Hash Utils

This project contains utilities to hash files with SHA256/SHA512/MD5.

The implemenation uses memory mapping of files in order to achieve a high level of performance.

Please note that the current implementation in this library requires the use of Java 21 + preview features enabled.

You can enable preview features via --enable-preview vm / compiler argument.

Maven

<dependency>
  <groupId>io.metaloom.utils</groupId>
  <artifactId>hash-utils</artifactId>
  <version>0.3.0</version>
</dependency>

Algorithms

MD5

Path path = Paths.get("pom.xml");
String hash = HashUtils.computeMD5(path);
byte[] binHash = HashUtils.computeBinMD5(path);

SHA256

Path path = Paths.get("pom.xml");
String hash = HashUtils.computeSHA256(path);
byte[] binHash = HashUtils.computeBinSHA256(path);

SHA512

Path path = Paths.get("pom.xml");
String hash = HashUtils.computeSHA512(path);
byte[] binHash = HashUtils.computeBinSHA512(path);

Chunk Hash

The chunk hash method will only hash the first 5 MB or 5% of the provided file. This method may be used when the performance / precision tradeof is acceptable.

Path path = Paths.get("pom.xml");
String hash = HashUtils.computeChunkHash(path);
byte[] binHash = HashUtils.computeBinChunkHash(path);

Zero Chunks

The zero chunk count method computes the amount of 4k byte chunks which consists of zeros.

Path path = Paths.get("pom.xml");
int count = HashUtils.computeZeroChunkCount(path);

Implementations

This project currently contains different hasher implementations:

//  Return the default hasher
Hasher hasher = DefaultHasher.getHasher();

// Or create one from a specific implementation
Hasher hasher = new FileChannelHasher();

Name	State	Description
MemorySegmentHasher	(default)	Uses the JEP 424 foreign memory allocation API to memory map files.
FileChannelHasher	-	Uses a filechannel to map regions of the file to memory. This implementation only supports files which are smaller Integer.MAX_VALUE bytes.
MmapHasher	(legacy/removed)	Uses JNI to make use of Mmap to map file regions to direct memory.

Release Process

# Update maven version to next release
mvn versions:set -DgenerateBackupPoms=false

# Now run tests locally or via GitHub actions
mvn clean package

# Deploy to maven central and auto-close staging repo. 
# Adding the property will trigger the profiles in the parent pom to include gpg,javadoc...
mvn clean deploy -Drelease