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package com.keuin.kbackupfabric.backup.incremental.identifier;
import com.keuin.kbackupfabric.util.BytesUtil;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Objects;
/**
* Identifier based on sha256.
* Immutable.
*/
public class Sha256Identifier extends SingleHashIdentifier {
private static final int SHA256_LENGTH = 32;
private static final Sha256Identifier DUMMY = new Sha256Identifier(new byte[SHA256_LENGTH]); // only for using its hash method
private static final FileIdentifierProvider<Sha256Identifier> factory = Sha256Identifier::fromFile;
private static final String marker = "S2";
public static Sha256Identifier fromFile(File file) throws IOException {
if (!file.isFile()) {
throw new IllegalArgumentException("file is not a file");
}
return new Sha256Identifier(DUMMY.hash(file));
}
/**
* Load sha-256 from a named file. Only used in StorageObjectLoader.
*
* @param fileName the file name.
* @return identifier.
*/
static Sha256Identifier fromFileName(String fileName) {
if (!fileName.matches(marker + "-[0-9A-Fa-f]{32}"))
return null;
String hexString = fileName.substring(marker.length() + 1);
return new Sha256Identifier(BytesUtil.hexToBytes(hexString));
}
public static FileIdentifierProvider<Sha256Identifier> getFactory() {
return factory;
}
protected Sha256Identifier(byte[] hash) {
super(hash, marker);
Objects.requireNonNull(hash);
if (hash.length != SHA256_LENGTH) {
throw new IllegalStateException(String.format("SHA256 must be %d bytes", SHA256_LENGTH));
}
}
@Override
protected byte[] hash(File file) throws IOException {
try {
MessageDigest digest = MessageDigest.getInstance("SHA-256");
try (FileInputStream inputStream = new FileInputStream(file)) {
// This does not work. I don't know why
// FileChannel channel = inputStream.getChannel();
// ByteBuffer buffer = ByteBuffer.allocate(128);
// int readLength;
// while ((readLength = channel.read(buffer)) > 0)
// digest.update(buffer);
// This also works, without warnings
byte[] readBuffer = new byte[1024 * 1024];
int readLength;
while ((readLength = inputStream.read(readBuffer)) > 0)
digest.update(readBuffer, 0, readLength);
// The below lines also works, but the IDE will complain about the while loop
// DigestInputStream digestInputStream = new DigestInputStream(inputStream, digest);
// while(digestInputStream.read() > 0)
// ;
return digest.digest();
}
} catch (NoSuchAlgorithmException ignored) {
// this shouldn't happen
return new byte[SHA256_LENGTH];
}
}
}
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