intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 81 insertions, 0 deletions

diff --git a/library/cpp/yson_pull/input.h b/library/cpp/yson_pull/input.h
new file mode 100644
index 0000000000..2cdfae857e
--- /dev/null
+++ b/library/cpp/yson_pull/input.h
@@ -0,0 +1,81 @@
+#pragma once
+
+#include "buffer.h"
+
+#include <util/generic/ptr.h>
+#include <util/generic/strbuf.h>
+#include <util/system/types.h>
+#include <util/system/yassert.h>
+
+#include <cstddef>
+#include <memory>
+
+class IInputStream;
+class IZeroCopyInput;
+
+namespace NYsonPull {
+    namespace NInput {
+        //! \brief Input stream adaptor interface.
+        //!
+        //! Represents a model of a chunked input data stream.
+        class IStream {
+            input_buffer buffer_;
+            bool at_end_ = false;
+
+        public:
+            virtual ~IStream() = default;
+
+            bool at_end() const {
+                return at_end_;
+            }
+
+            input_buffer& buffer() noexcept {
+                return buffer_;
+            }
+            const input_buffer& buffer() const noexcept {
+                return buffer_;
+            }
+
+            void fill_buffer() {
+                while (buffer_.is_empty() && !at_end()) {
+                    at_end_ = do_fill_buffer() == result::at_end;
+                }
+            }
+
+        protected:
+            enum class result {
+                have_more_data, //! May continue reading
+                at_end,         //! Reached end of stream
+            };
+
+            //! \brief Read next chunk of data.
+            //!
+            //! The implementation is to discard the buffer contents
+            //! and reset the buffer to a next chunk of data.
+            //! End-of-stream condition is to be reported via return value.
+            //!
+            //! Read is assumed to always succeed unless it throws an exception.
+            virtual result do_fill_buffer() = 0;
+        };
+
+        //! \brief Read data from a contiguous memory block (i.e. a string)
+        //!
+        //! Does not take ownership on memory.
+        THolder<IStream> FromMemory(TStringBuf data);
+
+        //! \brief Read data from C FILE* object.
+        //!
+        //! Does not take ownership on file object.
+        //! Data is buffered internally regardless of file buffering.
+        THolder<IStream> FromStdioFile(FILE* file, size_t buffer_size = 65536);
+
+        //! \brief Read data from POSIX file descriptor.
+        //!
+        //! Does not take ownership on streambuf.
+        THolder<IStream> FromPosixFd(int fd, size_t buffer_size = 65536);
+
+        THolder<IStream> FromZeroCopyInput(IZeroCopyInput* input);
+
+        THolder<IStream> FromInputStream(IInputStream* input, size_t buffer_size = 65536);
+    }
+}