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771e3db869
`$` would return a string of length 25, including the trailing null String length changed to 24, avoiding an extra null byte in the output
94 lines
2.3 KiB
Nim
94 lines
2.3 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 ``math.randomize()`` for the first call of
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## ``genOid``.
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import times, endians
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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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{.deprecated: [Toid: Oid].}
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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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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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result = newString(24)
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oidToString(oid, result)
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var
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incr: int
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fuzz: int32
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proc genOid*(): Oid =
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## generates a new OID.
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proc rand(): cint {.importc: "rand", header: "<stdlib.h>", nodecl.}
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proc gettime(dummy: ptr cint): cint {.importc: "time", header: "<time.h>".}
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proc srand(seed: cint) {.importc: "srand", header: "<stdlib.h>", nodecl.}
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var t = gettime(nil)
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var i = int32(incr)
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atomicInc(incr)
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if fuzz == 0:
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# racy, but fine semantically:
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srand(t)
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fuzz = rand()
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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 = Time(tmp)
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when isMainModule:
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let xo = genOid()
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echo xo.generatedTime
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