Add TProtocolTap: a meta-protocol for "wiretapping".

TProtocolTap is a protocol that passes reads through to a "source" protocol,
but mirrors them as writes to a "sink" protocol.


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665643 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/src/protocol/TProtocolTap.h b/lib/cpp/src/protocol/TProtocolTap.h
new file mode 100644
index 0000000..1259598
--- /dev/null
+++ b/lib/cpp/src/protocol/TProtocolTap.h
@@ -0,0 +1,175 @@
+// 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_TPROTOCOLTAP_H_
+#define _THRIFT_PROTOCOL_TPROTOCOLTAP_H_ 1
+
+#include <protocol/TOneWayProtocol.h>
+
+namespace facebook { namespace thrift { namespace protocol {
+
+using facebook::thrift::transport::TTransport;
+
+/**
+ * Puts a wiretap on a protocol object.  Any reads to this class are passed
+ * through to an enclosed protocol object, but also mirrored as write to a
+ * second protocol object.
+ *
+ * @author David Reiss <dreiss@facebook.com>
+ */
+class TProtocolTap : public TReadOnlyProtocol {
+ public:
+   TProtocolTap(boost::shared_ptr<TProtocol> source,
+                boost::shared_ptr<TProtocol> sink)
+     : TReadOnlyProtocol(source->getTransport(), "TProtocolTap")
+     , source_(source)
+     , sink_(sink)
+  {}
+
+  virtual uint32_t readMessageBegin(std::string& name,
+                                    TMessageType& messageType,
+                                    int32_t& seqid) {
+    uint32_t rv = source_->readMessageBegin(name, messageType, seqid);
+    sink_->writeMessageBegin(name, messageType, seqid);
+    return rv;
+  }
+
+  virtual uint32_t readMessageEnd() {
+    uint32_t rv = source_->readMessageEnd();
+    sink_->writeMessageEnd();
+    return rv;
+  }
+
+  virtual uint32_t readStructBegin(std::string& name) {
+    uint32_t rv = source_->readStructBegin(name);
+    sink_->writeStructBegin(name);
+    return rv;
+  }
+
+  virtual uint32_t readStructEnd() {
+    uint32_t rv = source_->readStructEnd();
+    sink_->writeStructEnd();
+    return rv;
+  }
+
+  virtual uint32_t readFieldBegin(std::string& name,
+                                  TType& fieldType,
+                                  int16_t& fieldId) {
+    uint32_t rv = source_->readFieldBegin(name, fieldType, fieldId);
+    if (fieldType == T_STOP) {
+      sink_->writeFieldStop();
+    } else {
+      sink_->writeFieldBegin(name, fieldType, fieldId);
+    }
+    return rv;
+  }
+
+
+  virtual uint32_t readFieldEnd() {
+    uint32_t rv = source_->readFieldEnd();
+    sink_->writeFieldEnd();
+    return rv;
+  }
+
+  virtual uint32_t readMapBegin(TType& keyType,
+                                TType& valType,
+                                uint32_t& size) {
+    uint32_t rv = source_->readMapBegin(keyType, valType, size);
+    sink_->writeMapBegin(keyType, valType, size);
+    return rv;
+  }
+
+
+  virtual uint32_t readMapEnd() {
+    uint32_t rv = source_->readMapEnd();
+    sink_->writeMapEnd();
+    return rv;
+  }
+
+  virtual uint32_t readListBegin(TType& elemType,
+                                 uint32_t& size) {
+    uint32_t rv = source_->readListBegin(elemType, size);
+    sink_->writeListBegin(elemType, size);
+    return rv;
+  }
+
+
+  virtual uint32_t readListEnd() {
+    uint32_t rv = source_->readListEnd();
+    sink_->writeListEnd();
+    return rv;
+  }
+
+  virtual uint32_t readSetBegin(TType& elemType,
+                                uint32_t& size) {
+    uint32_t rv = source_->readSetBegin(elemType, size);
+    sink_->writeSetBegin(elemType, size);
+    return rv;
+  }
+
+
+  virtual uint32_t readSetEnd() {
+    uint32_t rv = source_->readSetEnd();
+    sink_->writeSetEnd();
+    return rv;
+  }
+
+  virtual uint32_t readBool(bool& value) {
+    uint32_t rv = source_->readBool(value);
+    sink_->writeBool(value);
+    return rv;
+  }
+
+  virtual uint32_t readByte(int8_t& byte) {
+    uint32_t rv = source_->readByte(byte);
+    sink_->writeByte(byte);
+    return rv;
+  }
+
+  virtual uint32_t readI16(int16_t& i16) {
+    uint32_t rv = source_->readI16(i16);
+    sink_->writeI16(i16);
+    return rv;
+  }
+
+  virtual uint32_t readI32(int32_t& i32) {
+    uint32_t rv = source_->readI32(i32);
+    sink_->writeI32(i32);
+    return rv;
+  }
+
+  virtual uint32_t readI64(int64_t& i64) {
+    uint32_t rv = source_->readI64(i64);
+    sink_->writeI64(i64);
+    return rv;
+  }
+
+  virtual uint32_t readDouble(double& dub) {
+    uint32_t rv = source_->readDouble(dub);
+    sink_->writeDouble(dub);
+    return rv;
+  }
+
+  virtual uint32_t readString(std::string& str) {
+    uint32_t rv = source_->readString(str);
+    sink_->writeString(str);
+    return rv;
+  }
+
+  virtual uint32_t readBinary(std::string& str) {
+    uint32_t rv = source_->readBinary(str);
+    sink_->writeBinary(str);
+    return rv;
+  }
+
+ private:
+  boost::shared_ptr<TProtocol> source_;
+  boost::shared_ptr<TProtocol> sink_;
+};
+
+}}} // facebook::thrift::protocol
+
+#endif // #define _THRIFT_PROTOCOL_TPROTOCOLTAP_H_ 1