diff --git a/.gitignore b/.gitignore
index 4532471..528610a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,3 @@
-**/uuids
-
 .vscode/.browse.*
 nimsuggest.log
 
diff --git a/README.md b/README.md
index 3b7562f..fd64a5a 100644
--- a/README.md
+++ b/README.md
@@ -7,16 +7,28 @@ API:
 type UUID* = object
   ## 128-bit UUID compliant with RFC-4122
 
+proc initUUID*(mostSigBits, leastSigBits: int64): UUID =
+  ## Initializes UUID with the specified most and least significant bits
+
+proc leastSigBits*(uuid: UUID): int64 {.inline.}
+  ## Returns 64 least significant bits of the ``uuid``
+
+proc mostSigBits*(uuid: UUID): int64 {.inline.}
+  ## Returns 64 most significant bits of the ``uuid``
+
 proc `$`*(uuid: UUID): string
-  ## Returns a string representation of the UUID in canonical form.
+  ## Returns a string representation of the ``uuid`` in canonical form.
 
 proc hash*(uuid: UUID): Hash
-  ## Computes hash of the specified UUID.
+  ## Computes hash of the specified ``uuid``.
 
 proc `==`*(x, y: UUID): bool
   ## Returns true when the specified UUIDs are equal, false otherwise.
 
