Implement projection caching (incomplete)

Generator/InteropTests/WinRTComponent/Clear-PEDateTimeStamp.ps1

@@ -0,0 +1,19 @@
+[CmdletBinding(PositionalBinding=$false)]
+param(
+    [Parameter(Mandatory=$true)]
+    [string] $In,
+    [Parameter(Mandatory=$true)]
+    [string] $Out
+)
+
+$ErrorActionPreference = "Stop"
+
+$PEBytes = [IO.File]::ReadAllBytes($In)
+$MSDosSignature = [BitConverter]::ToUInt16($PEBytes, 0x0)
+if ($MSDosSignature -ne 0x5A4D) { throw "Invalid MS-DOS signature" } # "MZ", little endian
+$PEHeaderOffset = [BitConverter]::ToInt32($PEBytes, 0x3C)
+$PESignature = [BitConverter]::ToInt32($PEBytes, $PEHeaderOffset)
+if ($PESignature -ne 0x4550) { throw "Invalid PE signature" } # "PE\0\0", little endian
+$PETimeDateStampOffset = $PEHeaderOffset + 0x8
+[Array]::Clear($PEBytes, $PETimeDateStampOffset, 0x4)
+[IO.File]::WriteAllBytes($Out, $PEBytes)

Generator/InteropTests/WinRTComponent/GenerateProjection.cmake

@@ -19,17 +19,39 @@ function(generate_projection)
         message(FATAL_ERROR "PROJECTION_DIR argument is required")
     endif()
 
+    string(REPLACE "\\" "" WINDOWS_SDK_VERSION "$ENV{WindowsSDKVersion}") # Remove trailing slash
+
     # Determine the support package directory
     execute_process(
         COMMAND git.exe -C "${CMAKE_CURRENT_SOURCE_DIR}" rev-parse --path-format=absolute --show-toplevel
-        OUTPUT_VARIABLE REPO_ROOT
+        OUTPUT_VARIABLE SPM_SUPPORT_PACKAGE_DIR
         OUTPUT_STRIP_TRAILING_WHITESPACE
         COMMAND_ERROR_IS_FATAL ANY)
 
+    # Skip if the inputs have not changed
+    file(SHA256 "${ARG_SWIFTWINRT_EXE}" SWIFTWINRT_EXE_HASH)
+    file(SHA256 "${ARG_WINRTCOMPONENT_WINMD}" WINRTCOMPONENT_WINMD_HASH)
+    file(SHA256 "${ARG_PROJECTION_JSON}" PROJECTION_JSON_HASH)
+    set(CACHE_KEY
+        "SwiftWinRT.exe: ${SWIFTWINRT_EXE_HASH}"
+        "WinRTComponent.winmd: ${WINRTCOMPONENT_WINMD_HASH}"
+        "Projection.json: ${PROJECTION_JSON_HASH}"
+        "Projection directory: ${ARG_PROJECTION_DIR}"
+        "Support package directory: ${SPM_SUPPORT_PACKAGE_DIR}"
+        "Windows SDK version: ${WINDOWS_SDK_VERSION}")
+    string(REPLACE ";" "\n" CACHE_KEY "${CACHE_KEY}")
+    if(EXISTS "${CMAKE_CURRENT_BINARY_DIR}/ProjectionCacheKey.txt")
+        file(READ "${CMAKE_CURRENT_BINARY_DIR}/ProjectionCacheKey.txt" PREVIOUS_CACHE_KEY)
+        if("${PREVIOUS_CACHE_KEY}" STREQUAL "${CACHE_KEY}")
+            message(STATUS "Skipping projection generation because the inputs have not changed")
+            return()
+        endif()
+    endif()
+
+    # Generate the projection
     cmake_path(CONVERT "${ARG_PROJECTION_JSON}" TO_NATIVE_PATH_LIST PROJECTION_JSON_NATIVE)
-    string(REPLACE "\\" "" WINDOWS_SDK_VERSION "$ENV{WindowsSDKVersion}") # Remove trailing slash
     cmake_path(CONVERT "${ARG_WINRTCOMPONENT_WINMD}" TO_NATIVE_PATH_LIST WINRTCOMPONENT_WINMD_NATIVE)
-    cmake_path(CONVERT "${REPO_ROOT}" TO_NATIVE_PATH_LIST SPM_SUPPORT_PACKAGE_DIR_NATIVE)
+    cmake_path(CONVERT "${SPM_SUPPORT_PACKAGE_DIR}" TO_NATIVE_PATH_LIST SPM_SUPPORT_PACKAGE_DIR_NATIVE)
     cmake_path(CONVERT "${ARG_PROJECTION_DIR}" TO_NATIVE_PATH_LIST PROJECTION_DIR_NATIVE)
     execute_process(
         COMMAND "${ARG_SWIFTWINRT_EXE}"
@@ -44,6 +66,9 @@ function(generate_projection)
             --out "${PROJECTION_DIR_NATIVE}"
             --out-manifest "${PROJECTION_DIR_NATIVE}\\WinRTComponent.manifest"
         COMMAND_ERROR_IS_FATAL ANY)
+
+    # Save the cache key
+    file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/ProjectionCacheKey.txt" "${CACHE_KEY}")
 endfunction()
 
 # Support running as a script

Generator/InteropTests/WinRTComponent/GenerateWinMD.cmake

@@ -25,8 +25,16 @@ function(generate_winrtcomponent_winmd)
             /metadata_dir "${METADATA_DIR_NATIVE}"
             /reference "${FOUNDATIONCONTRACT_WINMD_NATIVE}"
             /reference "${UNIVERSALAPICONTRACT_WINMD_NATIVE}"
-            /winmd "${WINRTCOMPONENT_WINMD_NATIVE}"
+            /winmd "${WINRTCOMPONENT_WINMD_NATIVE}.timestamped"
             /header "${WINRTCOMPONENT_H_NATIVE}"
             "${WINRTCOMPONENT_IDL_NATIVE}"
         COMMAND_ERROR_IS_FATAL ANY)
+
+    # Remove the timestamp from the generated WinRTComponent.winmd file for cachability
+    # TODO: We also need to zero the random "mvid" (module version id) field of the module metadata table :/
+    execute_process(
+        COMMAND powershell.exe -File "${CMAKE_CURRENT_SOURCE_DIR}/Clear-PEDateTimeStamp.ps1"
+            -In "${WINRTCOMPONENT_WINMD_NATIVE}.timestamped"
+            -Out "${WINRTCOMPONENT_WINMD_NATIVE}"
+        COMMAND_ERROR_IS_FATAL ANY)
 endfunction()