Some checksum code refactoring (#9113)

Summary:
To prepare for adding checksum to footer and "context aware"
checksums. This also brings closely related code much closer together.

Recently added `BlockBasedTableBuilder::ComputeBlockTrailer` for testing
is made obsolete in the refactoring, as testing the checksums can happen
at a lower level of abstraction.

Also now checking for unrecognized checksum type on reading footer,
rather than later on use.

Also removed an obsolete function delcaration.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9113

Test Plan:
existing tests worked before refactoring to remove
`ComputeBlockTrailer`. And then refactored+improved tests using it.

Reviewed By: mrambacher

Differential Revision: D32090149

Pulled By: pdillinger

fbshipit-source-id: 2879da683c1498ea85a3b70dace9b6d9f6b47b6e

options/options_helper.h

@@ -30,6 +30,10 @@ std::vector<CompressionType> GetSupportedDictCompressions();
 
 std::vector<ChecksumType> GetSupportedChecksums();
 
+inline bool IsSupportedChecksumType(ChecksumType type) {
+  return type >= kNoChecksum && type <= kXXH3;
+}
+
 // Checks that the combination of DBOptions and ColumnFamilyOptions are valid
 Status ValidateOptions(const DBOptions& db_opts,
                        const ColumnFamilyOptions& cf_opts);

table/block_based/block_based_table_builder.cc

@@ -49,11 +49,9 @@
 #include "table/table_builder.h"
 #include "util/coding.h"
 #include "util/compression.h"
-#include "util/crc32c.h"
 #include "util/stop_watch.h"
 #include "util/string_util.h"
 #include "util/work_queue.h"
-#include "util/xxhash.h"
 
 namespace ROCKSDB_NAMESPACE {
 
@@ -1210,60 +1208,6 @@ void BlockBasedTableBuilder::CompressAndVerifyBlock(
   }
 }
 
-void BlockBasedTableBuilder::ComputeBlockTrailer(
-    const Slice& block_contents, CompressionType compression_type,
-    ChecksumType checksum_type, std::array<char, kBlockTrailerSize>* trailer) {
-  (*trailer)[0] = compression_type;
-  uint32_t checksum = 0;
-  switch (checksum_type) {
-    case kNoChecksum:
-      break;
-    case kCRC32c: {
-      uint32_t crc =
-          crc32c::Value(block_contents.data(), block_contents.size());
-      // Extend to cover compression type
-      crc = crc32c::Extend(crc, trailer->data(), 1);
-      checksum = crc32c::Mask(crc);
-      break;
-    }
-    case kxxHash: {
-      XXH32_state_t* const state = XXH32_createState();
-      XXH32_reset(state, 0);
-      XXH32_update(state, block_contents.data(), block_contents.size());
-      // Extend to cover compression type
-      XXH32_update(state, trailer->data(), 1);
-      checksum = XXH32_digest(state);
-      XXH32_freeState(state);
-      break;
-    }
-    case kxxHash64: {
-      XXH64_state_t* const state = XXH64_createState();
-      XXH64_reset(state, 0);
-      XXH64_update(state, block_contents.data(), block_contents.size());
-      // Extend to cover compression type
-      XXH64_update(state, trailer->data(), 1);
-      checksum = Lower32of64(XXH64_digest(state));
-      XXH64_freeState(state);
-      break;
-    }
-    case kXXH3: {
-      // XXH3 is a complicated hash function that is extremely fast on
-      // contiguous input, but that makes its streaming support rather
-      // complex. It is worth custom handling of the last byte (`type`)
-      // in order to avoid allocating a large state object and bringing
-      // that code complexity into CPU working set.
-      checksum = Lower32of64(
-          XXH3_64bits(block_contents.data(), block_contents.size()));
-      checksum = ModifyChecksumForCompressionType(checksum, compression_type);
-      break;
-    }
-    default:
-      assert(false);
-      break;
-  }
-  EncodeFixed32(trailer->data() + 1, checksum);
-}
-
 void BlockBasedTableBuilder::WriteRawBlock(const Slice& block_contents,
                                            CompressionType type,
                                            BlockHandle* handle,
@@ -1281,8 +1225,12 @@ void BlockBasedTableBuilder::WriteRawBlock(const Slice& block_contents,
   io_s = r->file->Append(block_contents);
   if (io_s.ok()) {
     std::array<char, kBlockTrailerSize> trailer;
-    ComputeBlockTrailer(block_contents, type, r->table_options.checksum,
-                        &trailer);
+    trailer[0] = type;
+    uint32_t checksum = ComputeBuiltinChecksumWithLastByte(
+        r->table_options.checksum, block_contents.data(), block_contents.size(),
+        /*last_byte*/ type);
+    EncodeFixed32(trailer.data() + 1, checksum);
+
     assert(io_s.ok());
     TEST_SYNC_POINT_CALLBACK(
         "BlockBasedTableBuilder::WriteRawBlock:TamperWithChecksum",

