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#
#
# Nim's Runtime Library
# (c) Copyright 2012 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
## Nim types. All the procs are based on these two building blocks:
## - `!& proc <#!&>`_ used to start or mix a hash value, and
## - `!$ proc <#!$>`_ used to *finish* the hash value.
## If you want to implement hash procs for
## your custom types you will end up writing the following kind of skeleton of
## code:
##
## .. code-block:: Nim
## proc hash(x: Something): Hash =
## ## Computes a Hash from `x`.
## var h: Hash = 0
## # Iterate over parts of `x`.
## for xAtom in x:
## # Mix the atom with the partial hash.
## h = h !& xAtom
## # Finish the hash.
## result = !$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:
##
## .. code-block:: Nim
## 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 = !$h
import
strutils, etcpriv
type
Hash* = int ## a hash value; hash tables using these values should
## always have a size of a power of two and can use the ``and``
## operator instead of ``mod`` for truncation of the hash value.
{.deprecated: [THash: Hash].}
proc `!&`*(h: Hash, val: int): Hash {.inline.} =
## mixes a hash value `h` with `val` to produce a new hash value. This is
## only needed if you need to implement a hash proc for a new datatype.
result = h +% val
result = result +% result shl 10
result = result xor (result shr 6)
proc `!$`*(h: Hash): Hash {.inline.} =
## finishes the computation of the hash value. This is
## only needed if you need to implement a hash proc for a new datatype.
result = h +% h shl 3
result = result xor (result shr 11)
result = result +% result shl 15
proc hashData*(data: pointer, size: int): Hash =
## hashes an array of bytes of size `size`
var h: Hash = 0
when defined(js):
var p: cstring
asm """`p` = `Data`;"""
else:
var p = cast[cstring](data)
var i = 0
var s = size
while s > 0:
h = h !& ord(p[i])
inc(i)
dec(s)
result = !$h
when defined(js):
var objectID = 0
proc hash*(x: pointer): Hash {.inline.} =
## efficient hashing of pointers
when defined(js):
asm """
if (typeof `x` == "object") {
if ("_NimID" in `x`)
`result` = `x`["_NimID"];
else {
`result` = ++`objectID`;
`x`["_NimID"] = `result`;
}
}
"""
else:
result = (cast[Hash](x)) shr 3 # skip the alignment
when not defined(booting):
proc hash*[T: proc](x: T): Hash {.inline.} =
## efficient hashing of proc vars; closures are supported too.
when T is "closure":
result = hash(rawProc(x)) !& hash(rawEnv(x))
else:
result = hash(pointer(x))
proc hash*(x: int): Hash {.inline.} =
## efficient hashing of integers
result = x
proc hash*(x: int64): Hash {.inline.} =
## efficient hashing of int64 integers
result = toU32(x)
proc hash*(x: uint): Hash {.inline.} =
## efficient hashing of unsigned integers
result = cast[int](x)
proc hash*(x: uint64): Hash {.inline.} =
## efficient hashing of uint64 integers
result = toU32(cast[int](x))
proc hash*(x: char): Hash {.inline.} =
## efficient hashing of characters
result = ord(x)
proc hash*[T: Ordinal](x: T): Hash {.inline.} =
## efficient hashing of other ordinal types (e.g., enums)
result = ord(x)
proc hash*(x: string): Hash =
## efficient hashing of strings
var h: Hash = 0
for i in 0..x.len-1:
h = h !& ord(x[i])
result = !$h
proc hash*(x: cstring): Hash =
## efficient hashing of null-terminated strings
var h: Hash = 0
