This module implements efficient computations of hash values for diverse Nim types. All the procs are based on these two building blocks:
If you want to implement hash procs for your custom types you will end up writing the following kind of skeleton of code:
proc hash(x: Something): Hash = ## Computes a Hash from `x`. var h: Hash = 0 # Iterate over parts of `x`. for xAtom in x: # Mix the atom with the partial hash. h = h !& xAtom # Finish the hash. result = !$h
If your custom types contain fields for which there already is a hash proc, like for example objects made up of strings
, you can simply hash together the hash value of the individual fields:
proc hash(x: Something): Hash = ## Computes a Hash from `x`. var h: Hash = 0 h = h !& hash(x.foo) h = h !& hash(x.bar) result = !$h
Hash = int
and
operator instead of mod
for truncation of the hash value. proc `!&`(h: Hash; val: int): Hash {.inline, raises: [], tags: [].}
proc `!$`(h: Hash): Hash {.inline, raises: [], tags: [].}
proc hashData(data: pointer; size: int): Hash {.raises: [], tags: [].}
proc hash(x: pointer): Hash {.inline, raises: [], tags: [].}
proc hash[T: proc](x: T): Hash {.inline.}
proc hash(x: int): Hash {.inline, raises: [], tags: [].}
proc hash(x: int64): Hash {.inline, raises: [], tags: [].}
proc hash(x: uint): Hash {.inline, raises: [], tags: [].}
proc hash(x: uint64): Hash {.inline, raises: [], tags: [].}
proc hash(x: char): Hash {.inline, raises: [], tags: [].}
proc hash[T: Ordinal](x: T): Hash {.inline.}
proc hash(x: string): Hash {.raises: [], tags: [].}
proc hash(x: cstring): Hash {.raises: [], tags: [].}
proc hash(sBuf: string; sPos, ePos: int): Hash {.raises: [], tags: [].}
efficient hashing of a string buffer, from starting position sPos to ending position ePos
hash(myStr, 0, myStr.high)
is equivalent to hash(myStr)
proc hashIgnoreStyle(x: string): Hash {.raises: [], tags: [].}
proc hashIgnoreStyle(sBuf: string; sPos, ePos: int): Hash {.raises: [], tags: [].}
efficient hashing of a string buffer, from starting position sPos to ending position ePos; style is ignored
hashIgnoreStyle(myBuf, 0, myBuf.high)
is equivalent to hashIgnoreStyle(myBuf)
proc hashIgnoreCase(x: string): Hash {.raises: [], tags: [].}
proc hashIgnoreCase(sBuf: string; sPos, ePos: int): Hash {.raises: [], tags: [].}
efficient hashing of a string buffer, from starting position sPos to ending position ePos; case is ignored
hashIgnoreCase(myBuf, 0, myBuf.high)
is equivalent to hashIgnoreCase(myBuf)
proc hash(x: float): Hash {.inline, raises: [], tags: [].}
proc hash[T: tuple](x: T): Hash
proc hash[A](x: openArray[A]): Hash
proc hash[A](aBuf: openArray[A]; sPos, ePos: int): Hash
efficient hashing of portions of arrays and sequences.
hash(myBuf, 0, myBuf.high)
is equivalent to hash(myBuf)
proc hash[A](x: set[A]): Hash
© 2006–2017 Andreas Rumpf
Licensed under the MIT License.
https://nim-lang.org/docs/hashes.html