Add string array as an option for request context params for endpoint resolution

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: GitHub Action for SwiftLint
         uses: norio-nomura/action-swiftlint@3.2.1
 
@@ -125,7 +125,7 @@ jobs:
     runs-on: ubuntu-22.04 # latest
     steps:
       - name: Checkout Source
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           submodules: true
           fetch-depth: 0

Source/AwsCommonRuntimeKit/crt/Utilities.swift

@@ -88,7 +88,7 @@
 
 extension aws_byte_buf {
     func toString() -> String {
         return String(
             data: toData(),
             encoding: .utf8)!
     }
@@ -136,7 +136,7 @@
     func toOptionalString() -> String? {
         if self.len == 0 { return nil }
         let data = Data(bytesNoCopy: self.ptr, count: self.len, deallocator: .none)
         return String(data: data, encoding: .utf8)
     }
 }
 
@@ -272,3 +272,37 @@
         }
     }
 }
+
+public func scan<S: Sequence, U>(_ seq: S, _ initial: U, _ combine: (U, S.Element) -> U) -> [U] {
+    var result: [U] = []
+    result.reserveCapacity(seq.underestimatedCount)
+    var runningResult = initial
+    for element in seq {
+    runningResult = combine(runningResult, element)
+    result.append(runningResult)
+    }
+    return result
+}
+
+/// Note: this function and associated scan function above are copied verbatim from
+/// swift standard lib where its private. 
+public func withArrayOfCStrings<R>(
+    _ args: [String], _ body: ([UnsafeMutablePointer<CChar>?]) -> R
+) -> R {
+    let argsCounts = Array(args.map { $0.utf8.count + 1 })
+    let argsOffsets = [ 0 ] + scan(argsCounts, 0, +)
+    let argsBufferSize = argsOffsets.last!
+    var argsBuffer: [UInt8] = []
+    argsBuffer.reserveCapacity(argsBufferSize)
+    for arg in args {
+        argsBuffer.append(contentsOf: arg.utf8)
+        argsBuffer.append(0)
+    }
+    return argsBuffer.withUnsafeMutableBufferPointer { (argsBuffer) in
+        let ptr = UnsafeMutableRawPointer(argsBuffer.baseAddress!).bindMemory(
+        to: CChar.self, capacity: argsBuffer.count)
+        var cStrings: [UnsafeMutablePointer<CChar>?] = argsOffsets.map { ptr + $0 }
+        cStrings[cStrings.count - 1] = nil
+        return body(cStrings)
+    }
+}

Source/AwsCommonRuntimeKit/sdkutils/endpoint/EndpointsRequestContext.swift

@@ -48,6 +48,34 @@ public class EndpointsRequestContext {
         }
     }
 
+    private func withByteCursorArrayFromStringArray<R>(
+        _ arg: [String], _ body: (UnsafeMutablePointer<aws_byte_cursor>, Int) -> R) -> R {
+        withArrayOfCStrings(arg) { cStrArr in
+            var cursors = cStrArr.map { aws_byte_cursor_from_c_str($0) }
+            let len = cursors.count
+            return cursors.withUnsafeMutableBufferPointer { cursorsPtr in 
+                return body(cursorsPtr.baseAddress!, len)
+            }
+        }
+    }
+
+    /// Add a string array endpoint parameter to the request context
+    /// - Parameters:
+    ///   - name: The name of the parameter
+    ///   - value: The value of the parameter
+    public func add(name: String, value: [String]?) throws {
+        guard let value = value else {
+            return
+        }
+        if (name.withByteCursor { nameCursor in
+            withByteCursorArrayFromStringArray(value) { ptr, len in        
+                aws_endpoints_request_context_add_string_array(allocator.rawValue, rawValue, nameCursor, ptr, len)
+            }
+        }) != AWS_OP_SUCCESS {
+            throw CommonRunTimeError.crtError(.makeFromLastError())
+        }
+    }
+
     deinit {
         aws_endpoints_request_context_release(rawValue)
     }

Test/AwsCommonRuntimeKitTests/sdkutils/EndpointsRuleEngineTests.swift

@@ -282,4 +282,11 @@ class EndpointsRuleEngineTests: XCBaseTestCase {
             let _ = try! engine.resolve(context: context)
         }
     }
+
+    func testRequestContext() {
+      let context = try! EndpointsRequestContext()
+      try! context.add(name: "Region", value: "us-west-2")
+      try! context.add(name: "Boolean", value: true)
+      try! context.add(name: "StringArray", value: ["a", "b"])
+    }
 }