intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 79 insertions, 0 deletions

diff --git a/library/cpp/yson_pull/buffer.h b/library/cpp/yson_pull/buffer.h
new file mode 100644
index 0000000000..04c9220ef3
--- /dev/null
+++ b/library/cpp/yson_pull/buffer.h
@@ -0,0 +1,79 @@
+#pragma once
+
+#include <util/system/types.h>
+#include <util/system/yassert.h>
+
+#include <cstddef>
+
+namespace NYsonPull {
+    //! \brief A non-owning buffer model.
+    //!
+    //! Represents a \p pos pointer moving between \p begin and \p end.
+    template <typename T>
+    class buffer {
+        T* begin_ = nullptr;
+        T* pos_ = nullptr;
+        T* end_ = nullptr;
+
+    public:
+        T* begin() const noexcept {
+            return begin_;
+        }
+        T* pos() const noexcept {
+            return pos_;
+        }
+        T* end() const noexcept {
+            return end_;
+        }
+
+        //! \brief Amount of data after current position.
+        size_t available() const noexcept {
+            return end_ - pos_;
+        }
+
+        //! \brief Amount of data before current position.
+        size_t used() const noexcept {
+            return pos_ - begin_;
+        }
+
+        //! \brief Move current position \p nbytes forward.
+        void advance(size_t nbytes) noexcept {
+            Y_ASSERT(pos_ + nbytes <= end_);
+            pos_ += nbytes;
+        }
+
+        //! \brief Reset buffer pointers.
+        void reset(T* new_begin, T* new_end, T* new_pos) {
+            begin_ = new_begin;
+            pos_ = new_pos;
+            end_ = new_end;
+        }
+
+        //! \brief Reset buffer to beginning
+        void reset(T* new_begin, T* new_end) {
+            reset(new_begin, new_end, new_begin);
+        }
+    };
+
+    class output_buffer: public buffer<ui8> {
+    public:
+        //! \brief An output buffer is empty when there is no data written to it.
+        bool is_empty() const noexcept {
+            return pos() == begin();
+        }
+
+        //! \brief An output buffer is full when there is no space to write more data to it.
+        bool is_full() const noexcept {
+            return pos() == end();
+        }
+    };
+
+    class input_buffer: public buffer<const ui8> {
+    public:
+        //! An input stream is empty when there is no data to read in it.
+        bool is_empty() const noexcept {
+            return pos() == end();
+        }
+    };
+
+}