add posix time formatting

Sources/POSIX/Error.swift

@@ -33,6 +33,10 @@ public enum SystemError: ErrorProtocol {
     case symlinkat(Int32, String)
     case unlink(Int32, String)
     case waitpid(Int32)
+    case time(Int32)
+    case gmtime_r(Int32)
+    case ctime_r(Int32)
+    case strftime
 }
 
 import func libc.strerror
@@ -96,6 +100,14 @@ extension SystemError: CustomStringConvertible {
             return "unlink error: \(strerror(errno)): \(path)"
         case waitpid(let errno):
             return "waitpid error: \(strerror(errno))"
+        case time(let errno):
+            return "time error: \(strerror(errno))"
+        case gmtime_r(let errno):
+            return "gmtime_r error: \(strerror(errno))"
+        case ctime_r(let errno):
+            return "ctime_r error: \(strerror(errno))"
+        case strftime:
+            return "strftime error."
         }
     }
 }

Sources/POSIX/ctime_r.swift

@@ -0,0 +1,27 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright 2015 - 2016 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See http://swift.org/LICENSE.txt for license information
+ See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+import func libc.ctime_r
+import var libc.errno
+
+public func ctime_r() throws -> String {
+    // The string result that is produced by the ctime_r() function contains exactly 26 characters.
+    let buffer = UnsafeMutablePointer<Int8>(allocatingCapacity: 50)
+    defer {
+        buffer.deallocateCapacity(50)
+    }
+    var t = try time()
+    let result = libc.ctime_r(&t, buffer)
+    guard result != nil else {
+        throw SystemError.ctime_r(errno)
+    }
+
+    return String(cString: result)
+}

Sources/POSIX/gmtime_r.swift

@@ -0,0 +1,25 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright 2015 - 2016 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See http://swift.org/LICENSE.txt for license information
+ See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+import func libc.gmtime_r
+import struct libc.tm
+import struct libc.time_t
+import var libc.errno
+
+public func gmtime_r() throws -> tm {
+    var t = try time()
+    var tmTime: tm = tm()
+    let result = libc.gmtime_r(&t, &tmTime)
+    guard result != nil else {
+        throw SystemError.gmtime_r(errno)
+    }
+
+    return tmTime
+}

Sources/POSIX/strftime.swift

@@ -0,0 +1,26 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright 2015 - 2016 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See http://swift.org/LICENSE.txt for license information
+ See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+import func libc.strftime
+import struct libc.tm
+
+public func strftime(format: String, time: tm) throws -> String {
+    let resultSize = format.characters.count + 200
+    let result = UnsafeMutablePointer<Int8>(allocatingCapacity: resultSize)
+    defer {
+        result.deallocateCapacity(resultSize)
+    }
+    var time = time
+    guard libc.strftime(result, resultSize, format, &time) != 0 else {
+        throw SystemError.strftime
+    }
+
+    return String(cString: result)
+}

Sources/POSIX/time.swift

@@ -0,0 +1,21 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright 2015 - 2016 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See http://swift.org/LICENSE.txt for license information
+ See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+import func libc.time
+import typealias libc.time_t
+import var libc.errno
+
+public func time() throws -> time_t {
+    let time = libc.time(nil)
+    guard time != -1 else {
+        throw SystemError.time(errno)
+    }
+    return time
+}