table/block_based/block_based_table_builder.h

@@ -100,12 +100,6 @@ class BlockBasedTableBuilder : public TableBuilder {
   // Get file checksum function name
   const char* GetFileChecksumFuncName() const override;
 
-  // Computes and populates block trailer for a block
-  static void ComputeBlockTrailer(const Slice& block_contents,
-                                  CompressionType compression_type,
-                                  ChecksumType checksum_type,
-                                  std::array<char, kBlockTrailerSize>* trailer);
-
  private:
   bool ok() const { return status().ok(); }
 

table/block_based/reader_common.cc

@@ -9,12 +9,11 @@
 #include "table/block_based/reader_common.h"
 
 #include "monitoring/perf_context_imp.h"
+#include "rocksdb/table.h"
 #include "table/format.h"
 #include "util/coding.h"
 #include "util/crc32c.h"
-#include "util/hash.h"
 #include "util/string_util.h"
-#include "util/xxhash.h"
 
 namespace ROCKSDB_NAMESPACE {
 void ForceReleaseCachedEntry(void* arg, void* h) {
@@ -33,39 +32,20 @@ Status VerifyBlockChecksum(ChecksumType type, const char* data,
   // And then the stored checksum value (4 bytes).
   uint32_t stored = DecodeFixed32(data + len);
 
-  Status s;
-  uint32_t computed = 0;
-  switch (type) {
-    case kNoChecksum:
-      break;
-    case kCRC32c:
+  uint32_t computed = ComputeBuiltinChecksum(type, data, len);
+  if (stored == computed) {
+    return Status::OK();
+  } else {
+    // Unmask for people who might look for reference crc value
+    if (type == kCRC32c) {
       stored = crc32c::Unmask(stored);
-      computed = crc32c::Value(data, len);
-      break;
-    case kxxHash:
-      computed = XXH32(data, len, 0);
-      break;
-    case kxxHash64:
-      computed = Lower32of64(XXH64(data, len, 0));
-      break;
-    case kXXH3:
-      computed = Lower32of64(XXH3_64bits(data, block_size));
-      // Treat compression type separately for speed in building table files
-      computed = ModifyChecksumForCompressionType(computed, data[block_size]);
-      break;
-    default:
-      s = Status::Corruption(
-          "unknown checksum type " + ToString(type) + " from footer of " +
-          file_name + ", while checking block at offset " + ToString(offset) +
-          " size " + ToString(block_size));
+      computed = crc32c::Unmask(computed);
     }
-  if (s.ok() && stored != computed) {
-    s = Status::Corruption(
+    return Status::Corruption(
         "block checksum mismatch: stored = " + ToString(stored) +
         ", computed = " + ToString(computed) + ", type = " + ToString(type) +
         "  in " + file_name + " offset " + ToString(offset) + " size " +
         ToString(block_size));
   }
-  return s;
 }
 }  // namespace ROCKSDB_NAMESPACE

table/format.cc

@@ -17,6 +17,7 @@
 #include "memory/memory_allocator.h"
 #include "monitoring/perf_context_imp.h"
 #include "monitoring/statistics.h"
+#include "options/options_helper.h"
 #include "rocksdb/env.h"
 #include "rocksdb/options.h"
 #include "table/block_based/block.h"
@@ -25,8 +26,10 @@
 #include "util/coding.h"
 #include "util/compression.h"
 #include "util/crc32c.h"
+#include "util/hash.h"
 #include "util/stop_watch.h"
 #include "util/string_util.h"
+#include "util/xxhash.h"
 
 namespace ROCKSDB_NAMESPACE {
 
@@ -50,8 +53,8 @@ bool ShouldReportDetailedTime(Env* env, Statistics* stats) {
 
 void BlockHandle::EncodeTo(std::string* dst) const {
   // Sanity check that all fields have been set
-  assert(offset_ != ~static_cast<uint64_t>(0));
-  assert(size_ != ~static_cast<uint64_t>(0));
+  assert(offset_ != ~uint64_t{0});
+  assert(size_ != ~uint64_t{0});
   PutVarint64Varint64(dst, offset_, size_);
 }
 