-proc genUUID*(): UUID =
+proc isZero*(uuid: UUID): bool
+  ## Returns ``true`` when the ``uuid`` is zero (not set), ``false`` otherwise.
+
+proc genUUID*(): UUID
   ## Returns a random (v4) UUID.
   ## Uses a thread-local cryptographically secure PRNG (ISAAC) seeded with
   ## true random values obtained from OS.
diff --git a/src/uuids.nim b/src/uuids.nim
deleted file mode 100644
index c4690c6..0000000
--- a/src/uuids.nim
+++ /dev/null
@@ -1,87 +0,0 @@
-import strutils, hashes
-import isaac
-import urandom
-
-type
-  UUID* = object
-    ## 128-bit UUID compliant with RFC-4122
-    mostSigBits: int64
-    leastSigBits: int64
-
-template toHex(s: string, start: Natural,
-               x: BiggestInt, len: Positive) =
-  const HexChars = "0123456789abcdef"
-  var n = x
-  for j in countdown(len - 1, 0):
-    s[start + j] = HexChars[n and 0xF]
-    n = n shr 4
-    # handle negative overflow
-    if n == 0 and x < 0: n = -1
-
-proc `$`*(uuid: UUID): string =
-  ## Returns a string representation of the UUID in canonical form.
-  result = newString(36)
-  toHex(result, 0, uuid.mostSigBits shr 32, 8)
-  result[8] = '-'
-  toHex(result, 9, uuid.mostSigBits shr 16, 4)
-  result[13] = '-'
-  toHex(result, 14, uuid.mostSigBits, 4)
-  result[18] = '-'
-  toHex(result, 19, uuid.leastSigBits shr 48, 4)
-  result[23] = '-'
-  toHex(result, 24, uuid.leastSigBits, 12)
-
-proc hash*(uuid: UUID): Hash =
-  ## Computes hash of the specified UUID.
-  result = uuid.mostSigBits.hash() !& uuid.leastSigBits.hash()
-  result = !$result
-
-proc `==`*(x, y: UUID): bool =
-  ## Returns ``true`` when the specified UUIDs are equal, ``false`` otherwise.
-  x.mostSigBits == y.mostSigBits and x.leastSigBits == y.leastSigBits
-
-var rand {.threadvar.}: IsaacGenerator
-proc genUUID*(): UUID =
-  ## Returns a random (v4) UUID.
-  ## Uses a thread-local cryptographically secure PRNG (ISAAC) seeded with
-  ## true random values obtained from OS.
-  if rand == nil:
-    var seed = cast[array[256, uint32]](urandom(1024))
-    rand = newIsaacGenerator(seed)
-  result.mostSigBits = cast[int64]((rand.nextU32().uint64 shl 32) or rand.nextU32())
-  result.leastSigBits = cast[int64]((rand.nextU32().uint64 shl 32) or rand.nextU32())
-
-  # set version to 4
-  result.mostSigBits = (result.mostSigBits and 0xFFFFFFFFFFFF0FFF'i64) or
-                       0x0000000000004000'i64
-  # set IETF variant
-  result.leastSigBits = (result.leastSigBits and 0x3FFFFFFFFFFFFFFF'i64) or
-                        0x8000000000004000'i64
-
-proc parseUUID*(s: string): UUID {.raises: [ValueError].} =
-  ## Converts string representation of an UUID to UUID object.
-  ## Raises ``ValueError`` if invalid format is provided.
-  let parts = s.split('-')
-  if parts.len != 5:
-    raise newException(ValueError,
-                       "UUID must consist of 5 parts separated with `-`")
-  var mostSigBits: int64 = parseHexInt(parts[0])
-  mostSigBits = mostSigBits shl 16
-  mostSigBits = mostSigBits or parseHexInt(parts[1])
-  mostSigBits = mostSigBits shl 16
-  mostSigBits = mostSigBits or parseHexInt(parts[2])
-
-  var leastSigBits: int64 = parseHexInt(parts[3])
-  leastSigBits = leastSigBits shl 48
-  leastSigBits = leastSigBits or parseHexInt(parts[4])
-
-  result = UUID(mostSigBits: mostSigBits, leastSigBits: leastSigBits)
-
-when isMainModule:
-  let uuid = genUUID()
-  let uuidStr = $uuid
-  assert(uuidStr.len == 36)
-  assert(uuidStr[14] == '4') # version
-  assert(uuidStr[19] in {'8', '9', 'a', 'b'}) # variant (2 bits)
-  assert(uuidStr.parseUUID() == uuid)
-  assert(uuidStr.parseUUID().hash() == uuid.hash())
diff --git a/uuids.nim b/uuids.nim
new file mode 100644
index 0000000..b44ede2
--- /dev/null
+++ b/uuids.nim
@@ -0,0 +1,133 @@
+import strutils, hashes
+import isaac
+import uuids/urandom
+
+type
+  UUID* = object
+    ## 128-bit UUID compliant with RFC-4122
+    mostSigBits: int64
+    leastSigBits: int64
+
+template toHex(s: string, start: Natural,
+               x: BiggestInt, len: Positive) =
+  const HexChars = ['0', '1', '2', '3', '4', '5', '6', '7', '8',
+                    '9', 'a', 'b', 'c', 'd', 'e', 'f']
+  var n = x
+  for j in countdown(len - 1, 0):
+    s[start + j] = HexChars[int(n and 0xF)]
+    n = n shr 4
+    # handle negative overflow
+    if n == 0 and x < 0: n = -1
+
+proc uuidsParseHexInt(s: string, maxLen: int): int64 =
+  if s.len == 0:
+    raise newException(ValueError, "UUID part is empty")
+  if s.len > maxLen or s.len > sizeof(result) * 2:
+    raise newException(ValueError, "UUID part is longer than expected")
+  for c in s:
+    case c
+    of '0'..'9':
+      result = result shl 4 or (ord(c) - ord('0'))
+    of 'a'..'f':
+      result = result shl 4 or (ord(c) - ord('a') + 10)
+    of 'A'..'F':
+      result = result shl 4 or (ord(c) - ord('A') + 10)
+    else: raise newException(ValueError, "Invalid hex string: " & s)
+
+proc initUUID*(mostSigBits, leastSigBits: int64): UUID =
+  ## Initializes UUID with the specified most and least significant bits
+  result.mostSigBits = mostSigBits
+  result.leastSigBits = leastSigBits
+
+proc leastSigBits*(uuid: UUID): int64 {.inline.} =
+  ## Returns 64 least significant bits of the ``uuid``
+  uuid.leastSigBits
+
+proc mostSigBits*(uuid: UUID): int64 {.inline.} =
+  ## Returns 64 most significant bits of the ``uuid``
+  uuid.mostSigBits
+
+proc `$`*(uuid: UUID): string =
+  ## Returns a string representation of the ``uuid`` in canonical form.
+  result = newString(36)
+  toHex(result, 0, uuid.mostSigBits shr 32, 8)
+  result[8] = '-'
+  toHex(result, 9, uuid.mostSigBits shr 16, 4)
+  result[13] = '-'
+  toHex(result, 14, uuid.mostSigBits, 4)
+  result[18] = '-'
+  toHex(result, 19, uuid.leastSigBits shr 48, 4)
+  result[23] = '-'
+  toHex(result, 24, uuid.leastSigBits, 12)
+
+proc hash*(uuid: UUID): Hash =
+  ## Computes hash of the specified ``uuid``.
+  result = uuid.mostSigBits.hash() !& uuid.leastSigBits.hash()
+  result = !$result
+
+proc `==`*(x, y: UUID): bool =
+  ## Returns ``true`` when the specified UUIDs are equal, ``false`` otherwise.
+  x.mostSigBits == y.mostSigBits and x.leastSigBits == y.leastSigBits
+
+proc isZero*(uuid: UUID): bool =
+  ## Returns ``true`` when the ``uuid`` is zero (not set), ``false`` otherwise.
+  uuid.mostSigBits == 0'i64 and uuid.leastSigBits == 0'i64
+
+var rand {.threadvar.}: IsaacGenerator
+proc genUUID*(): UUID =
+  ## Returns a random (v4) UUID.
+  ## Uses a thread-local cryptographically secure PRNG (ISAAC) seeded with
+  ## true random values obtained from OS.
+  if rand == nil:
+    var seed = cast[array[256, uint32]](urandom(1024))
+    rand = newIsaacGenerator(seed)
+  result.mostSigBits = cast[int64]((rand.nextU32().uint64 shl 32) or rand.nextU32())
+  result.leastSigBits = cast[int64]((rand.nextU32().uint64 shl 32) or rand.nextU32())
+
+  # set version to 4
+  result.mostSigBits = (result.mostSigBits and 0xFFFFFFFFFFFF0FFF'i64) or
+                       0x0000000000004000'i64
+  # set IETF variant
+  result.leastSigBits = (result.leastSigBits and 0x3FFFFFFFFFFFFFFF'i64) or
+                        0x8000000000000000'i64
+
+proc parseUUID*(s: string): UUID {.raises: [ValueError].} =
+  ## Converts string representation of an UUID to UUID object.
+  ## Raises ``ValueError`` if invalid format is provided.
+  let parts = s.split('-')
+  if parts.len != 5:
+    raise newException(ValueError,
+                       "UUID must consist of 5 parts separated with `-`")
+  var mostSigBits: int64 = uuidsParseHexInt(parts[0], 8)
+  mostSigBits = mostSigBits shl 16
+  mostSigBits = mostSigBits or uuidsParseHexInt(parts[1], 4)
+  mostSigBits = mostSigBits shl 16
+  mostSigBits = mostSigBits or uuidsParseHexInt(parts[2], 4)
+
+  var leastSigBits: int64 = uuidsParseHexInt(parts[3], 4)
+  leastSigBits = leastSigBits shl 48
+  leastSigBits = leastSigBits or uuidsParseHexInt(parts[4], 12)
+
+  result = UUID(mostSigBits: mostSigBits, leastSigBits: leastSigBits)
+
+when isMainModule:
+  var uuid: UUID
+  assert(uuid.isZero())
+  for i in 1..100:
+    uuid = genUUID()
+    let uuidStr = $uuid
+    assert(uuidStr.len == 36)
+    assert(uuidStr[14] == '4') # version
+    assert(uuidStr[19] in {'8', '9', 'a', 'b'}) # variant (2 bits)
+
+    let parsedUUID = uuidStr.parseUUID()
+    assert(parsedUUID == uuid)
+    assert(parsedUUID.hash() == uuid.hash())
+    assert(mostSigBits(parsedUUID) == mostSigBits(uuid))
+    assert(leastSigBits(parsedUUID) == leastSigBits(uuid))
+
+    let newUUID = initUUID(mostSigBits(uuid), leastSigBits(uuid))
+    assert(newUUID == uuid)
+    assert(newUUID.hash() == uuid.hash())
+    assert(mostSigBits(newUUID) == mostSigBits(uuid))
+    assert(leastSigBits(newUUID) == leastSigBits(uuid))
diff --git a/uuids.nimble b/uuids.nimble
index c470a8e..ccc6e86 100644
--- a/uuids.nimble
+++ b/uuids.nimble
@@ -1,10 +1,9 @@
 [Package]
 name: "uuids"
-version: "0.1.1"
+version: "0.1.11"
 author: "Xored Software, Inc."
 description: "UUID library"
 license: "MIT"
-srcDir: "src"
 
