Merge "Add binary to write basic COW" into main

fs_mgr/libsnapshot/tools/Android.bp

@@ -20,3 +20,26 @@ cc_binary {
 
     cflags: ["-Werror"],
 }
+
+
+cc_binary {
+    name: "basic_v2_cow_writer",
+    host_supported: true,
+    defaults: [
+        "fs_mgr_defaults",
+        "libsnapshot_cow_defaults",
+    ],
+
+    srcs: ["basic_v2_cow_writer.cpp"],
+
+    static_libs: [
+        "libsnapshot_cow",
+    ],
+
+    shared_libs: [
+        "libbase",
+        "liblog",
+    ],
+
+    cflags: ["-Werror"],
+}

fs_mgr/libsnapshot/tools/basic_v2_cow_writer.cpp

@@ -0,0 +1,48 @@
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <libsnapshot/cow_compress.h>
+#include <libsnapshot/cow_format.h>
+#include <libsnapshot/cow_writer.h>
+#include <filesystem>
+
+#include "android-base/unique_fd.h"
+
+using namespace android::snapshot;
+
+// This writes a simple cow v2 file in the current directory. This file will serve as testdata for
+// ensuring our v3 cow reader will be able to read a cow file created by the v2 writer.
+//
+// WARNING: We should not be overriding this test file, as it will serve as historic marker for what
+// a device with old writer_v2 will write as a cow.
+void write_cow_v2() {
+    CowOptions options;
+    options.cluster_ops = 5;
+    options.num_merge_ops = 1;
+    std::string data = "This is some data, believe it";
+    data.resize(options.block_size, '\0');
+
+    char cwd_buffer[1024];
+    size_t cwd_buffer_size = sizeof(cwd_buffer);
+
+    // Get the current working directory path.
+    char* err = getcwd(cwd_buffer, cwd_buffer_size);
+    if (!err) {
+        LOG(ERROR) << "Couldn't get current directory";
+    }
+    android::base::unique_fd fd(open(strcat(cwd_buffer, "/cow_v2"), O_CREAT | O_RDWR, 0666));
+    if (fd.get() == -1) {
+        LOG(FATAL) << "couldn't open tmp_cow";
+    }
+    std::unique_ptr<ICowWriter> writer = CreateCowWriter(2, options, std::move(fd));
+    writer->AddCopy(0, 5);
+    writer->AddRawBlocks(2, data.data(), data.size());
+    writer->AddLabel(1);
+    writer->AddXorBlocks(50, data.data(), data.size(), 24, 10);
+    writer->AddZeroBlocks(5, 10);
+    writer->AddLabel(2);
+    writer->Finalize();
+}
+
+int main() {
+    write_cow_v2();
+}