Contract ABI and Recursive Length Prefix made easy for the JVM. Everything heavily optimized for maximum throughput (ABI function call encoding up to 500x faster than a popular competitor. One function init plus one encode up to 50x faster ("sam(bytes,bool,uint256[])", openjdk 12.0.1)).

ABI spec: https://solidity.readthedocs.io/en/latest/abi-spec.html

RLP spec: https://github.com/ethereum/wiki/wiki/RLP

SHA-256 (headlong-1.4.7.jar): a5041b9b0030e49f6674dda42010130777d472ad9237445f877be992630307fd

Usage

ABI codec

Encoding

Function f = new Function("baz(uint32,bool)"); // canonicalizes and parses any signature automatically
Function f2 = Function.fromJson("{\"name\": \"foo\", \"type\": \"function\", \"inputs\": [ {\"name\": \"complex_nums\", \"type\": \"tuple[]\", \"components\": [ {\"name\": \"real\", \"type\": \"decimal\"}, {\"name\": \"imaginary\", \"type\": \"decimal\"} ]} ]}");

Tuple args = new Tuple(69L, true);

// Two equivalent styles:
ByteBuffer one = f.encodeCall(args);
ByteBuffer two = f.encodeCallWithArgs(69L, true);

System.out.println(Function.formatCall(one.array())); // a multi-line hex representation
System.out.println(f.decodeCall((ByteBuffer) two.flip()).equals(args));

Decoding

Function getUfixedAndString = new Function("gogo((fixed[],int8)[1][][5])", "(ufixed,string)");

Tuple decoded = getUfixedAndString.decodeReturn(
        FastHex.decode(
                "0000000000000000000000000000000000000000000000000000000000000045"
              + "0000000000000000000000000000000000000000000000000000000000000020"
              + "0000000000000000000000000000000000000000000000000000000000000004"
              + "7730307400000000000000000000000000000000000000000000000000000000"
        )
);
        
System.out.println(decoded.equals(new Tuple(new BigDecimal(BigInteger.valueOf(69L), 18), "w00t")));

RLP codec

// for an example class Student
public Student(byte[] rlp) throws DecodeException {
    RLPIterator iter = RLP_STRICT.sequenceIterator(rlp);
    
    this.name = iter.next().asString(UTF_8);
    this.gpa = iter.next().asFloat();
    this.publicKey = iter.next().data();
    this.balance = new BigDecimal(iter.next().asBigInt(), iter.next().asInt());
}

@Override
public Object[] toObjectArray() {
    return new Object[] {
            Strings.decode(name, UTF_8),
            FloatingPoint.toBytes(gpa),
            publicKey,
            balance.unscaledValue().toByteArray(),
            Integers.toBytes(balance.scale())
    };
}

@Override
public byte[] toRLP() {
    return RLPEncoder.encodeSequentially(toObjectArray());
}

Also includes a fast hex codec and an optimized Keccak implementation.

Build

Now available in Maven Central Repository.

Or build locally:

Clone the project and install to your local maven repository using gradle publishToMavenLocal or mvn install. Then you can use one of these:

implementation 'com.esaulpaugh:headlong:1.4.8-SNAPSHOT'

<dependency>
    <groupId>com.esaulpaugh</groupId>
    <artifactId>headlong</artifactId>
    <version>1.4.8-SNAPSHOT</version>
</dependency>

Alternatively:

• Run gradle build or gradle jar which output to /build/libs
• Use mvn package which outputs to /target
• Add headlong as a project dependency

Depends on gson. Tests should take less than one minute to run. Test packages require junit and spongycastle. Jar size is ~115 KB as of 06/21/19.

See the wiki for more, such as TupleTypes, packed encoding, RLP Lists, and RLP Object Notation: https://github.com/esaulpaugh/headlong/wiki

Licensed under Apache 2.0 terms