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MurmurHash3 sealed ​

sealed class MurmurHash3

MurmurHash3 hashing utilities, ported from the Scala standard library.

Provides stable, high-quality hash functions for collections and primitive types. Used internally by ribs_core collection types to implement Object.hashCode.

Properties ​

hashCode no setter inherited ​

int get hashCode

The hash code for this object.

A hash code is a single integer which represents the state of the object that affects operator == comparisons.

All objects have hash codes. The default hash code implemented by Object represents only the identity of the object, the same way as the default operator == implementation only considers objects equal if they are identical (see identityHashCode).

If operator == is overridden to use the object state instead, the hash code must also be changed to represent that state, otherwise the object cannot be used in hash based data structures like the default Set and Map implementations.

Hash codes must be the same for objects that are equal to each other according to operator ==. The hash code of an object should only change if the object changes in a way that affects equality. There are no further requirements for the hash codes. They need not be consistent between executions of the same program and there are no distribution guarantees.

Objects that are not equal are allowed to have the same hash code. It is even technically allowed that all instances have the same hash code, but if clashes happen too often, it may reduce the efficiency of hash-based data structures like HashSet or HashMap.

If a subclass overrides hashCode, it should override the operator == operator as well to maintain consistency.

Inherited from Object.

Implementation
dart
external int get hashCode;

runtimeType no setter inherited ​

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation
dart
external Type get runtimeType;

Methods ​

noSuchMethod() inherited ​

dynamic noSuchMethod(Invocation invocation)

Invoked when a nonexistent method or property is accessed.

A dynamic member invocation can attempt to call a member which doesn't exist on the receiving object. Example:

dart
dynamic object = 1;
object.add(42); // Statically allowed, run-time error

This invalid code will invoke the noSuchMethod method of the integer 1 with an Invocation representing the .add(42) call and arguments (which then throws).

Classes can override noSuchMethod to provide custom behavior for such invalid dynamic invocations.

A class with a non-default noSuchMethod invocation can also omit implementations for members of its interface. Example:

dart
class MockList<T> implements List<T> {
  noSuchMethod(Invocation invocation) {
    log(invocation);
    super.noSuchMethod(invocation); // Will throw.
  }
}
void main() {
  MockList().add(42);
}

This code has no compile-time warnings or errors even though the MockList class has no concrete implementation of any of the List interface methods. Calls to List methods are forwarded to noSuchMethod, so this code will log an invocation similar to Invocation.method(#add, [42]) and then throw.

If a value is returned from noSuchMethod, it becomes the result of the original invocation. If the value is not of a type that can be returned by the original invocation, a type error occurs at the invocation.

The default behavior is to throw a NoSuchMethodError.

Inherited from Object.

Implementation
dart
@pragma("vm:entry-point")
@pragma("wasm:entry-point")
external dynamic noSuchMethod(Invocation invocation);

toString() inherited ​

String toString()

A string representation of this object.

Some classes have a default textual representation, often paired with a static parse function (like int.parse). These classes will provide the textual representation as their string representation.

Other classes have no meaningful textual representation that a program will care about. Such classes will typically override toString to provide useful information when inspecting the object, mainly for debugging or logging.

Inherited from Object.

Implementation
dart
external String toString();

Operators ​

operator ==() inherited ​

bool operator ==(Object other)

The equality operator.

The default behavior for all Objects is to return true if and only if this object and other are the same object.

Override this method to specify a different equality relation on a class. The overriding method must still be an equivalence relation. That is, it must be:

  • Total: It must return a boolean for all arguments. It should never throw.

  • Reflexive: For all objects o, o == o must be true.

  • Symmetric: For all objects o1 and o2, o1 == o2 and o2 == o1 must either both be true, or both be false.

  • Transitive: For all objects o1, o2, and o3, if o1 == o2 and o2 == o3 are true, then o1 == o3 must be true.

The method should also be consistent over time, so whether two objects are equal should only change if at least one of the objects was modified.

If a subclass overrides the equality operator, it should override the hashCode method as well to maintain consistency.

Inherited from Object.

Implementation
dart
external bool operator ==(Object other);

Static Properties ​

mapSeed final ​

final int mapSeed

Seed used for hashing maps.

Implementation
dart
static final mapSeed = 'Map'.hashCode;

seqSeed final ​

final int seqSeed

Seed used for hashing sequences.

