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// Copyright 2014 Google Inc. 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.exec;
import static java.nio.charset.StandardCharsets.US_ASCII;
import com.google.common.io.BaseEncoding;
import com.google.devtools.build.lib.actions.cache.VirtualActionInput;
import com.google.devtools.build.lib.util.Pair;
import com.google.protobuf.ByteString;
import com.google.protobuf.MessageLite;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
* A utility class for obtaining MD5 digests.
* Digests are represented as 32 characters in lowercase ASCII.
*/
public class Digest {
public static final ByteString EMPTY_DIGEST = fromContent(new byte[]{});
private Digest() {
}
/**
* Get the digest from the given byte array.
* @param bytes the byte array.
* @return a digest.
*/
public static ByteString fromContent(byte[] bytes) {
MessageDigest md = newBuilder();
md.update(bytes, 0, bytes.length);
return toByteString(BaseEncoding.base16().lowerCase().encode(md.digest()));
}
/**
* Get the digest from the given ByteBuffer.
* @param buffer the ByteBuffer.
* @return a digest.
*/
public static ByteString fromBuffer(ByteBuffer buffer) {
MessageDigest md = newBuilder();
md.update(buffer);
return toByteString(BaseEncoding.base16().lowerCase().encode(md.digest()));
}
/**
* Gets the digest of the given proto.
*
* @param proto a protocol buffer.
* @return the digest.
*/
public static ByteString fromProto(MessageLite proto) {
MD5OutputStream md5Stream = new MD5OutputStream();
try {
proto.writeTo(md5Stream);
} catch (IOException e) {
throw new IllegalStateException("Unexpected IOException: ", e);
}
return toByteString(md5Stream.getDigest());
}
/**
* Gets the digest and size of a given VirtualActionInput.
*
* @param input the VirtualActionInput.
* @return the digest and size.
*/
public static Pair<ByteString, Long> fromVirtualActionInput(VirtualActionInput input)
throws IOException {
CountingMD5OutputStream md5Stream = new CountingMD5OutputStream();
input.writeTo(md5Stream);
ByteString digest = toByteString(md5Stream.getDigest());
return Pair.of(digest, md5Stream.getSize());
}
/**
* A Sink that does an online MD5 calculation, which avoids forcing us to keep the entire
* proto message in memory.
*/
private static class MD5OutputStream extends OutputStream {
private final MessageDigest md = newBuilder();
@Override
public void write(int b) {
md.update((byte) b);
}
@Override
public void write(byte[] b, int off, int len) {
md.update(b, off, len);
}
public String getDigest() {
return BaseEncoding.base16().lowerCase().encode(md.digest());
}
}
private static final class CountingMD5OutputStream extends MD5OutputStream {
private long size;
@Override
public void write(int b) {
super.write(b);
size++;
}
@Override
public void write(byte[] b, int off, int len) {
super.write(b, off, len);
size += len;
}
public long getSize() {
return size;
}
}
/**
* @param digest the digest to check.
* @return true iff digest is a syntactically legal digest. It must be 32
* characters of hex with lowercase letters.
*/
public static boolean isDigest(ByteString digest) {
if (digest == null || digest.size() != 32) {
return false;
}
for (byte b : digest) {
char c = (char) b;
if ((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')) {
continue;
}
return false;
}
return true;
}
/**
* @param digest the digest.
* @return true iff the digest is that of an empty file.
*/
public static boolean isEmpty(ByteString digest) {
return digest.equals(EMPTY_DIGEST);
}
/**
* @return a new MD5 digest builder.
*/
public static MessageDigest newBuilder() {
try {
return MessageDigest.getInstance("md5");
} catch (NoSuchAlgorithmException e) {
throw new IllegalStateException("MD5 not available", e);
}
}
/**
* Convert a String digest into a ByteString using ascii.
* @param digest the digest in ascii.
* @return the digest as a ByteString.
*/
public static ByteString toByteString(String digest) {
return ByteString.copyFrom(digest.getBytes(US_ASCII));
}
}
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