Add NewFileChecksumGenCrc32cFactory to file checksum (#6688)

Summary:
Add NewFileChecksumGenCrc32cFactory to file checksum public interface such that applications can use the build in crc32 checksum factory.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6688

Test Plan: pass make asan_check

Reviewed By: riversand963

Differential Revision: D21006859

Pulled By: zhichao-cao

fbshipit-source-id: ea8a45196a8b77c310728ab05f6cc0f49f3baef0

HISTORY.md

@@ -3,6 +3,9 @@
 ### Bug Fixes
 * Fix wrong result being read from ingested file. May happen when a key in the file happen to be prefix of another key also in the file. The issue can further cause more data corruption. The issue exists with rocksdb >= 5.0.0 since DB::IngestExternalFile() was introduced.
 
+### Public API Change
+* Add NewFileChecksumGenCrc32cFactory to the file checksum public API, such that the builtin Crc32c based file checksum generator factory can be used by applications.
+
 ### New Features
 * Added support for pipelined & parallel compression optimization for `BlockBasedTableBuilder`. This optimization makes block building, block compression and block appending a pipeline, and uses multiple threads to accelerate block compression. Users can set `CompressionOptions::parallel_threads` greater than 1 to enable compression parallelism.
 * Provide an allocator for memkind to be used with block cache. This is to work with memory technologies (Intel DCPMM is one such technology currently available) that require different libraries for allocation and management (such as PMDK and memkind). The high capacities available make it possible to provision large caches (up to several TBs in size) beyond what is achievable with DRAM.

include/rocksdb/file_checksum.h

@@ -97,4 +97,10 @@ class FileChecksumList {
 // Create a new file checksum list.
 extern FileChecksumList* NewFileChecksumList();
 
+// Return a shared_ptr of the builtin Crc32 based file checksum generatory
+// factory object, which can be shared to create the Crc32c based checksum
+// generator object.
+extern std::shared_ptr<FileChecksumGenFactory>
+GetFileChecksumGenCrc32cFactory();
+
 }  // namespace ROCKSDB_NAMESPACE

tools/ldb_cmd_test.cc

@@ -344,9 +344,7 @@ TEST_F(LdbCmdTest, DumpFileChecksumCRC32) {
   Options opts;
   opts.env = env.get();
   opts.create_if_missing = true;
-  FileChecksumGenCrc32cFactory* file_checksum_gen_factory =
-      new FileChecksumGenCrc32cFactory();
-  opts.file_checksum_gen_factory.reset(file_checksum_gen_factory);
+  opts.file_checksum_gen_factory = GetFileChecksumGenCrc32cFactory();
 
   DB* db = nullptr;
   std::string dbname = test::TmpDir();

util/file_checksum_helper.cc

@@ -77,4 +77,10 @@ FileChecksumList* NewFileChecksumList() {
   return checksum_list;
 }
 
+std::shared_ptr<FileChecksumGenFactory> GetFileChecksumGenCrc32cFactory() {
+  static std::shared_ptr<FileChecksumGenFactory> default_crc32c_gen_factory(
+      new FileChecksumGenCrc32cFactory());
+  return default_crc32c_gen_factory;
+}
+
 }  // namespace ROCKSDB_NAMESPACE