Consolidate _stdlib_random functions (#2)

* Use the `__has_include` and `GRND_RANDOM` macros

* Use `getentropy` instead of `getrandom`

* Use `std::min` from the <algorithm> header

* Move `#if` out of the `_stdlib_random` function

* Use `getrandom` with "/dev/urandom" fallback

* Use `#pragma comment` to import "Bcrypt.lib"

* <https://docs.microsoft.com/en-us/cpp/preprocessor/comment-c-cpp>
* <https://clang.llvm.org/docs/UsersManual.html#microsoft-extensions>

* Use "/dev/urandom" instead of `SecRandomCopyBytes`

* Use `swift::StaticMutex` for shared "/dev/urandom"

* Add `getrandom_available`; use `O_CLOEXEC` flag

Add platform impl docs

Update copyrights

Fix docs

Add _stdlib_random test

Update _stdlib_random test

Add missing &

Notice about _stdlib_random

Fix docs

Guard on upperBound = 0

Test full range of 8 bit integers

Remove some gyb

Clean up integerRangeTest

Remove FixedWidthInteger constraint

Use arc4random universally

Fix randomElement

Constrain shuffle to RandomAccessCollection

warning instead of error

Move Apple's implementation

Fix failing test on 32 bit systems

Author: benrimmington

benchmark/single-source/RandomShuffle.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

benchmark/single-source/RandomValues.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

benchmark/utils/main.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

stdlib/public/SwiftShims/LibcShims.h

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

stdlib/public/core/Bool.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -87,23 +87,21 @@ public struct Bool {
     self = value
   }
 
-  /// Returns a random Boolean
+  /// Returns a random Boolean value
   ///
   /// - Parameter generator: The random number generator to use when getting a
   ///   random Boolean.
-  /// - Returns: A random Boolean.
+  /// - Returns: A random Boolean value.
   @inlinable
   public static func random<T: RandomNumberGenerator>(
     using generator: inout T
   ) -> Bool {
     return (generator.next() >> 17) & 1 == 0
   }
 
-  /// Returns a random Boolean
+  /// Returns a random Boolean value
   ///
-  /// - Parameter generator: The random number generator to use when getting a
-  ///   random Boolean.
-  /// - Returns: A random Boolean.
+  /// - Returns: A random Boolean value.
   ///
   /// This uses the standard library's default random number generator.
   @inlinable

stdlib/public/core/CMakeLists.txt

@@ -2,7 +2,7 @@
 #
 # This source file is part of the Swift.org open source project
 #
-# Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+# Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 # Licensed under Apache License v2.0 with Runtime Library Exception
 #
 # See https://swift.org/LICENSE.txt for license information
@@ -194,7 +194,6 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
   list(APPEND swift_core_link_flags "-all_load")
   list(APPEND swift_core_framework_depends Foundation)
   list(APPEND swift_core_framework_depends CoreFoundation)
-  list(APPEND swift_core_framework_depends Security)
   list(APPEND swift_core_private_link_libraries icucore)
 else()
   # With the GNU linker the equivalent of -all_load is to tell the linker
@@ -229,10 +228,6 @@ if(CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
       ${EXECINFO_LIBRARY})
 endif()
 
-if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
-  list(APPEND swift_core_link_flags "$ENV{SystemRoot}/system32/bcrypt.dll")
-endif()
-
 option(SWIFT_CHECK_ESSENTIAL_STDLIB
     "Check core standard library layering by linking its essential subset"
     FALSE)

stdlib/public/core/Collection.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -803,6 +803,25 @@ public protocol Collection: Sequence where SubSequence: Collection {
   ///   `endIndex`.
   func formIndex(after i: inout Index)
 
