2.5.4Class HashBase

Base class for each hash algorithm, specialized for overloading.

Class HashBase

The HashBase class provides a set of shared interfaces that are syntactically equivalent for each specialized hash.

Hashes are generated by creating an instance of a specialized class and putting data into it. When the result is requested, a hash is finalized, which means that no more data can be added; any attempts to do so will raise an exception.

Basic usage example:

        crc = CRC32()
        > crc // prints "352441c2"

Note: Instantiating HashBase directly and calling any method will raise an error.

Overloading HashBase

To easily implement other hash algorithms in native falcon code, HashBase can be overloaded. For simplicity, only 2 methods have to be overloaded, and 2 new methods have to be added:

        class MyHash from HashBase
            state = nil // internal state
            outp = nil
            function bytes(): return 12       // must be overloaded and return a constant integer > 0
            function toMemBuf(): return self.outp  // must be overloaded and return a MemBuf with wordSize 1 and length equal to bytes()
            function process(buf)             // must be declared, as it is invoked by the module on update() calls
                // *mangle MemBuf and update state*
            function finalize()               // must be declared, as it is invoked by the module to produce the actual digest
                // *transform state and assign result MemBuf(1, bytes()) to outp*

How this works:

Note: You are strongly advised NOT to overload any other methods except the four above, unless you REALLY know what you're doing.

Advantages of doing it this way:

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