com.facebook.buck.jvm.java.abi.JarReader.java Source code

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Here is the source code for com.facebook.buck.jvm.java.abi.JarReader.java

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/*
 * Copyright 2017-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.jvm.java.abi;

import com.google.common.base.Preconditions;
import com.google.common.collect.Iterables;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.util.List;
import javax.annotation.Nullable;
import org.objectweb.asm.ClassVisitor;

/** A {@link LibraryReader} that reads from a jar file. */
class JarReader implements LibraryReader {
    private final Path jarPath;
    @Nullable
    FileSystem fileSystem;
    @Nullable
    private DirectoryReader inner;
    private boolean closed = false;

    JarReader(Path jarPath) {
        this.jarPath = jarPath;
    }

    @Override
    public List<Path> getRelativePaths() throws IOException {
        return getInner().getRelativePaths();
    }

    @Override
    public InputStream openResourceFile(Path relativePath) throws IOException {
        return getInner().openResourceFile(relativePath);
    }

    @Override
    public void visitClass(Path relativePath, ClassVisitor cv) throws IOException {
        getInner().visitClass(relativePath, cv);
    }

    @Override
    public void close() throws IOException {
        if (fileSystem != null) {
            fileSystem.close();
            fileSystem = null;
            inner = null;
            closed = true;
        }
    }

    private DirectoryReader getInner() throws IOException {
        // Actually had a file descriptor leak because something was reopening this after it was closed,
        // so let's make sure we crash and detect it if it happens again.
        Preconditions.checkState(!closed);
        if (inner == null) {
            fileSystem = FileSystems.newFileSystem(jarPath, null);
            inner = new DirectoryReader(Iterables.getOnlyElement(fileSystem.getRootDirectories()));
        }

        return inner;
    }
}