Add CompositeIoTest

Bug: b/495556334

Author: Databean

base/cvd/cuttlefish/host/libs/image_aggregator/BUILD.bazel

@@ -1,6 +1,6 @@
 load("@protobuf//bazel:cc_proto_library.bzl", "cc_proto_library")
 load("@protobuf//bazel:proto_library.bzl", "proto_library")
-load("//cuttlefish/bazel:rules.bzl", "COPTS", "cf_cc_library")
+load("//cuttlefish/bazel:rules.bzl", "COPTS", "cf_cc_library", "cf_cc_test")
 
 package(
     default_visibility = ["//:android_cuttlefish"],
@@ -48,6 +48,25 @@ cf_cc_library(
     ],
 )
 
+cf_cc_test(
+    name = "composite_io_test",
+    srcs = ["composite_io_test.cc"],
+    deps = [
+        "//cuttlefish/host/libs/image_aggregator:cdisk_spec_cc_proto",
+        "//cuttlefish/host/libs/image_aggregator:composite_disk",
+        "//cuttlefish/host/libs/image_aggregator:composite_io",
+        "//cuttlefish/io",
+        "//cuttlefish/io:filesystem",
+        "//cuttlefish/io:in_memory",
+        "//cuttlefish/io:string",
+        "//cuttlefish/result:result_matchers",
+        "//cuttlefish/result:result_type",
+        "@abseil-cpp//absl/strings",
+        "@googletest//:gtest",
+        "@googletest//:gtest_main",
+    ],
+)
+
 cf_cc_library(
     name = "disk_image",
     hdrs = ["disk_image.h"],

base/cvd/cuttlefish/host/libs/image_aggregator/composite_disk.h

@@ -29,6 +29,8 @@ namespace cuttlefish {
 /** File representing a virtual disk made of separate component files.  */
 class CompositeDiskImage : public DiskImage {
  public:
+  CompositeDiskImage(CompositeDisk);
+
   static Result<CompositeDiskImage> OpenExisting(Reader&);
   static Result<CompositeDiskImage> OpenExisting(const std::string& path);
 
@@ -51,7 +53,6 @@ class CompositeDiskImage : public DiskImage {
   }
 
  private:
-  CompositeDiskImage(CompositeDisk);
   CompositeDisk cdisk_;
 };
 

base/cvd/cuttlefish/host/libs/image_aggregator/composite_io_test.cc

@@ -0,0 +1,75 @@
+//
+// 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/host/libs/image_aggregator/composite_io.h"
+
+#include <string>
+#include <string_view>
+
+#include "absl/strings/str_cat.h"
+#include "gtest/gtest.h"
+
+#include "cuttlefish/io/io.h"
+#include "cuttlefish/host/libs/image_aggregator/composite_disk.h"
+#include "cuttlefish/io/filesystem.h"
+#include "cuttlefish/io/in_memory.h"
+#include "cuttlefish/io/string.h"
+#include "cuttlefish/result/result_matchers.h"
+#include "cuttlefish/result/result_type.h"
+
+namespace cuttlefish {
+namespace {
+
+TEST(CompositeIoTest, SeekValue) {
+  std::unique_ptr<ReadWriteFilesystem> fs = InMemoryFilesystem();
+  ASSERT_NE(fs.get(), nullptr);
+
+  static constexpr std::string_view kAPath = "a";
+  static constexpr std::string_view kAContent = "hello ";
+  Result<std::unique_ptr<ReaderWriterSeeker>> file_a = fs->CreateFile(kAPath);
+  ASSERT_THAT(file_a, IsOk());
+  ASSERT_NE(file_a->get(), nullptr);
+  ASSERT_THAT(WriteString(**file_a, kAContent), IsOk());
+
+  static constexpr std::string_view kBPath = "b";
+  static constexpr std::string_view kBContent = "world";
+  Result<std::unique_ptr<ReaderWriterSeeker>> file_b = fs->CreateFile(kBPath);
+  ASSERT_THAT(file_b, IsOk());
+  ASSERT_NE(file_b->get(), nullptr);
+  ASSERT_THAT(WriteString(**file_b, kBContent), IsOk());
+
+  CompositeDisk disk;
+  disk.set_length(kAContent.size() + kBContent.size());
+
+  ComponentDisk& member_a = *disk.add_component_disks();
+  member_a.set_file_path(kAPath);
+  member_a.set_offset(0);
+
+  ComponentDisk& member_b = *disk.add_component_disks();
+  member_b.set_file_path(kBPath);
+  member_b.set_offset(kAContent.size());
+
+  CompositeDiskImage image(std::move(disk));
+
+  Result<CompositeDiskReaderIo> io =
+      CompositeDiskReaderIo::Create(std::move(image), *fs);
+  ASSERT_THAT(io, IsOk());
+
+  ASSERT_THAT(ReadToString(*io),
+              IsOkAndValue(absl::StrCat(kAContent, kBContent)));
+}
+
+}  // namespace
+}  // namespace cuttlefish