/**
* Check can write to file
*
* @param file
* @throws IOException
*/
public void precheck(File file) throws IOException {
if (!file.exists()) {
logger.severe(
ErrorMessage.GENERAL_WRITE_FAILED_BECAUSE_FILE_NOT_FOUND.getMsg(file.getName()));
throw new IOException(
ErrorMessage.GENERAL_WRITE_FAILED_BECAUSE_FILE_NOT_FOUND.getMsg(file.getName()));
}
if (!file.canWrite()) {
logger.severe(ErrorMessage.GENERAL_WRITE_FAILED.getMsg(file.getName()));
throw new IOException(ErrorMessage.GENERAL_WRITE_FAILED.getMsg(file.getName()));
}
if (file.length() <= MINIMUM_FILESIZE) {
logger.severe(
ErrorMessage.GENERAL_WRITE_FAILED_BECAUSE_FILE_IS_TOO_SMALL.getMsg(file.getName()));
throw new IOException(
ErrorMessage.GENERAL_WRITE_FAILED_BECAUSE_FILE_IS_TOO_SMALL.getMsg(file.getName()));
}
}
/**
* Calculates hash with algorithm "MD5", "SHA-1" or SHA-256". Hash is calculated EXCLUDING
* meta-data, like id3v1 or id3v2
*
* @return byte[] hash value in byte
* @param String algorithm
* @param int buffersize
* @throws IOException
* @throws InvalidAudioFrameException
* @throws NoSuchAlgorithmException
*/
public byte[] getHash(String algorithm, int bufferSize)
throws InvalidAudioFrameException, IOException, NoSuchAlgorithmException {
File mp3File = getFile();
long startByte = getMP3StartByte(mp3File);
int id3v1TagSize = 0;
if (hasID3v1Tag()) {
ID3v1Tag id1tag = getID3v1Tag();
id3v1TagSize = id1tag.getSize();
}
InputStream inStream = Files.newInputStream(Paths.get(mp3File.getAbsolutePath()));
byte[] buffer = new byte[bufferSize];
MessageDigest digest = MessageDigest.getInstance(algorithm);
inStream.skip(startByte);
int read;
long totalSize = mp3File.length() - startByte - id3v1TagSize;
int pointer = buffer.length;
while (pointer <= totalSize) {
read = inStream.read(buffer);
digest.update(buffer, 0, read);
pointer += buffer.length;
}
read = inStream.read(buffer, 0, (int) totalSize - pointer + buffer.length);
digest.update(buffer, 0, read);
byte[] hash = digest.digest();
return hash;
}