 [Deps]
-requires: "isaac >= 0.1.0"
+requires: "isaac >= 0.1.3"
diff --git a/src/urandom.nim b/uuids/urandom.nim
similarity index 83%
rename from src/urandom.nim
rename to uuids/urandom.nim
index 25dcf9f..6078de4 100644
--- a/src/urandom.nim
+++ b/uuids/urandom.nim
@@ -5,8 +5,10 @@ when defined(windows):
 
   type ULONG_PTR = int
   type HCRYPTPROV = ULONG_PTR
-  var PROV_RSA_FULL {.importc, header: "<windows.h>".}: DWORD
-  var CRYPT_VERIFYCONTEXT {.importc, header: "<windows.h>".}: DWORD
+  var PROV_RSA_FULL {.importc, header: """#include <windows.h>
+#include <wincrypt.h>""".}: DWORD
+  var CRYPT_VERIFYCONTEXT {.importc, header: """#include <windows.h>
+#include <wincrypt.h>""".}: DWORD
 
   {.push, stdcall, dynlib: "Advapi32.dll".}
 
@@ -14,16 +16,16 @@ when defined(windows):
     proc CryptAcquireContext(
       phProv: ptr HCRYPTPROV, pszContainer: WideCString,
       pszProvider: WideCString, dwProvType: DWORD, dwFlags: DWORD
-    ): WinBool {.importc: "CryptAcquireContextW".}
+    ): WINBOOL {.importc: "CryptAcquireContextW".}
   else:
     proc CryptAcquireContext(
       phProv: ptr HCRYPTPROV, pszContainer: cstring, pszProvider: cstring,
       dwProvType: DWORD, dwFlags: DWORD
-    ): WinBool {.importc: "CryptAcquireContextA".}
+    ): WINBOOL {.importc: "CryptAcquireContextA".}
 
   proc CryptGenRandom(
     hProv: HCRYPTPROV, dwLen: DWORD, pbBuffer: pointer
-  ): WinBool {.importc: "CryptGenRandom".}
+  ): WINBOOL {.importc: "CryptGenRandom".}
 
   {.pop.}