1 files changed, 83 insertions, 0 deletions
diff --git a/src/rocksdb/db/blob/blob_log_sequential_reader.h b/src/rocksdb/db/blob/blob_log_sequential_reader.h
new file mode 100644
index 000000000..98afa8518
--- /dev/null
+++ b/src/rocksdb/db/blob/blob_log_sequential_reader.h
@@ -0,0 +1,83 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#pragma once
+
+#include <memory>
+
+#include "db/blob/blob_log_format.h"
+#include "rocksdb/slice.h"
+
+#define MAX_HEADER_SIZE(a, b, c) (a > b ? (a > c ? a : c) : (b > c ? b : c))
+
+namespace ROCKSDB_NAMESPACE {
+
+class RandomAccessFileReader;
+class Env;
+class Statistics;
+class Status;
+class SystemClock;
+
+/**
+ * BlobLogSequentialReader is a general purpose log stream reader
+ * implementation. The actual job of reading from the device is implemented by
+ * the RandomAccessFileReader interface.
+ *
+ * Please see BlobLogWriter for details on the file and record layout.
+ */
+
+class BlobLogSequentialReader {
+ public:
+  enum ReadLevel {
+    kReadHeader,
+    kReadHeaderKey,
+    kReadHeaderKeyBlob,
+  };
+
+  // Create a reader that will return log records from "*file_reader".
+  BlobLogSequentialReader(std::unique_ptr<RandomAccessFileReader>&& file_reader,
+                          SystemClock* clock, Statistics* statistics);
+
+  // No copying allowed
+  BlobLogSequentialReader(const BlobLogSequentialReader&) = delete;
+  BlobLogSequentialReader& operator=(const BlobLogSequentialReader&) = delete;
+
+  ~BlobLogSequentialReader();
+
+  Status ReadHeader(BlobLogHeader* header);
+
+  // Read the next record into *record.  Returns true if read
+  // successfully, false if we hit end of the input. The contents filled in
+  // *record will only be valid until the next mutating operation on this
+  // reader.
+  // If blob_offset is non-null, return offset of the blob through it.
+  Status ReadRecord(BlobLogRecord* record, ReadLevel level = kReadHeader,
+                    uint64_t* blob_offset = nullptr);
+
+  Status ReadFooter(BlobLogFooter* footer);
+
+  void ResetNextByte() { next_byte_ = 0; }
+
+  uint64_t GetNextByte() const { return next_byte_; }
+
+ private:
+  Status ReadSlice(uint64_t size, Slice* slice, char* buf);
+
+  const std::unique_ptr<RandomAccessFileReader> file_;
+  SystemClock* clock_;
+
+  Statistics* statistics_;
+
+  Slice buffer_;
+  char header_buf_[MAX_HEADER_SIZE(BlobLogHeader::kSize, BlobLogFooter::kSize,
+                                   BlobLogRecord::kHeaderSize)];
+
+  // which byte to read next
+  uint64_t next_byte_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
+
+#undef MAX_HEADER_SIZE
+\ No newline at end of file