@@ -245,6 +248,11 @@ Status Footer::DecodeFrom(Slice* input) {
       return Status::Corruption("bad checksum type");
     }
     checksum_ = static_cast<ChecksumType>(chksum);
+    if (chksum != static_cast<uint32_t>(checksum_) ||
+        !IsSupportedChecksumType(checksum_)) {
+      return Status::Corruption("unknown checksum type " +
+                                ROCKSDB_NAMESPACE::ToString(chksum));
+    }
   }
 
   Status result = metaindex_handle_.DecodeFrom(input);
@@ -344,6 +352,88 @@ Status ReadFooterFromFile(const IOOptions& opts, RandomAccessFileReader* file,
   return Status::OK();
 }
 
+namespace {
+// Custom handling for the last byte of a block, to avoid invoking streaming
+// API to get an effective block checksum. This function is its own inverse
+// because it uses xor.
+inline uint32_t ModifyChecksumForLastByte(uint32_t checksum, char last_byte) {
+  // This strategy bears some resemblance to extending a CRC checksum by one
+  // more byte, except we don't need to re-mix the input checksum as long as
+  // we do this step only once (per checksum).
+  const uint32_t kRandomPrime = 0x6b9083d9;
+  return checksum ^ static_cast<uint8_t>(last_byte) * kRandomPrime;
+}
+}  // namespace
+
+uint32_t ComputeBuiltinChecksum(ChecksumType type, const char* data,
+                                size_t data_size) {
+  switch (type) {
+    case kCRC32c:
+      return crc32c::Mask(crc32c::Value(data, data_size));
+    case kxxHash:
+      return XXH32(data, data_size, /*seed*/ 0);
+    case kxxHash64:
+      return Lower32of64(XXH64(data, data_size, /*seed*/ 0));
+    case kXXH3: {
+      if (data_size == 0) {
+        // Special case because of special handling for last byte, not
+        // present in this case. Can be any value different from other
+        // small input size checksums.
+        return 0;
+      } else {
+        // See corresponding code in ComputeBuiltinChecksumWithLastByte
+        uint32_t v = Lower32of64(XXH3_64bits(data, data_size - 1));
+        return ModifyChecksumForLastByte(v, data[data_size - 1]);
+      }
+    }
+    default:  // including kNoChecksum
+      return 0;
+  }
+}
+
+uint32_t ComputeBuiltinChecksumWithLastByte(ChecksumType type, const char* data,
+                                            size_t data_size, char last_byte) {
+  switch (type) {
+    case kCRC32c: {
+      uint32_t crc = crc32c::Value(data, data_size);
+      // Extend to cover last byte (compression type)
+      crc = crc32c::Extend(crc, &last_byte, 1);
+      return crc32c::Mask(crc);
+    }
+    case kxxHash: {
+      XXH32_state_t* const state = XXH32_createState();
+      XXH32_reset(state, 0);
+      XXH32_update(state, data, data_size);
+      // Extend to cover last byte (compression type)
+      XXH32_update(state, &last_byte, 1);
+      uint32_t v = XXH32_digest(state);
+      XXH32_freeState(state);
+      return v;
+    }
+    case kxxHash64: {
+      XXH64_state_t* const state = XXH64_createState();
+      XXH64_reset(state, 0);
+      XXH64_update(state, data, data_size);
+      // Extend to cover last byte (compression type)
+      XXH64_update(state, &last_byte, 1);
+      uint32_t v = Lower32of64(XXH64_digest(state));
+      XXH64_freeState(state);
+      return v;
+    }
+    case kXXH3: {
+      // XXH3 is a complicated hash function that is extremely fast on
+      // contiguous input, but that makes its streaming support rather
+      // complex. It is worth custom handling of the last byte (`type`)
+      // in order to avoid allocating a large state object and bringing
+      // that code complexity into CPU working set.
+      uint32_t v = Lower32of64(XXH3_64bits(data, data_size));
+      return ModifyChecksumForLastByte(v, last_byte);
+    }
+    default:  // including kNoChecksum
+      return 0;
+  }
+}
+
 Status UncompressBlockContentsForCompressionType(
     const UncompressionInfo& uncompression_info, const char* data, size_t n,
     BlockContents* contents, uint32_t format_version,

table/format.h

@@ -226,17 +226,16 @@ inline CompressionType get_block_compression_type(const char* block_data,
   return static_cast<CompressionType>(block_data[block_size]);
 }
 
