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#
#
# Nimrod's Runtime Library
# (c) Copyright 2008 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## This module implements efficient computations of hash values for diverse
## Nimrod types.
import
strutils
type
THash* = int ## a hash value; hash tables using these values should
## always have a size of a power of two and can use the ``and``
## operator instead of ``mod`` for truncation of the hash value.
proc concHash(h: THash, val: int): THash {.inline.} =
result = h +% val
result = result +% result shl 10
result = result xor (result shr 6)
proc finishHash(h: THash): THash {.inline.} =
result = h +% h shl 3
result = result xor (result shr 11)
result = result +% result shl 15
proc hashData*(Data: Pointer, Size: int): THash =
## hashes an array of bytes of size `size`
var
h: THash
p: cstring
i, s: int
h = 0
p = cast[cstring](Data)
i = 0
s = size
while s > 0:
h = concHash(h, ord(p[i]))
Inc(i)
Dec(s)
result = finishHash(h)
proc hash*(x: Pointer): THash {.inline.} =
## efficient hashing of pointers
result = (cast[THash](x)) shr 3 # skip the alignment
proc hash*(x: int): THash {.inline.} =
## efficient hashing of integers
result = x
proc hash*(x: int64): THash {.inline.} =
## efficient hashing of integers
result = toU32(x)
proc hash*(x: char): THash {.inline.} =
## efficient hashing of characters
result = ord(x)
proc hash*(x: string): THash =
## efficient hashing of strings
var h: THash
h = 0
for i in 0..x.len-1:
h = concHash(h, ord(x[i]))
result = finishHash(h)
proc hashIgnoreStyle*(x: string): THash =
## efficient hashing of strings; style is ignored
var
h: THash
c: Char
h = 0
for i in 0..x.len-1:
c = x[i]
if c == '_':
continue # skip _
if c in {'A'..'Z'}:
c = chr(ord(c) + (ord('a') - ord('A'))) # toLower()
h = concHash(h, ord(c))
result = finishHash(h)
proc hashIgnoreCase*(x: string): THash =
## efficient hashing of strings; case is ignored
var
h: THash
c: Char
h = 0
for i in 0..x.len-1:
c = x[i]
if c in {'A'..'Z'}:
c = chr(ord(c) + (ord('a') - ord('A'))) # toLower()
h = concHash(h, ord(c))
result = finishHash(h)
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