Thrift: TDenseProtocol.

Summary:
- Made some stuff in TBinaryProtocol protected instead of private.
- Added a preliminary version of TDenseProtocol.  This is still
  super highly experimental and gross, and I wrote a super scary
  comment to explain that to anyone foolish enough to try to use
  this in its current state.

Reviewed By: mcslee

Test Plan: test/DenseProtoTest.cpp

Revert Plan: ok

Memcache Impact:
Save memory if/when people use it.


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665247 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/src/protocol/TDenseProtocol.h b/lib/cpp/src/protocol/TDenseProtocol.h
new file mode 100644
index 0000000..ffc6afa
--- /dev/null
+++ b/lib/cpp/src/protocol/TDenseProtocol.h
@@ -0,0 +1,247 @@
+// Copyright (c) 2006- Facebook
+// Distributed under the Thrift Software License
+//
+// See accompanying file LICENSE or visit the Thrift site at:
+// http://developers.facebook.com/thrift/
+
+#ifndef _THRIFT_PROTOCOL_TDENSEPROTOCOL_H_
+#define _THRIFT_PROTOCOL_TDENSEPROTOCOL_H_ 1
+
+#include "TBinaryProtocol.h"
+
+namespace facebook { namespace thrift { namespace protocol {
+
+/**
+ * The dense protocol is designed to use as little space as possible.
+ *
+ * !!!WARNING!!!
+ * This class is still highly experimental.  Incompatible changes
+ * WILL be made to it without notice.  DO NOT USE IT YET unless
+ * you are coordinating your testing with the author.
+ *
+ * TODO(dreiss): New class write with old meta.
+ *
+ * We override all of TBinaryProtocol's methods.
+ * We inherit so that we can can explicitly call TBPs's primitive-writing
+ * methods within our versions.
+ *
+ * @author David Reiss <dreiss@facebook.com>
+ */
+class TDenseProtocol : public TBinaryProtocol {
+ protected:
+  static const int32_t VERSION_MASK = 0xffff0000;
+  // VERSION_2 (0x80010000)  is taken by TBinaryProtocol.
+  static const int32_t VERSION_2 = 0x80020000;
+
+ public:
+  typedef facebook::thrift::reflection::local::TypeSpec TypeSpec;
+
+  TDenseProtocol(boost::shared_ptr<TTransport> trans,
+                 TypeSpec* type_spec = NULL) :
+    TBinaryProtocol(trans),
+    type_spec_(type_spec) {
+      vli_save_16 = 0;
+      vli_save_32 = 0;
+      vli_save_64 = 0;
+      vli_save_sub = 0;
+      negs = 0;
+    }
+
+  TDenseProtocol(boost::shared_ptr<TTransport> trans,
+                  TypeSpec* type_spec,
+                  int32_t string_limit,
+                  int32_t container_limit) :
+    TBinaryProtocol(trans,
+                    string_limit,
+                    container_limit,
+                    true,
+                    true),
+    type_spec_(type_spec) {
+      vli_save_16 = 0;
+      vli_save_32 = 0;
+      vli_save_64 = 0;
+      vli_save_sub = 0;
+      negs = 0;
+    }
+
+  void setTypeSpec(TypeSpec* type_spec) {
+    type_spec_ = type_spec;
+  }
+  TypeSpec* getTypeSpec() {
+    return type_spec_;
+  }
+
+
+  /*
+   * Writing functions.
+   */
+
+  virtual uint32_t writeMessageBegin(const std::string& name,
+                                     const TMessageType messageType,
+                                     const int32_t seqid);
+
+  virtual uint32_t writeMessageEnd();
+
+
+  virtual uint32_t writeStructBegin(const std::string& name);
+
+  virtual uint32_t writeStructEnd();
+
+  virtual uint32_t writeFieldBegin(const std::string& name,
+                                   const TType fieldType,
+                                   const int16_t fieldId);
+
+  virtual uint32_t writeFieldEnd();
+
+  virtual uint32_t writeFieldStop();
+
+  virtual uint32_t writeMapBegin(const TType keyType,
