Update PlatformOptions to have preferredStreamBufferSizeRange and use RangeExpression to express the various ways to configure the low and high watermark

Author: Ryan Dingman

Sources/Subprocess/Platforms/Subprocess+Darwin.swift

@@ -57,8 +57,9 @@ public struct PlatformOptions: Sendable {
     /// Creates a session and sets the process group ID
     /// i.e. Detach from the terminal.
     public var createSession: Bool = false
-    public var outputOptions: StreamOptions = .init()
-    public var errorOptions: StreamOptions = .init()
+
+    private(set) var preferredStreamBufferSizeRange: (any RangeExpression & Sendable)? = nil
+
     /// An ordered list of steps in order to tear down the child
     /// process in case the parent task is cancelled before
     /// the child proces terminates.
@@ -84,7 +85,17 @@ public struct PlatformOptions: Sendable {
             ) throws -> Void
         )? = nil
 
-    public init() {}
+    public init() {
+        self.preferredStreamBufferSizeRange = nil
+    }
+
+    public init<R>(preferredStreamBufferSizeRange: R?) where R: RangeExpression & Sendable, R.Bound == Int {
+        self.preferredStreamBufferSizeRange = preferredStreamBufferSizeRange
+    }
+
+    mutating func setPreferredStreamBufferSizeRange<R>(_ range: R?) where R: RangeExpression & Sendable, R.Bound == Int {
+        self.preferredStreamBufferSizeRange = range
+    }
 }
 
 extension PlatformOptions {
@@ -128,18 +139,6 @@ extension PlatformOptions {
     #endif
 }
 
-extension PlatformOptions {
-    public struct StreamOptions: Sendable {
-        let lowWater: Int?
-        let highWater: Int?
-
-        init(lowWater: Int? = nil, highWater: Int? = nil) {
-            self.lowWater = lowWater
-            self.highWater = highWater
-        }
-    }
-}
-
 extension PlatformOptions: CustomStringConvertible, CustomDebugStringConvertible {
     internal func description(withIndent indent: Int) -> String {
         let indent = String(repeating: " ", count: indent * 4)
@@ -369,8 +368,8 @@ extension Configuration {
                     output: output,
                     error: error,
                     inputPipe: inputPipe.createInputPipe(),
-                    outputPipe: outputPipe.createOutputPipe(with: platformOptions.outputOptions),
-                    errorPipe: errorPipe.createOutputPipe(with: platformOptions.errorOptions)
+                    outputPipe: outputPipe.createOutputPipe(with: platformOptions),
+                    errorPipe: errorPipe.createOutputPipe(with: platformOptions)
                 )
             }
 

Sources/Subprocess/Platforms/Subprocess+Linux.swift

@@ -176,8 +176,9 @@ public struct PlatformOptions: Sendable {
     // Creates a session and sets the process group ID
     // i.e. Detach from the terminal.
     public var createSession: Bool = false
-    public var outputOptions: StreamOptions = .init()
-    public var errorOptions: StreamOptions = .init()
+
+    private(set) var preferredStreamBufferSizeRange: (any RangeExpression & Sendable)? = nil
+
     /// An ordered list of steps in order to tear down the child
     /// process in case the parent task is cancelled before
     /// the child proces terminates.
@@ -196,18 +197,16 @@ public struct PlatformOptions: Sendable {
     /// call any necessary process setup functions.
     public var preSpawnProcessConfigurator: (@convention(c) @Sendable () -> Void)? = nil
 
-    public init() {}
-}
+    public init() {
+        self.preferredStreamBufferSizeRange = nil
+    }
 
-extension PlatformOptions {
-    public struct StreamOptions: Sendable {
-        let lowWater: Int?
-        let highWater: Int?
+    public init<R>(preferredStreamBufferSizeRange: R?) where R: RangeExpression & Sendable, R.Bound == Int {
+        self.preferredStreamBufferSizeRange = preferredStreamBufferSizeRange
+    }
 
-        init(lowWater: Int? = nil, highWater: Int? = nil) {
-            self.lowWater = lowWater
-            self.highWater = highWater
-        }
+    mutating func setPreferredStreamBufferSizeRange<R>(_ range: R?) where R: RangeExpression & Sendable, R.Bound == Int {
+        self.preferredStreamBufferSizeRange = range
     }
 }
 

Sources/Subprocess/Platforms/Subprocess+Unix.swift

@@ -424,7 +424,7 @@ extension CreatedPipe {
         )
     }
 
-    internal func createOutputPipe(with options: PlatformOptions.StreamOptions) -> OutputPipe {
+    internal func createOutputPipe(with options: PlatformOptions) -> OutputPipe {
         var readEnd: TrackedPlatformDiskIO? = nil
         if let readFileDescriptor = self.readFileDescriptor {
             let dispatchIO: DispatchIO = DispatchIO(
@@ -439,12 +439,22 @@ extension CreatedPipe {
                 }
             )
 
-            if let lowWater = options.lowWater {
-                dispatchIO.setLimit(lowWater: lowWater)
-            }
-
-            if let highWater = options.highWater {
-                dispatchIO.setLimit(highWater: highWater)
+            if let preferredStreamBufferSizeRange = options.preferredStreamBufferSizeRange {
+                if let range = preferredStreamBufferSizeRange as? Range<Int> {
+                    dispatchIO.setLimit(lowWater: range.lowerBound)
+                    dispatchIO.setLimit(highWater: range.upperBound)
+                } else if let range = preferredStreamBufferSizeRange as? ClosedRange<Int> {
+                    dispatchIO.setLimit(lowWater: range.lowerBound)
+                    dispatchIO.setLimit(highWater: range.upperBound)
+                } else if let range = preferredStreamBufferSizeRange as? PartialRangeFrom<Int> {
+                    dispatchIO.setLimit(lowWater: range.lowerBound)
+                } else if let range = preferredStreamBufferSizeRange as? PartialRangeUpTo<Int> {
+                    dispatchIO.setLimit(highWater: range.upperBound - 1)
+                } else if let range = preferredStreamBufferSizeRange as? PartialRangeThrough<Int> {
+                    dispatchIO.setLimit(highWater: range.upperBound)
+                } else {
+                    fatalError("Unsupported preferredStreamBufferSizeRange: \(preferredStreamBufferSizeRange)")
+                }
             }
 
             readEnd = .init(

Tests/SubprocessTests/SubprocessTests+Unix.swift

@@ -675,7 +675,7 @@ extension SubprocessUnixTests {
         """
 
         var platformOptions = PlatformOptions()
-        platformOptions.outputOptions = .init(lowWater: 0)
+        platformOptions.setPreferredStreamBufferSizeRange(0...)
 
         let start = ContinuousClock().now