com.google.template.soy.base.internal.SoyJarFileWriter.java Source code

Introduction

Here is the source code for com.google.template.soy.base.internal.SoyJarFileWriter.java

Source

/*
 * Copyright 2017 Google 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.google.template.soy.base.internal;

import com.google.common.io.ByteSource;
import java.io.IOException;
import java.io.OutputStream;
import java.util.jar.Attributes;
import java.util.jar.JarOutputStream;
import java.util.jar.Manifest;
import java.util.zip.ZipEntry;

/**
 * A SoyJarWriter can populate a jar file with a number of entries ensuring that there is a proper
 * manifest and that all timestamps are stripped from the outputs which helps ensure determinism.
 */
public final class SoyJarFileWriter implements AutoCloseable {

    private final DeterministicJarOutputStream stream;

    public SoyJarFileWriter(OutputStream stream) throws IOException {
        this.stream = new DeterministicJarOutputStream(stream);
    }

    /** Writes a single entry to the jar. */
    public void writeEntry(String path, ByteSource contents) throws IOException {
        stream.putNextEntry(new ZipEntry(path));
        contents.copyTo(stream);
        stream.closeEntry();
    }

    @Override
    public void close() throws IOException {
        stream.close();
    }

    private static final class DeterministicJarOutputStream extends JarOutputStream {
        DeterministicJarOutputStream(OutputStream outputStream) throws IOException {
            super(outputStream, standardSoyJarManifest());
        }

        @Override
        public void putNextEntry(ZipEntry ze) throws IOException {
            ze.setTime(0); // set an explicit timestamp to zero so we generate deterministic outputs
            super.putNextEntry(ze);
        }
    }

    /** Returns a simple jar manifest. */
    private static Manifest standardSoyJarManifest() {
        Manifest mf = new Manifest();
        mf.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
        mf.getMainAttributes().put(new Attributes.Name("Created-By"), "soy");
        return mf;
    }
}