-// Custom handling for the last byte of a block, to avoid invoking streaming
-// API to get an effective block checksum. This function is its own inverse
-// because it uses xor.
-inline uint32_t ModifyChecksumForCompressionType(uint32_t checksum,
-                                                 char compression_type) {
-  // This strategy bears some resemblance to extending a CRC checksum by one
-  // more byte, except we don't need to re-mix the input checksum as long as
-  // we do this step only once (per checksum).
-  const uint32_t kRandomPrime = 0x6b9083d9;
-  return checksum ^ static_cast<uint8_t>(compression_type) * kRandomPrime;
-}
+// Computes a checksum using the given ChecksumType. Sometimes we need to
+// include one more input byte logically at the end but not part of the main
+// data buffer. If data_size >= 1, then
+// ComputeBuiltinChecksum(type, data, size)
+// ==
+// ComputeBuiltinChecksumWithLastByte(type, data, size - 1, data[size - 1])
+uint32_t ComputeBuiltinChecksum(ChecksumType type, const char* data,
+                                size_t size);
+uint32_t ComputeBuiltinChecksumWithLastByte(ChecksumType type, const char* data,
+                                            size_t size, char last_byte);
 
 // Represents the contents of a block read from an SST file. Depending on how
 // it's created, it may or may not own the actual block bytes. As an example,
@@ -313,15 +312,6 @@ struct BlockContents {
   }
 };
 
-// Read the block identified by "handle" from "file".  On failure
-// return non-OK.  On success fill *result and return OK.
-extern Status ReadBlockContents(
-    RandomAccessFileReader* file, FilePrefetchBuffer* prefetch_buffer,
-    const Footer& footer, const ReadOptions& options, const BlockHandle& handle,
-    BlockContents* contents, const ImmutableOptions& ioptions,
-    bool do_uncompress = true, const Slice& compression_dict = Slice(),
-    const PersistentCacheOptions& cache_options = PersistentCacheOptions());
-
 // The 'data' points to the raw block contents read in from file.
 // This method allocates a new heap buffer and the raw block
 // contents are uncompresed into this buffer. This buffer is
@@ -352,8 +342,7 @@ extern Status ReifyDbHostIdProperty(Env* env, std::string* db_host_id);
 // TODO(andrewkr): we should prefer one way of representing a null/uninitialized
 // BlockHandle. Currently we use zeros for null and use negation-of-zeros for
 // uninitialized.
-inline BlockHandle::BlockHandle()
-    : BlockHandle(~static_cast<uint64_t>(0), ~static_cast<uint64_t>(0)) {}
+inline BlockHandle::BlockHandle() : BlockHandle(~uint64_t{0}, ~uint64_t{0}) {}
 
 inline BlockHandle::BlockHandle(uint64_t _offset, uint64_t _size)
     : offset_(_offset), size_(_size) {}

table/table_test.cc

@@ -2231,73 +2231,109 @@ TEST_P(BlockBasedTableTest, BadChecksumType) {
 }
 
 namespace {
-std::string TrailerAsString(const std::string& contents,
-                            CompressionType compression_type,
+std::string ChecksumAsString(const std::string& data,
                              ChecksumType checksum_type) {
-  std::array<char, kBlockTrailerSize> trailer;
-  BlockBasedTableBuilder::ComputeBlockTrailer(contents, compression_type,
-                                              checksum_type, &trailer);
-  return Slice(trailer.data(), trailer.size()).ToString(/*hex*/ true);
+  uint32_t v = ComputeBuiltinChecksum(checksum_type, data.data(), data.size());
+
+  // Verify consistency with other function
+  if (data.size() >= 1) {
+    EXPECT_EQ(v, ComputeBuiltinChecksumWithLastByte(
+                     checksum_type, data.data(), data.size() - 1, data.back()));
+  }
+  // Little endian as in file
+  std::array<char, 4> raw_bytes;
+  EncodeFixed32(raw_bytes.data(), v);
+  return Slice(raw_bytes.data(), raw_bytes.size()).ToString(/*hex*/ true);
+}
+
+std::string ChecksumAsString(std::string* data, char new_last_byte,
+                             ChecksumType checksum_type) {
+  data->back() = new_last_byte;
+  return ChecksumAsString(*data, checksum_type);
 }
 }  // namespace
 
