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Part of a Hash upgradability design issue proposal.

Please comment, especially on whether this seems overly baroque. --Kevin Reid 19:03, 29 August 2009 (CDT)


HashAlgorithm object protocol


Signature: run() :Tuple[OutStream[0..255], vow[Hash]]

Prepares for a hash computation. Write the data to be hashed to the returned OutStream; when it is closed the returned promise will (synchronously) resolve to the hash value.


Signature: hashSize() :Integer

Returns the number of bits in the hashes produced.


To discuss: add convenience method to hash a given List[0..255]? A given integer?


For flexibility, discoverability, and type checking benefits, hash algorithms return Hash objects which contain the bits of the hash value. All hash algorithms produce the same Hash object, but Hash objects are tagged with the algorithm that produced them.

Hash objects are Selfless. Their portrayal is [makeHash, "run", [hashAlgorithm, hashBits :List[0..255]]].

XXX What exactly is the hashAlgorithm value of a Hash? The algorithm object? A string? Must take into consideration letting them unserialize on vats that don't have the hash algorithm itself.


Signature: integer() :Integer

Returns the hash value interpreted as a big-endian unsigned integer.


Signature: octets() :List[0..255]

Returns the hash value as a list of octets.


Signature: op__cmp(other :any[Hash, any]) :comparison result XXX write spec on op__cmp and how this should be described

The comparison protocol. If the hash algorithm is the same, a lexicographic comparison of the bits, else incomparable (NaN).

XXX add method to expose hashAlgorithm

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