Implement basic classes for HPACK (HTTP/2 compression)

net/spdy/hpack_encoding_context.h

+#ifndef NET_SPDY_HPACK_ENCODING_CONTEXT_H_
+#define NET_SPDY_HPACK_ENCODING_CONTEXT_H_
+
+#include <cstddef>
+#include <deque>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+#include "base/strings/string_piece.h"
+#include "net/spdy/hpack_header_table.h"
+
+// All section references below are to
+// http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-04
+// .
+
+namespace net {
+
+// An encoding context is simply a header table and its associated
+// reference set and a static table.
+class HpackEncodingContext {
+ public:
+  // The constant returned by GetTouchesAt() if the indexed entry
+  // hasn't been touched (which is distinct from having a touch count
+  // of 0).
+  //
+  // TODO(akalin): The distinction between untouched and having a
+  // touch count of 0 is confusing. Think of a better way to represent
+  // this state.
+  static const uint32 kUntouched;
+
+  HpackEncodingContext();
+
+  ~HpackEncodingContext();
+
+  uint32 GetEntryCount() const;
+
+  // For all accessor below, index must be < GetEntryCount().
+
+  // The StringPieces returned by Get{Name,Value}At() live as long as
+  // the next call to SetMaxSize() or the Process*() functions.
+
+  base::StringPiece GetNameAt(uint32 index) const;
+
+  base::StringPiece GetValueAt(uint32 index) const;
+
+  bool IsReferencedAt(uint32 index) const;
+
+  uint32 GetTouchCountAt(uint32 index) const;
+
+  void SetReferencedAt(uint32 index, bool referenced);
+
+  // Adds the given number of touches to the entry at the given
+  // index. It is guaranteed that GetTouchCountAt(index) will not
+  // equal kUntouched after this function is called (even if
+  // touch_count == 0).
+  void AddTouchesAt(uint32 index, uint32 touch_count);
+
+  // Sets the touch count of the entry at the given index to
+  // kUntouched.
+  void ClearTouchesAt(uint32 index);
+
+  // Sets the maximum size of the encoding text, evicting entries if
+  // necessary.
+  void SetMaxSize(uint32 max_size);
+
+  // The Process*() functions below return true on success and false
+  // if an error was encountered.
+
+  // Tries to update the encoding context given an indexed header
+  // opcode for the given index as described in 3.2.1. new_index is
+  // filled in with the index of a mutable entry, or -1 if one was not
+  // able to be created. removed_referenced_indices is filled in with
+  // the indices of all entries removed from the reference set.
+  bool ProcessIndexedHeader(uint32 index,
+                            int32* new_index,
+                            std::vector<uint32>* removed_referenced_indices);
+
+  // Tries to update the encoding context given a literal header with
+  // incremental indexing opcode for the given name and value as
+  // described in 3.2.1. index is filled in with the index of the new
+  // entry if the header was successfully indexed, or -1 if
+  // not. removed_referenced_indices is filled in with the indices of
+  // all entries removed from the reference set.
+  bool ProcessLiteralHeaderWithIncrementalIndexing(
+      base::StringPiece name,
+      base::StringPiece value,
+      int32* index,
+      std::vector<uint32>* removed_referenced_indices);
+
+ private:
+  HpackHeaderTable header_table_;
+
+  DISALLOW_COPY_AND_ASSIGN(HpackEncodingContext);
+};
+
+}  // namespace net
+
+#endif  // NET_SPDY_HPACK_ENCODING_CONTEXT_H_