com.facebook.buck.io.HashingDeterministicJarWriter.java Source code

Introduction

Here is the source code for com.facebook.buck.io.HashingDeterministicJarWriter.java

Source

/*
 * Copyright 2016-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.io;

import com.facebook.buck.zip.ZipConstants;
import com.google.common.hash.Hashing;
import com.google.common.hash.HashingInputStream;
import com.google.common.io.ByteStreams;

import java.io.InputStream;
import java.io.IOException;
import java.util.jar.JarFile;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

/**
 * Writes a deterministic jar with precomputed hash codes in its MANIFEST.MF.
 */
public class HashingDeterministicJarWriter implements AutoCloseable {
    public static final String DIGEST_ATTRIBUTE_NAME = "Murmur3-128-Digest";

    private final ZipOutputStream jar;
    private final DeterministicJarManifestWriter manifestWriter;

    public HashingDeterministicJarWriter(ZipOutputStream jar) {
        this.jar = jar;
        manifestWriter = new DeterministicJarManifestWriter(jar);
    }

    public HashingDeterministicJarWriter writeEntry(String name, InputStream contents) throws IOException {
        try (HashingInputStream hashingContents = new HashingInputStream(Hashing.murmur3_128(), contents)) {
            writeToJar(name, hashingContents);
            manifestWriter.setEntryAttribute(name, DIGEST_ATTRIBUTE_NAME, hashingContents.hash().toString());
        }
        return this;
    }

    public HashingDeterministicJarWriter writeUnhashedEntry(String name, InputStream contents) throws IOException {
        writeToJar(name, contents);
        contents.close();
        return this;
    }

    @Override
    public void close() throws IOException {
        if (manifestWriter.hasEntries()) {
            putEntry(jar, JarFile.MANIFEST_NAME);
            manifestWriter.write();
            jar.closeEntry();
        }
        jar.close();
    }

    private void writeToJar(String fileName, InputStream stubClassBytes) throws IOException {
        putEntry(jar, fileName);
        ByteStreams.copy(stubClassBytes, jar);
        jar.closeEntry();
    }

    private void putEntry(ZipOutputStream jar, String fileName) throws IOException {
        ZipEntry entry = new ZipEntry(fileName);
        // We want deterministic JARs, so avoid mtimes.
        entry.setTime(ZipConstants.getFakeTime());
        jar.putNextEntry(entry);
    }
}