+                                 const TType valType,
+                                 const uint32_t size);
+
+  virtual uint32_t writeMapEnd();
+
+  virtual uint32_t writeListBegin(const TType elemType,
+                                  const uint32_t size);
+
+  virtual uint32_t writeListEnd();
+
+  virtual uint32_t writeSetBegin(const TType elemType,
+                                 const uint32_t size);
+
+  virtual uint32_t writeSetEnd();
+
+  virtual uint32_t writeBool(const bool value);
+
+  virtual uint32_t writeByte(const int8_t byte);
+
+  virtual uint32_t writeI16(const int16_t i16);
+
+  virtual uint32_t writeI32(const int32_t i32);
+
+  virtual uint32_t writeI64(const int64_t i64);
+
+  virtual uint32_t writeDouble(const double dub);
+
+  virtual uint32_t writeString(const std::string& str);
+
+
+  /*
+   * Helper writing functions (don't do state transitions).
+   */
+  inline uint32_t subWriteI32(const int32_t i32);
+
+  uint32_t subWriteBool(const bool value) {
+    return TBinaryProtocol::writeBool(value);
+  }
+
+#if 0
+  // Use this version when subWriteI32 is moved in here.
+  uint32_t subWriteString(const std::string& str) {
+    uint32_t size = str.size();
+    uint32_t xfer = subWriteI32((int32_t)size);
+    if (size > 0) {
+      trans_->write((uint8_t*)str.data(), size);
+    }
+    return xfer + size;
+  }
+#else
+  inline uint32_t subWriteString(const std::string& str);
+#endif
+
+
+  /*
+   * Reading functions
+   */
+
+  uint32_t readMessageBegin(std::string& name,
+                            TMessageType& messageType,
+                            int32_t& seqid);
+
+  uint32_t readMessageEnd();
+
+  uint32_t readStructBegin(std::string& name);
+
+  uint32_t readStructEnd();
+
+  uint32_t readFieldBegin(std::string& name,
+                          TType& fieldType,
+                          int16_t& fieldId);
+
+  uint32_t readFieldEnd();
+
+  uint32_t readMapBegin(TType& keyType,
+                        TType& valType,
+                        uint32_t& size);
+
+  uint32_t readMapEnd();
+
+  uint32_t readListBegin(TType& elemType,
+                         uint32_t& size);
+
+  uint32_t readListEnd();
+
+  uint32_t readSetBegin(TType& elemType,
+                        uint32_t& size);
+
+  uint32_t readSetEnd();
+
+  uint32_t readBool(bool& value);
+
+  uint32_t readByte(int8_t& byte);
+
+  uint32_t readI16(int16_t& i16);
+
+  uint32_t readI32(int32_t& i32);
+
+  uint32_t readI64(int64_t& i64);
+
+  uint32_t readDouble(double& dub);
+
+  uint32_t readString(std::string& str);
+
+
+  /*
+   * Helper reading functions (don't do state transitions).
+   */
+  uint32_t subReadI32(int32_t& i32) {
+    return TBinaryProtocol::readI32(i32);
+  }
+
+  uint32_t subReadBool(bool& value) {
+    return TBinaryProtocol::readBool(value);
+  }
+
+  uint32_t subReadString(std::string& str) {
+    uint32_t xfer;
+    int32_t size;
+    xfer = subReadI32(size);
+    return xfer + readStringBody(str, size);
+  }
+
+
+
+ private:
+
+  inline void checkTType(const TType ttype);
+  inline void stateTransition();
+
+  TypeSpec* type_spec_;
+
+  std::vector<TypeSpec*> ts_stack_;   // TypeSpec stack.
+  std::vector<int>       idx_stack_;  // InDeX stack.
+  std::vector<bool>      mkv_stack_;  // Map Key/Vlue stack.
+                                      // True = key, False = value.
+
+  // XXX Remove these when wire format is finalized.
+ public:
+  int vli_save_16;
+  int vli_save_32;
+  int vli_save_64;
+  int vli_save_sub;
+  int negs;
+};
+
+}}} // facebook::thrift::protocol
+
+#endif // #ifndef _THRIFT_PROTOCOL_TDENSEPROTOCOL_H_