HPACK: Implement delta encoding.

net/spdy/hpack_encoder.h

Index: net/spdy/hpack_encoder.h
diff --git a/net/spdy/hpack_encoder.h b/net/spdy/hpack_encoder.h
index 5a6b8ca8a1969c49ab052fd2fec6f655f377b845..df504f50f83e52c39e1a53ae2fe074a10cc02f5b 100644
--- a/net/spdy/hpack_encoder.h
+++ b/net/spdy/hpack_encoder.h
@@ -7,11 +7,13 @@
 
 #include <map>
 #include <string>
+#include <vector>
 
 #include "base/basictypes.h"
 #include "base/macros.h"
 #include "base/strings/string_piece.h"
 #include "net/base/net_export.h"
+#include "net/spdy/hpack_header_table.h"
 #include "net/spdy/hpack_output_stream.h"
 
 // An HpackEncoder encodes header sets as outlined in
@@ -19,6 +21,8 @@
 
 namespace net {
 
+class HpackHuffmanTable;
+
 namespace test {
 class HpackEncoderPeer;
 }  // namespace test
@@ -27,7 +31,9 @@ class NET_EXPORT_PRIVATE HpackEncoder {
  public:
   friend class test::HpackEncoderPeer;
 
-  explicit HpackEncoder();
+  // |table| is an initialized HPACK Huffman table, having an
+  // externally-managed lifetime which spans beyond HpackEncoder.
+  explicit HpackEncoder(const HpackHuffmanTable& table);
   ~HpackEncoder();
 
   // Encodes the given header set into the given string. Returns
@@ -35,15 +41,52 @@ class NET_EXPORT_PRIVATE HpackEncoder {
   bool EncodeHeaderSet(const std::map<std::string, std::string>& header_set,
                        std::string* output);
 
+  // Encodes the given header set into the given string. Only non-indexed
+  // literal representations are emitted, bypassing the header table. Huffman
+  // coding is also not used. Returns whether the encoding was successful.
+  // TODO(jgraettinger): Enable Huffman coding once the table as stablized.
+  bool EncodeHeaderSetWithoutCompression(
+      const std::map<std::string, std::string>& header_set,
+      std::string* output);
+
+  // Called upon a change to SETTINGS_HEADER_TABLE_SIZE. Specifically, this
+  // is to be called after receiving (and sending an acknowledgement for) a
+  // SETTINGS_HEADER_TABLE_SIZE update from the remote decoding endpoint.
+  void ApplyHeaderTableSizeSetting(size_t size_setting) {
+    header_table_.SetSettingsHeaderTableSize(size_setting);
+  }
+
  private:
-  void EmitNonIndexedLiteral(base::StringPiece name,
-                             base::StringPiece value,
-                             HpackOutputStream* output_stream);
+  typedef std::pair<base::StringPiece, base::StringPiece> Representation;
+  typedef std::vector<Representation> Representations;
+
+  // Emits a static/dynamic indexed representation (Section 4.2).
+  void EmitDynamicIndex(HpackEntry* entry);
+  void EmitStaticIndex(HpackEntry* entry);
+
+  // Emits a literal representation (Section 4.3).
+  void EmitIndexedLiteral(const Representation& representation);
+  void EmitNonIndexedLiteral(const Representation& representation);
+  void EmitLiteral(const Representation& representation);
+
+  // Emits a Huffman or identity string (whichever is smaller).
+  void EmitString(base::StringPiece str);
+
+  // Determines the representation delta required to encode |header_set| in
+  // the current header table context. Entries in the reference set are
+  // enumerated and marked with membership in the current |header_set|.
+  // Representations which must be explicitly emitted are returned.
+  Representations DetermineEncodingDelta(
+      const std::map<std::string, std::string>& header_set);
+
+  static void CookieToCrumbs(const Representation& cookie,
+                             Representations* crumbs_out);
 
-  static void CookieToCrumbs(base::StringPiece cookie,
-                             std::vector<base::StringPiece>* out);
+  HpackHeaderTable header_table_;
+  HpackOutputStream output_stream_;
 
-  uint32 max_string_literal_size_;
+  bool allow_huffman_compression_;
+  const HpackHuffmanTable& huffman_table_;
 
   DISALLOW_COPY_AND_ASSIGN(HpackEncoder);
 };