 // Make sure that checksum values don't change in later versions, even if
-// consistent within current version. (Other tests check for consistency
-// between written checksums and read-time validation, so here we only
-// have to verify the writer side.)
+// consistent within current version.
 TEST_P(BlockBasedTableTest, ChecksumSchemas) {
-  std::string b1 = "This is a short block!";
+  std::string b0 = "x";
+  std::string b1 = "This is a short block!x";
   std::string b2;
   for (int i = 0; i < 100; ++i) {
     b2.append("This is a long block!");
   }
-  CompressionType ct1 = kNoCompression;
-  CompressionType ct2 = kSnappyCompression;
-  CompressionType ct3 = kZSTD;
+  b2.append("x");
+  // Trailing 'x' will be replaced by compression type
+
+  std::string empty;
+
+  char ct1 = kNoCompression;
+  char ct2 = kSnappyCompression;
+  char ct3 = kZSTD;
 
   // Note: first byte of trailer is compression type, last 4 are checksum
 
   for (ChecksumType t : GetSupportedChecksums()) {
     switch (t) {
       case kNoChecksum:
-        EXPECT_EQ(TrailerAsString(b1, ct1, t), "0000000000");
-        EXPECT_EQ(TrailerAsString(b1, ct2, t), "0100000000");
-        EXPECT_EQ(TrailerAsString(b1, ct3, t), "0700000000");
-        EXPECT_EQ(TrailerAsString(b2, ct1, t), "0000000000");
-        EXPECT_EQ(TrailerAsString(b2, ct2, t), "0100000000");
-        EXPECT_EQ(TrailerAsString(b2, ct3, t), "0700000000");
+        EXPECT_EQ(ChecksumAsString(empty, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b0, ct1, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b0, ct2, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b0, ct3, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b1, ct1, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b1, ct2, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b1, ct3, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b2, ct1, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b2, ct2, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b2, ct3, t), "00000000");
         break;
       case kCRC32c:
-        EXPECT_EQ(TrailerAsString(b1, ct1, t), "00583F0355");
-        EXPECT_EQ(TrailerAsString(b1, ct2, t), "012F9B0A57");
-        EXPECT_EQ(TrailerAsString(b1, ct3, t), "07ECE7DA1D");
-        EXPECT_EQ(TrailerAsString(b2, ct1, t), "00943EF0AB");
-        EXPECT_EQ(TrailerAsString(b2, ct2, t), "0143A2EDB1");
-        EXPECT_EQ(TrailerAsString(b2, ct3, t), "0700E53D63");
+        EXPECT_EQ(ChecksumAsString(empty, t), "D8EA82A2");
+        EXPECT_EQ(ChecksumAsString(&b0, ct1, t), "D28F2549");
+        EXPECT_EQ(ChecksumAsString(&b0, ct2, t), "052B2843");
+        EXPECT_EQ(ChecksumAsString(&b0, ct3, t), "46F8F711");
+        EXPECT_EQ(ChecksumAsString(&b1, ct1, t), "583F0355");
+        EXPECT_EQ(ChecksumAsString(&b1, ct2, t), "2F9B0A57");
+        EXPECT_EQ(ChecksumAsString(&b1, ct3, t), "ECE7DA1D");
+        EXPECT_EQ(ChecksumAsString(&b2, ct1, t), "943EF0AB");
+        EXPECT_EQ(ChecksumAsString(&b2, ct2, t), "43A2EDB1");
+        EXPECT_EQ(ChecksumAsString(&b2, ct3, t), "00E53D63");
         break;
       case kxxHash:
-        EXPECT_EQ(TrailerAsString(b1, ct1, t), "004A2E5FB0");