+  /// Returns a random element of the collection, using the given generator as
+  /// a source for randomness.
+  ///
+  /// You use this method to select a random element from a collection when you
+  /// are using a custom random number generator. For example, call
+  /// `randomElement(using:)` to select a random element from an array of names.
+  ///
+  ///     let names = ["Zoey", "Chloe", "Amani", "Amaia"]
+  ///     let randomName = names.randomElement(using: &myGenerator)!
+  ///     // randomName == "Amani" (maybe)
+  ///
+  /// - Parameter generator: The random number generator to use when choosing
+  ///   a random element.
+  /// - Returns: A random element from the collection. If the collection is
+  ///   empty, the method returns `nil`.
+  func randomElement<T: RandomNumberGenerator>(
+    using generator: inout T
+  ) -> Element?
+
   @available(*, deprecated, message: "all index distances are now of type Int")
   typealias IndexDistance = Int
 }
@@ -1038,9 +1057,8 @@ extension Collection {
     guard !isEmpty else { return nil }
     let random = generator.next(upperBound: UInt(count))
     let index = self.index(
-      self.startIndex,
-      offsetBy: IndexDistance(random),
-      limitedBy: self.endIndex
+      startIndex,
+      offsetBy: numericCast(random)
     )
     return self[index]
   }

stdlib/public/core/CollectionAlgorithms.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -411,8 +411,6 @@ extension Sequence {
   /// to `numbers.shuffled()` above is equivalent to calling
   /// `numbers.shuffled(using: &Random.default)`.
   ///
-  /// - Parameter generator: The random number generator to use when shuffling
-  ///   the sequence.
   /// - Returns: A shuffled array of this sequence's elements.
   ///
   /// - Complexity: O(*n*)
@@ -422,7 +420,7 @@ extension Sequence {
   }
 }
 
-extension MutableCollection {
+extension MutableCollection where Self : RandomAccessCollection {
   /// Shuffles the collection in place, using the given generator as a source
   /// for randomness.
   ///
@@ -442,6 +440,7 @@ extension MutableCollection {
   public mutating func shuffle<T: RandomNumberGenerator>(
     using generator: inout T
   ) {
+    let count = self.count
     guard count > 1 else { return }
     var amount = count
     var currentIndex = startIndex

stdlib/public/core/FloatingPoint.swift.gyb

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -2403,7 +2403,7 @@ extension BinaryFloatingPoint {
 %   exampleRange = '10.0..<20.0' if Range == 'Range' else '10.0...20.0'
 extension BinaryFloatingPoint
 where Self.RawSignificand : FixedWidthInteger,
-      Self.RawSignificand.Stride : SignedInteger & FixedWidthInteger,
+      Self.RawSignificand.Stride : SignedInteger,
       Self.RawSignificand.Magnitude : UnsignedInteger {
 
   /// Returns a random value within the specified range, using the given
@@ -2420,7 +2420,7 @@ where Self.RawSignificand : FixedWidthInteger,
   ///     // Prints "14.2286325689993"
   ///     // Prints "13.1485686260762"
   ///
-  /// The `random(using:)` static method chooses a random value from a
+  /// The `random(in:using:)` static method chooses a random value from a
   /// continuous uniform distribution in `range`, and then converts that value
   /// to the nearest representable value in this type. Depending on the size and
   /// span of `range`, some concrete values may be represented more frequently
@@ -2439,12 +2439,10 @@ where Self.RawSignificand : FixedWidthInteger,
     in range: ${Range}<Self>,
     using generator: inout T
   ) -> Self {
-%   if 'Closed' not in Range:
     _precondition(
-      range.lowerBound != range.upperBound,
-      "Can't get random value with lowerBound == upperBound"
+      !range.isEmpty,
+      "Can't get random value with an empty range"
     )
-%   end
     let delta = range.upperBound - range.lowerBound
     let rand: Self.RawSignificand
     if Self.RawSignificand.bitWidth == Self.significandBitCount + 1 {
@@ -2456,7 +2454,8 @@ where Self.RawSignificand : FixedWidthInteger,
       }
 %     end
     } else {
-      let maxSignificand = Self.RawSignificand(1 << (Self.significandBitCount + 1))
+      let significandCount = Self.significandBitCount + 1
+      let maxSignificand: Self.RawSignificand = 1 << significandCount
 %     if 'Closed' not in Range:
       rand = generator.next(upperBound: maxSignificand)
 %     else:

