org.sonar.batch.scan.filesystem.FileHashDigest.java Source code

Introduction

Here is the source code for org.sonar.batch.scan.filesystem.FileHashDigest.java

Source

/*
 * SonarQube, open source software quality management tool.
 * Copyright (C) 2008-2013 SonarSource
 * mailto:contact AT sonarsource DOT com
 *
 * SonarQube is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * SonarQube is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package org.sonar.batch.scan.filesystem;

import org.apache.commons.codec.binary.Hex;
import org.apache.commons.codec.digest.DigestUtils;
import org.apache.commons.io.IOUtils;

import java.io.*;
import java.nio.charset.Charset;
import java.security.MessageDigest;

/**
 * Computes hash of files. Ends of Lines are ignored, so files with
 * same content but different EOL encoding have the same hash.
 */
class FileHashDigest {

    // This singleton aims only to increase the coverage by allowing
    // to test the private method !
    static final FileHashDigest INSTANCE = new FileHashDigest();

    private FileHashDigest() {
    }

    /**
     * Compute hash of a file ignoring line ends differences.
     * Maximum performance is needed.
     */
    String hash(File file, Charset charset) {
        Reader reader = null;
        try {
            MessageDigest md5Digest = DigestUtils.getMd5Digest();
            md5Digest.reset();
            reader = new BufferedReader(new InputStreamReader(new FileInputStream(file), charset));
            int i = reader.read();
            boolean afterCR = true;
            while (i != -1) {
                char c = (char) i;
                if (afterCR) {
                    afterCR = false;
                    if (c == '\n') {
                        // Ignore
                        i = reader.read();
                        continue;
                    }
                }
                if (c == '\r') {
                    afterCR = true;
                    c = '\n';
                }
                md5Digest.update(charToBytesUTF(c));
                i = reader.read();
            }
            return Hex.encodeHexString(md5Digest.digest());
        } catch (IOException e) {
            throw new IllegalStateException(String.format("Fail to compute hash of file %s with charset %s",
                    file.getAbsolutePath(), charset), e);
        } finally {
            IOUtils.closeQuietly(reader);
        }
    }

    private byte[] charToBytesUTF(char c) {
        char[] buffer = new char[] { c };
        byte[] b = new byte[buffer.length << 1];
        for (int i = 0; i < buffer.length; i++) {
            int bpos = i << 1;
            b[bpos] = (byte) ((buffer[i] & 0xFF00) >> 8);
            b[bpos + 1] = (byte) (buffer[i] & 0x00FF);
        }
        return b;
    }
}