Implementation
dart
static final seqSeed = 'Seq'.hashCode;

setSeed final ​

final int setSeed

Seed used for hashing sets.

Implementation
dart
static final setSeed = 'Set'.hashCode;

Static Methods ​

bytesHash() ​

int bytesHash(Uint8List data)

Returns the MurmurHash3 hash of the given byte array data.

Implementation
dart
static int bytesHash(Uint8List data) => _bytesHash(data, arraySeed);

finalizeHash() ​

int finalizeHash(int hash, int length)

Finalizes a running hash over length elements.

Must be called after all values have been mixed via mix / mixLast.

Implementation
dart
static int finalizeHash(int hash, int length) => _finalizeHash(hash, length);

listHash() ​

int listHash(IList<Object?> xs)

Returns the MurmurHash3 hash of the IList xs.

Implementation
dart
static int listHash(IList<Object?> xs) => _listHash(xs, seqSeed);

mapHash() ​

int mapHash(RMap<Object?, Object?> xs)

Returns the MurmurHash3 hash of the map xs.

Implementation
dart
static int mapHash(RMap<Object?, Object?> xs) {
  if (xs.isEmpty) {
    return _emptyMapHash;
  } else {
    var a = 0;
    var b = 0;
    var n = 0;
    var c = 1;

    var h = mapSeed;

    final it = xs.iterator;

    while (it.hasNext) {
      final kv = it.next();
      final h = _tuple2Hash(kv.$1.hashCode, kv.$2.hashCode);

      a += h;
      b ^= h;
      c *= h | 1;
      n += 1;
    }

    h = _mix(h, a);
    h = _mix(h, b);
    h = _mixLast(h, c);

    return _finalizeHash(h, n);
  }
}

mix() ​

int mix(int hash, int data)

Incorporates data into a running hash and returns the new hash.

Use this when mixing multiple values into a hash. Call finalizeHash when done.

Implementation
dart
static int mix(int hash, int data) => _mix(hash, data);

mixLast() ​

int mixLast(int hash, int data)

Like mix, but for the last element in a hash computation.

Skips the final rotation step, which can improve avalanche behaviour for the last value mixed in.

Implementation
dart
static int mixLast(int hash, int data) => _mixLast(hash, data);

rangeHash() ​

int rangeHash(int start, int step, int last)

Returns the MurmurHash3 hash of an arithmetic range with the given start, step, and last values.

Implementation
dart
static int rangeHash(int start, int step, int last) => _rangeHash(start, step, last, seqSeed);

seqHash() ​

int seqHash(RSeq<Object?> seq)

Returns the MurmurHash3 hash of the sequence seq.

Dispatches to the most efficient implementation based on the concrete sequence type.

Implementation
dart
static int seqHash(RSeq<Object?> seq) {
  return switch (seq) {
    final IndexedSeq<Object?> xs => _indexedSeqHash(xs, seqSeed),
    final IList<Object?> xs => _listHash(xs, seqSeed),
    _ => _orderedHash(seq, seqSeed),
  };
}

setHash() ​

int setHash(RSet<Object?> xs)

Returns the MurmurHash3 hash of the set xs.

Implementation
dart
static int setHash(RSet<Object?> xs) => _unorderedHash(xs, setSeed);

stringHash() ​

int stringHash(String str)

Returns the MurmurHash3 hash of str.

Implementation
dart
static int stringHash(String str) => _stringHash(str, stringSeed);

unorderedHash() ​

int unorderedHash(RIterableOnce<Object?> xs, int seed)

Returns the MurmurHash3 hash of an unordered collection xs using seed.

Element order does not affect the result, making this suitable for set-like structures.

Implementation
dart
static int unorderedHash(RIterableOnce<Object?> xs, int seed) => _unorderedHash(xs, seed);

Constants ​

arraySeed ​

const int arraySeed

Seed used for hashing array-like structures.

Implementation
dart
static const arraySeed = 0x3c074a61;

productSeed ​

const int productSeed

Seed used for hashing product types (e.g. tuples).

Implementation
dart
static const productSeed = 0xcafebabe;

stringSeed ​

const int stringSeed

Seed used for hashing strings.

Implementation
dart
static const stringSeed = 0xf7ca7fd2;