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#
#
# Nim's Runtime Library
# (c) Copyright 2013 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## Nim OID support. An OID is a global ID that consists of a timestamp,
## a unique counter and a random value. This combination should suffice to
## produce a globally distributed unique ID. This implementation was extracted
## from the Mongodb interface and it thus binary compatible with a Mongo OID.
##
## This implementation calls ``math.randomize()`` for the first call of
## ``genOid``.
import times, endians
type
Oid* = object ## an OID
time: int32 ##
fuzz: int32 ##
count: int32 ##
proc `==`*(oid1: Oid, oid2: Oid): bool =
## Compare two Mongo Object IDs for equality
return (oid1.time == oid2.time) and (oid1.fuzz == oid2.fuzz) and (oid1.count == oid2.count)
proc hexbyte*(hex: char): int =
case hex
of '0'..'9': result = (ord(hex) - ord('0'))
of 'a'..'f': result = (ord(hex) - ord('a') + 10)
of 'A'..'F': result = (ord(hex) - ord('A') + 10)
else: discard
proc parseOid*(str: cstring): Oid =
## parses an OID.
var bytes = cast[cstring](addr(result.time))
var i = 0
while i < 12:
bytes[i] = chr((hexbyte(str[2 * i]) shl 4) or hexbyte(str[2 * i + 1]))
inc(i)
proc oidToString*(oid: Oid, str: cstring) =
const hex = "0123456789abcdef"
# work around a compiler bug:
var str = str
var o = oid
var bytes = cast[cstring](addr(o))
var i = 0
while i < 12:
let b = bytes[i].ord
str[2 * i] = hex[(b and 0xF0) shr 4]
str[2 * i + 1] = hex[b and 0xF]
inc(i)
str[24] = '\0'
proc `$`*(oid: Oid): string =
result = newString(24)
oidToString(oid, result)
proc rand(): cint {.importc: "rand", header: "<stdlib.h>", nodecl.}
proc srand(seed: cint) {.importc: "srand", header: "<stdlib.h>", nodecl.}
var t = getTime().toUnix.int32
srand(t)
var
incr: int = rand()
fuzz: int32 = rand()
proc genOid*(): Oid =
## generates a new OID.
t = getTime().toUnix.int32
var i = int32(atomicInc(incr))
bigEndian32(addr result.time, addr(t))
result.fuzz = fuzz
bigEndian32(addr result.count, addr(i))
proc generatedTime*(oid: Oid): Time =
## returns the generated timestamp of the OID.
var tmp: int32
var dummy = oid.time
bigEndian32(addr(tmp), addr(dummy))
result = fromUnix(tmp)
when not defined(testing) and isMainModule:
let xo = genOid()
echo xo.generatedTime
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