var i = 0
while x[i] != 0.char:
h = h !& ord(x[i])
inc i
result = !$h
proc hash*(sBuf: string, sPos, ePos: int): Hash =
## efficient hashing of a string buffer, from starting
## position `sPos` to ending position `ePos`
##
## ``hash(myStr, 0, myStr.high)`` is equivalent to ``hash(myStr)``
var h: Hash = 0
for i in sPos..ePos:
h = h !& ord(sBuf[i])
result = !$h
proc hashIgnoreStyle*(x: string): Hash =
## efficient hashing of strings; style is ignored
var h: Hash = 0
var i = 0
let xLen = x.len
while i < xLen:
var c = x[i]
if c == '_':
inc(i)
elif isMagicIdentSeparatorRune(cstring(x), i):
inc(i, magicIdentSeparatorRuneByteWidth)
else:
if c in {'A'..'Z'}:
c = chr(ord(c) + (ord('a') - ord('A'))) # toLower()
h = h !& ord(c)
inc(i)
result = !$h
proc hashIgnoreStyle*(sBuf: string, sPos, ePos: int): Hash =
## efficient hashing of a string buffer, from starting
## position `sPos` to ending position `ePos`; style is ignored
##
## ``hashIgnoreStyle(myBuf, 0, myBuf.high)`` is equivalent
## to ``hashIgnoreStyle(myBuf)``
var h: Hash = 0
var i = sPos
while i <= ePos:
var c = sBuf[i]
if c == '_':
inc(i)
elif isMagicIdentSeparatorRune(cstring(sBuf), i):
inc(i, magicIdentSeparatorRuneByteWidth)
else:
if c in {'A'..'Z'}:
c = chr(ord(c) + (ord('a') - ord('A'))) # toLower()
h = h !& ord(c)
inc(i)
result = !$h
proc hashIgnoreCase*(x: string): Hash =
## efficient hashing of strings; case is ignored
var h: Hash = 0
for i in 0..x.len-1:
var c = x[i]
if c in {'A'..'Z'}:
c = chr(ord(c) + (ord('a') - ord('A'))) # toLower()
h = h !& ord(c)
result = !$h
proc hashIgnoreCase*(sBuf: string, sPos, ePos: int): Hash =
## efficient hashing of a string buffer, from starting
## position `sPos` to ending position `ePos`; case is ignored
##
## ``hashIgnoreCase(myBuf, 0, myBuf.high)`` is equivalent
## to ``hashIgnoreCase(myBuf)``
var h: Hash = 0
for i in sPos..ePos:
var c = sBuf[i]
if c in {'A'..'Z'}:
c = chr(ord(c) + (ord('a') - ord('A'))) # toLower()
h = h !& ord(c)
result = !$h
proc hash*(x: float): Hash {.inline.} =
## efficient hashing of floats.
var y = x + 1.0
result = cast[ptr Hash](addr(y))[]
# Forward declarations before methods that hash containers. This allows
# containers to contain other containers
proc hash*[A](x: openArray[A]): Hash
proc hash*[A](x: set[A]): Hash
proc hash*[T: tuple](x: T): Hash =
## efficient hashing of tuples.
for f in fields(x):
result = result !& hash(f)
result = !$result
proc hash*[A](x: openArray[A]): Hash =
## efficient hashing of arrays and sequences.
for it in items(x): result = result !& hash(it)
result = !$result
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)``
for i in sPos..ePos:
result = result !& hash(aBuf[i])
result = !$result
proc hash*[A](x: set[A]): Hash =
## efficient hashing of sets.
for it in items(x): result = result !& hash(it)
result = !$result
when isMainModule:
doAssert( hash("aa bb aaaa1234") == hash("aa bb aaaa1234", 0, 13) )
doAssert( hash("aa bb aaaa1234") == hash(cstring("aa bb aaaa1234")) )
doAssert( hashIgnoreCase("aa bb aaaa1234") == hash("aa bb aaaa1234") )
doAssert( hashIgnoreStyle("aa bb aaaa1234") == hashIgnoreCase("aa bb aaaa1234") )
let xx = @['H','e','l','l','o']
let ss = "Hello"
doAssert( hash(xx) == hash(ss) )
doAssert( hash(xx) == hash(xx, 0, xx.high) )
doAssert( hash(ss) == hash(ss, 0, ss.high) )
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