Changed HSTRING projection to use WindowsPreallocateStringBuffer to s…

…ave an allocation and copy.

Support/Sources/WindowsRuntime/HSTRING+methods.swift

@@ -3,12 +3,25 @@ import COM
 
 extension WindowsRuntime_ABI.SWRT_HString {
     public static func create(_ value: String) throws -> WindowsRuntime_ABI.SWRT_HString? {
-        let chars = Array(value.utf16)
-        return try chars.withUnsafeBufferPointer {
-            var result: WindowsRuntime_ABI.SWRT_HString?
-            try HResult.throwIfFailed(WindowsRuntime_ABI.SWRT_WindowsCreateString($0.baseAddress!, UInt32(chars.count), &result))
-            return result
+        if value.isEmpty { return nil }
+
+        let codeUnitCount = value.utf16.count
+
+        // Preallocate and fill a UTF-16 HSTRING_BUFFER
+        var buffer: WindowsRuntime_ABI.SWRT_HStringBuffer? = nil
+        var pointer: UnsafeMutablePointer<UInt16>? = nil
+        try HResult.throwIfFailed(WindowsRuntime_ABI.SWRT_WindowsPreallocateStringBuffer(UInt32(codeUnitCount), &pointer, &buffer))
+        guard let pointer else { throw HResult.Error.pointer }
+        _ = UnsafeMutableBufferPointer(start: pointer, count: codeUnitCount).initialize(from: value.utf16)
+
+        var result: WindowsRuntime_ABI.SWRT_HString?
+        do { try HResult.throwIfFailed(WindowsRuntime_ABI.SWRT_WindowsPromoteStringBuffer(buffer, &result)) }
+        catch {
+            WindowsRuntime_ABI.SWRT_WindowsDeleteStringBuffer(buffer)
+            throw error
         }
+
+        return result
     }
 
     public static func delete(_ value: WindowsRuntime_ABI.SWRT_HString?) {

Support/Sources/WindowsRuntime_ABI/CWinRTCore.c → Support/Sources/WindowsRuntime_ABI/Functions.c

@@ -1,4 +1,3 @@
-#include "WinRT.h"
 #include "Functions.h"
 
 #include <Windows.h>
@@ -21,14 +20,18 @@ uint32_t SWRT_SysStringLen(SWRT_BStr pbstr) {
 }
 
 #include <winstring.h>
-SWRT_HResult SWRT_WindowsCreateString(const char16_t* sourceString, uint32_t length, SWRT_HString *string) {
+SWRT_HResult SWRT_WindowsCreateString(const char16_t* sourceString, uint32_t length, SWRT_HString* string) {
     return (SWRT_HResult)WindowsCreateString((PCNZWCH)sourceString, (UINT32)length, (HSTRING*)string);
 }
 
 SWRT_HResult SWRT_WindowsDeleteString(SWRT_HString string) {
     return (SWRT_HResult)WindowsDeleteString((HSTRING)string);
 }
 
+SWRT_HResult SWRT_WindowsDeleteStringBuffer(SWRT_HStringBuffer bufferHandle) {
+    return (SWRT_HResult)WindowsDeleteStringBuffer((HSTRING_BUFFER)bufferHandle);
+}
+
 SWRT_HResult SWRT_WindowsDuplicateString(SWRT_HString string, SWRT_HString *newString) {
     return (SWRT_HResult)WindowsDuplicateString((HSTRING)string, (HSTRING*)newString);
 }
@@ -37,8 +40,16 @@ const char16_t* SWRT_WindowsGetStringRawBuffer(SWRT_HString string, uint32_t *le
     return (const char16_t*)WindowsGetStringRawBuffer((HSTRING)string, (UINT32*)length);
 }
 