stdlib/public/core/Integers.swift.gyb

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -2560,11 +2560,9 @@ extension ${Range}
   public func randomElement<T: RandomNumberGenerator>(
     using generator: inout T
   ) -> Element? {
-%   if 'Closed' not in Range:
-    guard lowerBound != upperBound else {
+    guard !isEmpty else {
       return nil
     }
-%   end
     let isLowerNegative = Bound.isSigned && lowerBound < 0
     let sameSign = !Bound.isSigned || isLowerNegative == (upperBound < 0)
 %   if 'Closed' not in Range:
@@ -2658,12 +2656,10 @@ where Self.Stride : SignedInteger,
     in range: ${Range}<Self>,
     using generator: inout T
   ) -> Self {
-%   if 'Closed' not in Range:
     _precondition(
-      range.lowerBound != range.upperBound,
-      "Can't get random value with lowerBound == upperBound"
+      !range.isEmpty,
+      "Can't get random value with an empty range"
     )
-%   end
     return range.randomElement(using: &generator)!
   }
   

stdlib/public/core/Random.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -32,7 +32,7 @@ import SwiftShims
 ///         }
 ///
 ///         static func randomWeekday() -> Weekday {
-///             return Weekday.randomWeekday(using: Random.default)
+///             return Weekday.randomWeekday(using: &Random.default)
 ///         }
 ///     }
 ///
@@ -64,7 +64,7 @@ extension RandomNumberGenerator {
   @inlinable
   public mutating func next<T: FixedWidthInteger & UnsignedInteger>() -> T {
     if T.bitWidth <= UInt64.bitWidth {
-      return T(truncatingIfNeeded: self.next())
+      return T(truncatingIfNeeded: next())
     }
 
     let (quotient, remainder) = T.bitWidth.quotientAndRemainder(
@@ -73,11 +73,11 @@ extension RandomNumberGenerator {
     var tmp: T = 0
 
     for i in 0 ..< quotient {
-      tmp += T(truncatingIfNeeded: self.next()) &<< (UInt64.bitWidth * i)
+      tmp += T(truncatingIfNeeded: next()) &<< (UInt64.bitWidth * i)
     }
 
     if remainder != 0 {
-      let random = self.next()
+      let random = next()
       let mask = UInt64.max &>> (UInt64.bitWidth - remainder)
       tmp += T(truncatingIfNeeded: random & mask) &<< (UInt64.bitWidth * quotient)
     }
@@ -94,12 +94,13 @@ extension RandomNumberGenerator {
   public mutating func next<T: FixedWidthInteger & UnsignedInteger>(
     upperBound: T
   ) -> T {
+    guard upperBound != 0 else { return 0 }
     let tmp = (T.max % upperBound) + 1
     let range = tmp == upperBound ? 0 : tmp
     var random: T = 0
 
     repeat {
-      random = self.next()
+      random = next()
     } while random < range
 
     return random % upperBound
@@ -118,8 +119,18 @@ extension RandomNumberGenerator {
 ///
 /// `Random.default` is safe to use in multiple threads, and uses a
 /// cryptographically secure algorithm whenever possible.
+///
+/// Platform Implementation of `Random`
+/// ===================================
+///
+/// - Apple platforms all use `arc4random_buf(3)`.
+/// - `Linux`, `Android`, `Cygwin`, `Haiku`, `FreeBSD`, and `PS4` all try to
+///   use `getrandom(2)`, but if it doesn't exist then they read from
+///   `/dev/urandom`.
+/// - `Fuchsia` calls `getentropy(3)`.
+/// - `Windows` calls `BCryptGenRandom`.
 public struct Random : RandomNumberGenerator {
-  /// The shared, default instance of the `Range` random number generator.
+  /// The default instance of the `Random` random number generator.
   public static var `default`: Random {
     get { return Random() }
     set { /* Discard */ }
@@ -130,6 +141,7 @@ public struct Random : RandomNumberGenerator {
   /// Returns a value from a uniform, independent distribution of binary data.
   ///
   /// - Returns: An unsigned 64-bit random value.
+  @effects(releasenone)
   public mutating func next() -> UInt64 {
     var random: UInt64 = 0
     _stdlib_random(&random, MemoryLayout<UInt64>.size)
@@ -147,7 +159,7 @@ public struct Random : RandomNumberGenerator {
   }
 }
 
-public // @testable
+@usableFromInline internal// @testable
 func _stdlib_random(_ bytes: UnsafeMutableRawBufferPointer) {
   if !bytes.isEmpty {
     _stdlib_random(bytes.baseAddress!, bytes.count)