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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 is thus binary compatible with a MongoDB OID.
##
## This implementation calls `initRand()` for the first call of
## `genOid`.
import hashes, times, endians, random
from std/private/decode_helpers import handleHexChar
type
Oid* = object ## An OID.
time: int32
fuzz: int32
count: int32
proc `==`*(oid1: Oid, oid2: Oid): bool {.inline.} =
## Compares two OIDs for equality.
result = (oid1.time == oid2.time) and (oid1.fuzz == oid2.fuzz) and
(oid1.count == oid2.count)
proc hash*(oid: Oid): Hash =
## Generates the hash of an OID for use in hashtables.
var h: Hash = 0
h = h !& hash(oid.time)
h = h !& hash(oid.fuzz)
h = h !& hash(oid.count)
result = !$h
proc hexbyte*(hex: char): int {.inline.} =
result = handleHexChar(hex)
proc parseOid*(str: cstring): Oid =
## Parses an OID.
var bytes = cast[cstring](addr(result.time))
var i = 0
while i < 12:
bytes[i] = chr((hexbyte(str[2 * i]) shl 4) or hexbyte(str[2 * i + 1]))
inc(i)
template toStringImpl[T: string | cstring](result: var T, oid: Oid) =
## Stringifies `oid`.
const hex = "0123456789abcdef"
const N = 24
when T is string:
result.setLen N
var o = oid
var bytes = cast[cstring](addr(o))
var i = 0
while i < 12:
let b = bytes[i].ord
result[2 * i] = hex[(b and 0xF0) shr 4]
result[2 * i + 1] = hex[b and 0xF]
inc(i)
when T is cstring:
result[N] = '\0'
proc oidToString*(oid: Oid, str: cstring) {.deprecated: "unsafe; use `$`".} =
## Converts an oid to a string which must have space allocated for 25 elements.
# work around a compiler bug:
var str = str
toStringImpl(str, oid)
proc `$`*(oid: Oid): string =
## Converts an OID to a string.
toStringImpl(result, oid)
let
t = getTime().toUnix.int32
var
seed = initRand(t)
incr: int = seed.rand(int.high)
let fuzz = cast[int32](seed.rand(high(int)))
template genOid(result: var Oid, incr: var int, fuzz: int32) =
var time = getTime().toUnix.int32
var i = cast[int32](atomicInc(incr))
bigEndian32(addr result.time, addr(time))
result.fuzz = fuzz
bigEndian32(addr result.count, addr(i))
proc genOid*(): Oid =
## Generates a new OID.
runnableExamples:
doAssert ($genOid()).len == 24
runnableExamples("-r:off"):
echo $genOid() # for example, "5fc7f546ddbbc84800006aaf"
genOid(result, incr, fuzz)
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)
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