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feat: add MSET "hashing" function spec #272
feat: add MSET "hashing" function spec #272
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MSET is a "hashing" function that encode repating sets of bytes
The name is inspired by the memset function.
It is similar to identity as it isn't a hash, but a complete representation of the data.
The main goal of MSET is not to be used for effective data compression. The goal is instead to compress the trivial cases of data padding.
Digest decoding
First, you read a varuint, this is the number of time the pattern must be repeated minus two (so you add two to get the true value).
Everything left in your buffer is the pattern to repeat.
If there is nothing left in the buffer (that mean that the count is the ONLY thing in the digest), then the pattern is
0x00
.The varuint count MUST be minimal and complete, if it's not that an invalid MSET hash.
The pattern size SHOULD be a power of two (implementations could likely use faster vectorized loops then).
Examples
0x0242
->0x42424242
; repeat auint8
equal to0x42
4 times0x001234
->0x12341234
; repeat auint16
equal to0x1234
2 times0x7e42
->0x42 * 128
; repeat auint8
equal to0x42
128 times0x7f1234
->0x1234 * 129
; repeat auint16
equal to0x1234
129 times0x800242
->0x42 * 256
; repeat auint8
equal to0x42
258 times0x01123456
->0x123456123456123456
; repeat auint24
equal to0x123456123456123456
3 times0x03
->0x0000000000
; zerofill 5 bytes.Rational