com.google.devtools.build.lib.bazel.repository.HttpDownloader.java Source code

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Here is the source code for com.google.devtools.build.lib.bazel.repository.HttpDownloader.java

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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.bazel.repository;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.hash.Hasher;
import com.google.common.hash.Hashing;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;

/**
 * Helper class for downloading a file from a URL.
 */
public class HttpDownloader {
    private static final int BUFFER_SIZE = 2048;

    private final URL url;
    private final String sha256;
    private final Path outputDirectory;

    HttpDownloader(URL url, String sha256, Path outputDirectory) {
        this.url = url;
        this.sha256 = sha256;
        this.outputDirectory = outputDirectory;
    }

    /**
     * Attempt to download a file from the repository's URL. Returns the path to the file downloaded.
     */
    public Path download() throws IOException {
        String filename = new PathFragment(url.getPath()).getBaseName();
        if (filename.isEmpty()) {
            filename = "temp";
        }
        Path destination = outputDirectory.getRelative(filename);

        try (OutputStream outputStream = destination.getOutputStream()) {
            ReadableByteChannel rbc = getChannel(url);
            ByteBuffer byteBuffer = ByteBuffer.allocate(BUFFER_SIZE);
            while (rbc.read(byteBuffer) > 0) {
                byteBuffer.flip();
                while (byteBuffer.hasRemaining()) {
                    outputStream.write(byteBuffer.get());
                }
                byteBuffer.flip();
            }
        } catch (IOException e) {
            throw new IOException("Error downloading " + url + " to " + destination + ": " + e.getMessage());
        }

        String downloadedSha256;
        try {
            downloadedSha256 = getHash(Hashing.sha256().newHasher(), destination);
        } catch (IOException e) {
            throw new IOException("Could not hash file " + destination + ": " + e.getMessage()
                    + ", expected SHA-256 of " + sha256 + ")");
        }
        if (!downloadedSha256.equals(sha256)) {
            throw new IOException("Downloaded file at " + destination + " has SHA-256 of " + downloadedSha256
                    + ", does not match expected SHA-256 (" + sha256 + ")");
        }
        return destination;
    }

    @VisibleForTesting
    protected ReadableByteChannel getChannel(URL url) throws IOException {
        return Channels.newChannel(url.openStream());
    }

    public static String getHash(Hasher hasher, Path path) throws IOException {
        byte byteBuffer[] = new byte[BUFFER_SIZE];
        try (InputStream stream = path.getInputStream()) {
            int numBytesRead = stream.read(byteBuffer);
            while (numBytesRead != -1) {
                if (numBytesRead != 0) {
                    // If more than 0 bytes were read, add them to the hash.
                    hasher.putBytes(byteBuffer, 0, numBytesRead);
                }
                numBytesRead = stream.read(byteBuffer);
            }
        }
        return hasher.hash().toString();
    }
}