Repo created

libs/coding/reader_writer_ops.cpp

@@ -0,0 +1,32 @@
+#include "coding/reader_writer_ops.hpp"
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+namespace rw_ops
+{
+void Reverse(Reader const & src, Writer & dest)
+{
+  // Read from end, reverse and write directly.
+
+  size_t const bufSz = 1024;
+  std::vector<uint8_t> buffer(bufSz);
+
+  uint64_t pos = src.Size();
+  while (pos > 0)
+  {
+    size_t const sz = pos > bufSz ? bufSz : static_cast<size_t>(pos);
+    ASSERT_GREATER_OR_EQUAL(pos, sz, ());
+
+    src.Read(pos - sz, &buffer[0], sz);
+
+    std::reverse(buffer.begin(), buffer.begin() + sz);
+
+    dest.Write(&buffer[0], sz);
+
+    pos -= sz;
+  }
+}
+}  // namespace rw_ops