fixup! Port workerd to Windows using clang

Use SQLite system default VFS on Windows

src/workerd/util/sqlite-test.c++

@@ -181,16 +181,10 @@ KJ_TEST("SQLite backed by real disk") {
 
     {
       auto files = dir->listNames();
-#if _WIN32
-      KJ_ASSERT(files.size() == 2);
-      KJ_EXPECT(files[0] == "foo");
-      KJ_EXPECT(files[1] == "foo-wal");
-#else
       KJ_ASSERT(files.size() == 3);
       KJ_EXPECT(files[0] == "foo");
       KJ_EXPECT(files[1] == "foo-shm");
       KJ_EXPECT(files[2] == "foo-wal");
-#endif
     }
   }
 

src/workerd/util/sqlite.c++

@@ -5,7 +5,11 @@
 #include "sqlite.h"
 #include <kj/debug.h>
 
-#if !_WIN32
+#if _WIN32
+#include <kj/win32-api-version.h>
+#include <windows.h>
+#include <kj/windows-sanity.h>
+#else
 #include <unistd.h>
 #endif
 
@@ -66,13 +70,38 @@ kj::Own<T> ownSqlite(T* obj) {
   return kj::Own<T>(obj, disposer);
 }
 
+#if _WIN32
+// https://github.com/capnproto/capnproto/blob/master/c%2B%2B/src/kj/filesystem-disk-win32.c%2B%2B#L255-L269
+static kj::Path getPathFromWin32Handle(HANDLE handle) {
+  DWORD tryLen = MAX_PATH;
+  for (;;) {
+    auto temp = kj::heapArray<wchar_t>(tryLen + 1);
+    DWORD len = GetFinalPathNameByHandleW(handle, temp.begin(), tryLen, 0);
+    if (len == 0) {
+      KJ_FAIL_WIN32("GetFinalPathNameByHandleW", GetLastError());
+    }
+    if (len < temp.size()) {
+      return kj::Path::parseWin32Api(temp.slice(0, len));
+    }
+    // Try again with new length.
+    tryLen = len;
+  }
+}
+#endif
+
 }  // namespace
 
 // =======================================================================================
 
 SqliteDatabase::SqliteDatabase(const Vfs& vfs, kj::PathPtr path) {
-  SQLITE_CALL_NODB(sqlite3_open_v2(path.toString().cStr(), &db,
-                                   SQLITE_OPEN_READONLY, vfs.getName().cStr()));
+  KJ_IF_MAYBE(rootedPath, vfs.tryAppend(path)) {
+    // If we can get the path rooted in the VFS's directory, use the system's default VFS instead
+    SQLITE_CALL_NODB(sqlite3_open_v2(rootedPath->toString().cStr(), &db,
+                                    SQLITE_OPEN_READONLY, nullptr));
+  } else {
+    SQLITE_CALL_NODB(sqlite3_open_v2(path.toString().cStr(), &db,
+                                    SQLITE_OPEN_READONLY, vfs.getName().cStr()));
+  }
 }
 
 SqliteDatabase::SqliteDatabase(const Vfs& vfs, kj::PathPtr path, kj::WriteMode mode) {
@@ -88,8 +117,14 @@ SqliteDatabase::SqliteDatabase(const Vfs& vfs, kj::PathPtr path, kj::WriteMode m
   }
   KJ_REQUIRE(kj::has(mode, kj::WriteMode::MODIFY), "SQLite doesn't support create-exclusive mode");
 
-  SQLITE_CALL_NODB(sqlite3_open_v2(path.toString().cStr(), &db,
-                                   flags, vfs.getName().cStr()));
+  KJ_IF_MAYBE(rootedPath, vfs.tryAppend(path)) {
+    // If we can get the path rooted in the VFS's directory, use the system's default VFS instead
+    SQLITE_CALL_NODB(sqlite3_open_v2(rootedPath->toString().cStr(), &db,
+                                    flags, nullptr));
+  } else {
+    SQLITE_CALL_NODB(sqlite3_open_v2(path.toString().cStr(), &db,
+                                    flags, vfs.getName().cStr()));
+  }
 }
 
 SqliteDatabase::~SqliteDatabase() noexcept(false) {
@@ -1197,6 +1232,19 @@ kj::String SqliteDatabase::Vfs::makeName() {
   return kj::str("kj-", this);
 }
 
+#if _WIN32
+kj::Maybe<kj::Path> SqliteDatabase::Vfs::tryAppend(kj::PathPtr suffix) const {
+  auto handle = KJ_UNWRAP_OR_RETURN(directory.getWin32Handle(), nullptr);
+  auto root = getPathFromWin32Handle(handle);
+  return root.append(suffix);
+}
+#else
+kj::Maybe<kj::Path> SqliteDatabase::Vfs::tryAppend(kj::PathPtr suffix) const {
+  // TODO(someday): consider implementing this on other platforms
+  return nullptr;
+}
+#endif
+
 // =======================================================================================
 
 }  // namespace workerd

src/workerd/util/sqlite.h

@@ -285,6 +285,14 @@ class SqliteDatabase::Vfs {
   // Create the value returned by `getName()`. Called once at construction time and cached in
   // `name`.
 
+  kj::Maybe<kj::Path> tryAppend(kj::PathPtr suffix) const;
+  // Tries to create a new path by appending the given path to this VFS's root directory path.
+  // This allows us to use the system's default VFS implementation, without wrapping, by passing
+  // the result of this function to sqlite3_open_v2().
+  //
+  // Unfortunately, this requires getting a file path from a kj::Directory. On Windows, we can use
+  // the GetFinalPathNameByHandleW() API. On Unix, there's no portable way to do this.
+
   friend class SqliteDatabase;
   class DefaultLockManager;
 };