, input.length);
return this;
}
/** Updates the digest with the specified number of bytes starting at offset. */
public Fingerprint addBytes(byte[] input, int offset, int len) {
try {
codedOut.write(input, offset, len);
} catch (IOException e) {
throw new IllegalStateException("failed to write bytes", e);
}
return this;
}
/** Updates the digest with a boolean value. */
public Fingerprint addBoolean(boolean input) {
try {
codedOut.writeBoolNoTag(input);
} catch (IOException e) {
throw new IllegalStateException(e);
}
return this;
}
/** Same as {@link #addBoolean(boolean)}, except considers nullability. */
public Fingerprint addNullableBoolean(Boolean input) {
if (input == null) {
addBoolean(false);
} else {
addBoolean(true);
addBoolean(input);
}
return this;
}
/** Updates the digest with the varint representation of input. */
public Fingerprint addInt(int input) {
try {
codedOut.writeInt32NoTag(input);
} catch (IOException e) {
throw new IllegalStateException(e);
}
return this;
}
/** Updates the digest with the signed varint representation of input. */
Fingerprint addSInt(int input) {
try {
codedOut.writeSInt32NoTag(input);
} catch (IOException e) {
throw new IllegalStateException(e);
}
return this;
}
/** Updates the digest with the varint representation of a long value. */
public Fingerprint addLong(long input) {
try {
codedOut.writeInt64NoTag(input);
} catch (IOException e) {
throw new IllegalStateException("failed to write long", e);
}
return this;
}
/** Same as {@link #addInt(int)}, except considers nullability. */
public Fingerprint addNullableInt(@Nullable Integer input) {
if (input == null) {
addBoolean(false);
} else {
addBoolean(true);
addInt(input);
}
return this;
}
/** Updates the digest with a UUID. */
public Fingerprint addUUID(UUID uuid) {
addLong(uuid.getLeastSignificantBits());
addLong(uuid.getMostSignificantBits());
return this;
}
/** Updates the digest with a String using UTF8 encoding. */
public Fingerprint addString(String input) {
try {
codedOut.writeStringNoTag(input);
} catch (IOException e) {
throw new IllegalStateException("failed to write string", e);
}
return this;
}
/** Same as {@link #addString(String)}, except considers nullability. */
public Fingerprint addNullableString(@Nullable String input) {
if (input == null) {
addBoolean(false);
} else {
addBoolean(true);
addString(input);
}
return this;
}
/** Updates the digest with a {@link Path}. */
public Fingerprint addPath(Path input) {
addString(input.getPathString());
return this;
}
/** Updates the digest with a {@link PathFragment}. */
public Fingerprint addPath(PathFragment input) {
return addString(input.getPathString());
}
/**
* Add the supplied sequence of {@link String}s to the digest as an atomic unit, that is this is
* different from adding them each individually.
*/
public Fingerprint addStrings(Iterable<String> inputs) {
int count = 0;
for (String input : inputs) {
addString(input);
count++;
}
addInt(count);
return this;
}
/** Updates the digest with the supplied map. */
public Fingerprint addStringMap(Map<String, String> inputs) {
addInt(inputs.size());
for (Map.Entry<String, String> entry : inputs.entrySet()) {
addString(entry.getKey());
addString(entry.getValue());
}
return this;
}
/**
* Add the supplied sequence of {@link PathFragment}s to the digest as an atomic unit, that is
* this is different from adding each item individually.
*
* @param inputs the paths with which to update the digest
*/
public Fingerprint addPaths(Iterable<PathFragment> inputs) {
int count = 0;
for (PathFragment path : inputs) {
addPath(path);
count++;
}
addInt(count);
return this;
}
private static String hexDigest(byte[] digest) {
StringBuilder b = new StringBuilder(32);
for (int i = 0; i < digest.length; i++) {
int n = digest[i];
b.append("0123456789abcdef".charAt((n >> 4) & 0xF));
b.append("0123456789abcdef".charAt(n & 0xF));
}
return b.toString();
}
// -------- Convenience methods ----------------------------
/**
* Computes the hex digest from a String using UTF8 encoding and returning the hexDigest().
*
* @param input the String from which to compute the digest
*/
public static String getHexDigest(String input) {
// TODO(b/112460990): This convenience method, if kept should not use MD5 by default, but should
// use the value from DigestHashFunction.getDefault(). However, this gets called during class
// loading in a few places, before setDefault() has been called, so these call-sites should be
// removed before this can be done safely.
return hexDigest(
DigestHashFunction.MD5
.cloneOrCreateMessageDigest()
.digest(input.getBytes(StandardCharsets.UTF_8)));
}
@Override
public void accept(String s) {
addString(s);
}
}