+SWRT_HResult SWRT_WindowsPreallocateStringBuffer(uint32_t length, char16_t** charBuffer, SWRT_HStringBuffer* bufferHandle) {
+    return (SWRT_HResult)WindowsPreallocateStringBuffer((UINT32)length, (PWSTR*)charBuffer, (HSTRING_BUFFER*)bufferHandle);
+}
+
+SWRT_HResult SWRT_WindowsPromoteStringBuffer(SWRT_HStringBuffer bufferHandle, SWRT_HString* string) {
+    return (SWRT_HResult)WindowsPromoteStringBuffer((HSTRING_BUFFER)bufferHandle, (HSTRING*)string);
+}
+
 #include <roapi.h>
-SWRT_HResult SWRT_RoGetActivationFactory(SWRT_HString activatableClassId, SWRT_Guid* iid, void **factory) {
+SWRT_HResult SWRT_RoGetActivationFactory(SWRT_HString activatableClassId, SWRT_Guid* iid, void** factory) {
     return (SWRT_HResult)RoGetActivationFactory((HSTRING)activatableClassId, (IID*)iid, factory);
 }
 

Support/Sources/WindowsRuntime_ABI/include/Functions.h

@@ -9,18 +9,21 @@ void SWRT_SysFreeString(SWRT_BStr bstrString);
 uint32_t SWRT_SysStringLen(SWRT_BStr pbstr);
 
 // winstring.h
-SWRT_HResult SWRT_WindowsCreateString(const char16_t* sourceString, uint32_t length, SWRT_HString *string);
+SWRT_HResult SWRT_WindowsCreateString(const char16_t* sourceString, uint32_t length, SWRT_HString* string);
 SWRT_HResult SWRT_WindowsDeleteString(SWRT_HString string);
-SWRT_HResult SWRT_WindowsDuplicateString(SWRT_HString string, SWRT_HString *newString);
-const char16_t* SWRT_WindowsGetStringRawBuffer(SWRT_HString string, uint32_t *length);
+SWRT_HResult SWRT_WindowsDeleteStringBuffer(SWRT_HStringBuffer bufferHandle);
+SWRT_HResult SWRT_WindowsDuplicateString(SWRT_HString string, SWRT_HString* newString);
+const char16_t* SWRT_WindowsGetStringRawBuffer(SWRT_HString string, uint32_t* length);
+SWRT_HResult SWRT_WindowsPreallocateStringBuffer(uint32_t length, char16_t** charBuffer, SWRT_HStringBuffer* bufferHandle);
+SWRT_HResult SWRT_WindowsPromoteStringBuffer(SWRT_HStringBuffer bufferHandle, SWRT_HString* string);
 
 // roapi.h
 typedef enum SWRT_RO_INIT_TYPE {
   SWRT_RO_INIT_SINGLETHREADED = 0,
   SWRT_RO_INIT_MULTITHREADED = 1
 } SWRT_RO_INIT_TYPE;
 
-SWRT_HResult SWRT_RoGetActivationFactory(SWRT_HString activatableClassId, SWRT_Guid* iid, void **factory);
+SWRT_HResult SWRT_RoGetActivationFactory(SWRT_HString activatableClassId, SWRT_Guid* iid, void** factory);
 SWRT_HResult SWRT_RoInitialize(SWRT_RO_INIT_TYPE initType);
 void SWRT_RoUninitialize();
 

Support/Sources/WindowsRuntime_ABI/include/WinRT.h

@@ -4,9 +4,11 @@
 
 // HSTRING
 struct SWRT_HString_ {};
-
 typedef struct SWRT_HString_* SWRT_HString;
 
+struct SWRT_HStringBuffer_ {};
+typedef struct SWRT_HStringBuffer_* SWRT_HStringBuffer;
+
 // TrustLevel
 typedef int32_t SWRT_TrustLevel;
 

Support/Tests/HStringTests.swift

@@ -0,0 +1,22 @@
+import XCTest
+import WindowsRuntime
+
+internal final class HStringTests: XCTestCase {
+    func testEmptyString() throws {
+        XCTAssertNil(try HStringProjection.toABI(""))
+        XCTAssertEqual(HStringProjection.toSwift(nil), "")
+    }
+
+    func testRoundTrip() throws {
+        func assertRoundTrip(_ str: String) throws{
+            var abi = try HStringProjection.toABI(str)
+            let roundtripped = HStringProjection.toSwift(consuming: &abi)
+            XCTAssertEqual(str, roundtripped)
+        }
+
+        try assertRoundTrip("")
+        try assertRoundTrip("a")
+        try assertRoundTrip("à")
+        try assertRoundTrip("☃")
+    }
+}