-        EXPECT_EQ(TrailerAsString(b1, ct2, t), "010BD9F652");
-        EXPECT_EQ(TrailerAsString(b1, ct3, t), "07B4107E50");
-        EXPECT_EQ(TrailerAsString(b2, ct1, t), "0020F4D4BA");
-        EXPECT_EQ(TrailerAsString(b2, ct2, t), "018F1A1F99");
-        EXPECT_EQ(TrailerAsString(b2, ct3, t), "07A191A338");
+        EXPECT_EQ(ChecksumAsString(empty, t), "055DCC02");
+        EXPECT_EQ(ChecksumAsString(&b0, ct1, t), "3EB065CF");
+        EXPECT_EQ(ChecksumAsString(&b0, ct2, t), "31F79238");
+        EXPECT_EQ(ChecksumAsString(&b0, ct3, t), "320D2E00");
+        EXPECT_EQ(ChecksumAsString(&b1, ct1, t), "4A2E5FB0");
+        EXPECT_EQ(ChecksumAsString(&b1, ct2, t), "0BD9F652");
+        EXPECT_EQ(ChecksumAsString(&b1, ct3, t), "B4107E50");
+        EXPECT_EQ(ChecksumAsString(&b2, ct1, t), "20F4D4BA");
+        EXPECT_EQ(ChecksumAsString(&b2, ct2, t), "8F1A1F99");
+        EXPECT_EQ(ChecksumAsString(&b2, ct3, t), "A191A338");
         break;
       case kxxHash64:
-        EXPECT_EQ(TrailerAsString(b1, ct1, t), "00B74655EF");
-        EXPECT_EQ(TrailerAsString(b1, ct2, t), "01B6C8BBBE");
-        EXPECT_EQ(TrailerAsString(b1, ct3, t), "07AED9E3B4");
-        EXPECT_EQ(TrailerAsString(b2, ct1, t), "000D4999FE");
-        EXPECT_EQ(TrailerAsString(b2, ct2, t), "01F5932423");
-        EXPECT_EQ(TrailerAsString(b2, ct3, t), "076B31BAB1");
+        EXPECT_EQ(ChecksumAsString(empty, t), "99E9D851");
+        EXPECT_EQ(ChecksumAsString(&b0, ct1, t), "682705DB");
+        EXPECT_EQ(ChecksumAsString(&b0, ct2, t), "30E7211B");
+        EXPECT_EQ(ChecksumAsString(&b0, ct3, t), "B7BB58E8");
+        EXPECT_EQ(ChecksumAsString(&b1, ct1, t), "B74655EF");
+        EXPECT_EQ(ChecksumAsString(&b1, ct2, t), "B6C8BBBE");
+        EXPECT_EQ(ChecksumAsString(&b1, ct3, t), "AED9E3B4");
+        EXPECT_EQ(ChecksumAsString(&b2, ct1, t), "0D4999FE");
+        EXPECT_EQ(ChecksumAsString(&b2, ct2, t), "F5932423");
+        EXPECT_EQ(ChecksumAsString(&b2, ct3, t), "6B31BAB1");
         break;
       case kXXH3:
-        EXPECT_EQ(TrailerAsString(b1, ct1, t), "00B37FB5E6");
-        EXPECT_EQ(TrailerAsString(b1, ct2, t), "016AFC258D");
-        EXPECT_EQ(TrailerAsString(b1, ct3, t), "075CE54616");
-        EXPECT_EQ(TrailerAsString(b2, ct1, t), "00FA2D482E");
-        EXPECT_EQ(TrailerAsString(b2, ct2, t), "0123AED845");
-        EXPECT_EQ(TrailerAsString(b2, ct3, t), "0715B7BBDE");
+        EXPECT_EQ(ChecksumAsString(empty, t), "00000000");
+        EXPECT_EQ(ChecksumAsString(&b0, ct1, t), "C294D338");
+        EXPECT_EQ(ChecksumAsString(&b0, ct2, t), "1B174353");
+        EXPECT_EQ(ChecksumAsString(&b0, ct3, t), "2D0E20C8");
+        EXPECT_EQ(ChecksumAsString(&b1, ct1, t), "B37FB5E6");
+        EXPECT_EQ(ChecksumAsString(&b1, ct2, t), "6AFC258D");
+        EXPECT_EQ(ChecksumAsString(&b1, ct3, t), "5CE54616");
+        EXPECT_EQ(ChecksumAsString(&b2, ct1, t), "FA2D482E");
+        EXPECT_EQ(ChecksumAsString(&b2, ct2, t), "23AED845");
+        EXPECT_EQ(ChecksumAsString(&b2, ct3, t), "15B7BBDE");
         break;
       default:
         // Force this test to be updated on new ChecksumTypes