001/*
002 * Licensed under the Apache License, Version 2.0 (the "License");
003 * you may not use this file except in compliance with the License.
004 * You may obtain a copy of the License at
005 *
006 * http://www.apache.org/licenses/LICENSE-2.0
007 *
008 * Unless required by applicable law or agreed to in writing, software
009 * distributed under the License is distributed on an "AS IS" BASIS,
010 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
011 * See the License for the specific language governing permissions and
012 * limitations under the License.
013 */
014package de.softwareforge.testing.postgres.embedded;
015
016import static com.google.common.base.Preconditions.checkState;
017
018import java.io.IOException;
019import java.io.InputStream;
020
021import com.google.common.hash.Hashing;
022import com.google.common.hash.HashingInputStream;
023import com.google.common.io.BaseEncoding;
024import com.google.common.io.ByteStreams;
025import edu.umd.cs.findbugs.annotations.CheckForNull;
026import edu.umd.cs.findbugs.annotations.NonNull;
027import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
028
029/**
030 * Locates a native binary on the Filesystem. If necessary, it should download the binary first from the network.
031 * <p>
032 * Implementations of this class <b>must</b> implement {@link Object#hashCode()} and {@link Object#equals(Object)} and <i>should</i> implement {@link
033 * Object#toString()}.
034 *
035 * @since 3.0
036 */
037public interface NativeBinaryLocator {
038
039    String INSTALL_DIRECTORY_PREFIX = "bin-";
040
041    /**
042     * Returns an input stream from which the contents of the binary archive can be read.
043     *
044     * @return An input stream. May return null.
045     * @throws IOException If the archive could not be located or read.
046     */
047    @CheckForNull
048    InputStream getInputStream() throws IOException;
049
050    /**
051     * Returns a string identifier that represents the archive returned. This identifier should be stable (same value for the same archive), even across
052     * multiple JVM invocations. The value must only contain characters that can be used as a legal file name.
053     * <p>
054     * The default implementation needs to read the full archive contents and is relatively slow. Implementations of this interface can override this method to
055     * provide a faster way to create a stable identifier based on the specific implementation.
056     * <p>
057     * The default implementation hashes the archive contents and uses it to return a stable file name.
058     *
059     * @return A stable indentifier that can be used as a file name.
060     * @throws IOException If the stream could not be read.
061     */
062    @NonNull
063    @SuppressFBWarnings("NP_NULL_ON_SOME_PATH_FROM_RETURN_VALUE") // false positive
064    default String getIdentifier() throws IOException {
065        try (InputStream installationArchive = getInputStream()) {
066            checkState(installationArchive != null, "Locator '%s' did not find a suitable archive to unpack!", toString());
067            try (HashingInputStream hashStream = new HashingInputStream(Hashing.murmur3_128(), installationArchive)) {
068                ByteStreams.exhaust(hashStream);
069                return INSTALL_DIRECTORY_PREFIX + BaseEncoding.base16().encode(hashStream.hash().asBytes());
070            }
071        }
072    }
073}