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594831620b
* switch from PRNG to random module
* fix the regression
* comments + tests
* runnableExamples
* make oids better
(cherry picked from commit 89a21e4ec7)
100 lines
2.7 KiB
Nim
100 lines
2.7 KiB
Nim
#
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#
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# Nim's Runtime Library
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# (c) Copyright 2013 Andreas Rumpf
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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## Nim OID support. An OID is a global ID that consists of a timestamp,
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## a unique counter and a random value. This combination should suffice to
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## produce a globally distributed unique ID. This implementation was extracted
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## from the Mongodb interface and it thus binary compatible with a Mongo OID.
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##
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## This implementation calls `initRand()` for the first call of
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## ``genOid``.
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import hashes, times, endians, random
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type
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Oid* = object ## An OID.
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time: int32 ##
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fuzz: int32 ##
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count: int32 ##
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proc `==`*(oid1: Oid, oid2: Oid): bool =
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## Compares two Mongo Object IDs for equality.
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return (oid1.time == oid2.time) and (oid1.fuzz == oid2.fuzz) and
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(oid1.count == oid2.count)
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proc hash*(oid: Oid): Hash =
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## Generates hash of Oid for use in hashtables.
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var h: Hash = 0
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h = h !& hash(oid.time)
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h = h !& hash(oid.fuzz)
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h = h !& hash(oid.count)
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result = !$h
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proc hexbyte*(hex: char): int =
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case hex
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of '0'..'9': result = (ord(hex) - ord('0'))
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of 'a'..'f': result = (ord(hex) - ord('a') + 10)
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of 'A'..'F': result = (ord(hex) - ord('A') + 10)
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else: discard
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proc parseOid*(str: cstring): Oid =
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## Parses an OID.
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var bytes = cast[cstring](addr(result.time))
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var i = 0
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while i < 12:
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bytes[i] = chr((hexbyte(str[2 * i]) shl 4) or hexbyte(str[2 * i + 1]))
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inc(i)
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proc oidToString*(oid: Oid, str: cstring) =
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## Converts an oid to `str` which must have space allocated for 25 elements.
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const hex = "0123456789abcdef"
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# work around a compiler bug:
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var str = str
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var o = oid
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var bytes = cast[cstring](addr(o))
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var i = 0
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while i < 12:
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let b = bytes[i].ord
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str[2 * i] = hex[(b and 0xF0) shr 4]
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str[2 * i + 1] = hex[b and 0xF]
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inc(i)
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str[24] = '\0'
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proc `$`*(oid: Oid): string =
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## Converts an oid to string.
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result = newString(24)
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oidToString(oid, result)
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var
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t = getTime().toUnix.int32
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seed = initRand(t)
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incr: int = seed.rand(int.high)
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let fuzz = cast[int32](seed.rand(high(int)))
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proc genOid*(): Oid =
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## Generates a new OID.
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runnableExamples:
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doAssert ($genOid()).len == 24
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if false: doAssert $genOid() == "5fc7f546ddbbc84800006aaf"
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t = getTime().toUnix.int32
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var i = cast[int32](atomicInc(incr))
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bigEndian32(addr result.time, addr(t))
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result.fuzz = fuzz
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bigEndian32(addr result.count, addr(i))
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proc generatedTime*(oid: Oid): Time =
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## Returns the generated timestamp of the OID.
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var tmp: int32
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var dummy = oid.time
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bigEndian32(addr(tmp), addr(dummy))
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result = fromUnix(tmp)
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