jj.resource.Sha1Resource.java Source code

Introduction

Here is the source code for jj.resource.Sha1Resource.java

Source

/*
 *    Copyright 2012 Jason Miller
 *
 * 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 jj.resource;

import static java.nio.charset.StandardCharsets.US_ASCII;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.inject.Inject;

import jj.resource.Sha1ResourceCreator.Sha1ResourceTarget;
import jj.util.SHA1Helper;

/**
 * internal helper to manage a saved SHA-1 hash for large files, so we only read it once
 * 
 * @author jason
 *
 */
class Sha1Resource extends AbstractResource {

    // empirical magic numbers - the sha1 hash is 40 hex digits, and the max long value as a decimal is 19 digits
    private static final Pattern FORMAT = Pattern.compile("^([a-f\\d]{40})(\\d{1,19})$");

    private final String representedSha;
    private final long representedFileSize;

    private final String sha1;

    @Inject
    Sha1Resource(final Dependencies dependencies, final Path path, final Sha1ResourceTarget target)
            throws IOException {
        super(dependencies);

        // 3 possibilities
        // either there is no file at path, so we read in our target bytes to make one
        // or there is a file, but it's out of date, so we read in our target bytes and make a new one
        // or it's all good and we use it

        // 59 is the maximum size of the contents as described above.
        ByteBuf byteBuffer = Unpooled.buffer(59, 59);
        String sha = null;
        long size = -1;

        if (Files.exists(path)) {
            byteBuffer.writeBytes(Files.readAllBytes(path));
            Matcher matcher = FORMAT.matcher(byteBuffer.toString(US_ASCII));
            if (!matcher.matches()) {
                throw new AssertionError("someone messed with the contents of Sha1Resource file");
            }
            sha = matcher.group(1);
            size = Long.parseLong(matcher.group(2));
        } else {
            sha = SHA1Helper.keyFor(target.resource.path());
            size = target.resource.size();

            Files.write(path, (sha + size).getBytes(US_ASCII));
        }

        // yuckerdo! but java makes this hard to extract
        // TODO - make this nicer. you have a test to validate it and everything
        if (size != target.resource.size()) {
            sha = SHA1Helper.keyFor(target.resource.path());
            size = target.resource.size();

            Files.write(path, (sha + size).getBytes(US_ASCII));
        }

        representedSha = sha;
        representedFileSize = size;

        sha1 = SHA1Helper.keyFor(representedSha, String.valueOf(size));

        target.resource.addDependent(this);
    }

    @Override
    protected String extension() {
        return Sha1ResourceCreator.EXTENSION;
    }

    public String representedSha() {
        return representedSha;
    }

    public long representedFileSize() {
        return representedFileSize;
    }

    @Override
    public String sha1() {
        return sha1;
    }

    @Override
    public boolean needsReplacing() throws IOException {
        // we only get replaced as a result of our master file going out of scope
        // i think, anyway
        return false;
    }
}