Create a NativeFilesystem implementation of ReadWriteFilesystem

Bug: b/485385998

Author: Databean

base/cvd/cuttlefish/io/BUILD.bazel

@@ -56,6 +56,21 @@ cf_cc_library(
     ],
 )
 
+cf_cc_library(
+    name = "native_filesystem",
+    srcs = ["native_filesystem.cc"],
+    hdrs = ["native_filesystem.h"],
+    deps = [
+        "//cuttlefish/common/libs/fs",
+        "//cuttlefish/io",
+        "//cuttlefish/io:filesystem",
+        "//cuttlefish/io:shared_fd",
+        "//cuttlefish/posix:strerror",
+        "//cuttlefish/result:expect",
+        "//cuttlefish/result:result_type",
+    ],
+)
+
 cf_cc_library(
     name = "shared_fd",
     srcs = ["shared_fd.cc"],

base/cvd/cuttlefish/io/native_filesystem.cc

@@ -0,0 +1,63 @@
+//
+// Copyright (C) 2026 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "cuttlefish/io/native_filesystem.h"
+
+#include <errno.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#include <string_view>
+
+#include "cuttlefish/common/libs/fs/shared_fd.h"
+#include "cuttlefish/io/shared_fd.h"
+#include "cuttlefish/posix/strerror.h"
+#include "cuttlefish/result/expect.h"
+#include "cuttlefish/result/result_type.h"
+
+namespace cuttlefish {
+
+Result<std::unique_ptr<ReaderWriterSeeker>> NativeFilesystem::CreateFile(
+    std::string_view path) {
+  SharedFD fd =
+      SharedFD::Open(std::string(path), O_CLOEXEC | O_CREAT | O_EXCL | O_RDWR);
+  CF_EXPECTF(fd->IsOpen(),
+             "Failed to open '{}' with O_CREAT | O_EXCL | O_RDWR: '{}'", path,
+             fd->StrError());
+  return std::make_unique<SharedFdIo>(fd);
+}
+
+Result<void> NativeFilesystem::DeleteFile(std::string_view path) {
+  CF_EXPECT_GE(unlink(std::string(path).c_str()), 0, StrError(errno));
+  return {};
+}
+
+Result<std::unique_ptr<ReaderSeeker>> NativeFilesystem::OpenReadOnly(
+    std::string_view path) {
+  SharedFD fd = SharedFD::Open(std::string(path), O_CLOEXEC | O_RDONLY);
+  CF_EXPECTF(fd->IsOpen(), "Failed to open '{}' with O_RDONLY: '{}'", path,
+             fd->StrError());
+  return std::make_unique<SharedFdIo>(fd);
+}
+
+Result<std::unique_ptr<ReaderWriterSeeker>> NativeFilesystem::OpenReadWrite(
+    std::string_view path) {
+  SharedFD fd = SharedFD::Open(std::string(path), O_CLOEXEC | O_RDWR);
+  CF_EXPECTF(fd->IsOpen(), "Failed to open '{}' with O_RDWR: '{}'", path,
+             fd->StrError());
+  return std::make_unique<SharedFdIo>(fd);
+}
+
+}  // namespace cuttlefish

base/cvd/cuttlefish/io/native_filesystem.h

@@ -0,0 +1,40 @@
+//
+// Copyright (C) 2026 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <stdint.h>
+
+#include "cuttlefish/io/filesystem.h"
+#include "cuttlefish/io/io.h"
+#include "cuttlefish/result/result_type.h"
+
+namespace cuttlefish {
+
+class NativeFilesystem : public ReadWriteFilesystem {
+ public:
+  Result<std::unique_ptr<ReaderSeeker>> OpenReadOnly(
+      std::string_view path) override;
+
+  Result<std::unique_ptr<ReaderWriterSeeker>> CreateFile(
+      std::string_view path) override;
+
+  Result<void> DeleteFile(std::string_view path) override;
+
+  Result<std::unique_ptr<ReaderWriterSeeker>> OpenReadWrite(
+      std::string_view path) override;
+};
+
+}  // namespace cuttlefish

base/cvd/cuttlefish/io/shared_fd.h

@@ -23,7 +23,7 @@
 
 namespace cuttlefish {
 
-class SharedFdIo : public ReaderSeeker, public WriterSeeker {
+class SharedFdIo : public ReaderWriterSeeker {
  public:
   explicit SharedFdIo(SharedFD);