gradle-master/subprojects/files/src/main/java/org/gradle/api/internal/file/archive/impl/FileZipInput.java
/*
 * Copyright 2020 the original author or authors.
 *
 * 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 org.gradle.api.internal.file.archive.impl;

import com.google.common.collect.AbstractIterator;
import org.gradle.api.internal.file.archive.ZipEntry;
import org.gradle.api.internal.file.archive.ZipInput;
import org.gradle.internal.file.FileException;
import org.gradle.internal.io.IoFunction;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.zip.ZipFile;

public class FileZipInput implements ZipInput {

    /**
     * Creates a stream of the entries in the given zip file. Caller is responsible for closing the return value.
     *
     * @throws FileException on failure to open the Zip
     */
    public static ZipInput create(File file) throws FileException {
        if (isZipFileSafeToUse()) {
            return new FileZipInput(file);
        } else {
            try {
                return new StreamZipInput(new FileInputStream(file));
            } catch (FileNotFoundException e) {
                throw new FileException(e);
            }
        }
    }

    /**
     * {@link ZipFile} is more efficient, but causes memory leaks on older Java versions, so we only use it on more recent ones.
     */
    private static boolean isZipFileSafeToUse() {
        String versionString = System.getProperty("java.specification.version");
        // Java versions 8 and older had 1.8 versioning scheme, later ones have single number 9, 10, ...
        String[] versionParts = versionString.split("\\.");
        if (versionParts.length < 1) {
            throw new IllegalArgumentException("Could not determine java version from '" + versionString + "'.");
        }
        return Integer.parseInt(versionParts[0]) >= 11;
    }

    private final ZipFile file;
    private final Enumeration<? extends java.util.zip.ZipEntry> entries;

    private FileZipInput(File file) {
        try {
            this.file = new ZipFile(file);
        } catch (IOException e) {
            throw new FileException(e);
        }
        this.entries = this.file.entries();
    }

    @Override
    public Iterator<ZipEntry> iterator() {
        return new AbstractIterator<ZipEntry>() {
            @Override
            protected ZipEntry computeNext() {
                if (!entries.hasMoreElements()) {
                    return endOfData();
                }
                return new FileZipEntry(entries.nextElement());
            }
        };
    }

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

    private class FileZipEntry extends AbstractZipEntry {
        public FileZipEntry(java.util.zip.ZipEntry entry) {
            super(entry);
        }

        @Override
        public <T> T withInputStream(IoFunction<InputStream, T> action) throws IOException {
            InputStream inputStream = getInputStream();
            try {
                return action.apply(inputStream);
            } finally {
                inputStream.close();
            }
        }

        private InputStream getInputStream() {
            try {
                return file.getInputStream(getEntry());
            } catch (IOException e) {
                throw new FileException(e);
            }
        }

        @Override
        public boolean canReopen() {
            return true;
        }
    }
}
