Refactor WireEncoder.

Change-Id: I50106755ce5571821d6e36767b16d08b91f054de

src/nt_wireencoder.h

@@ -0,0 +1,106 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2015. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#ifndef NT_WIREENCODER_H_
+#define NT_WIREENCODER_H_
+
+#include <cassert>
+#include <cstddef>
+
+#include "ntcore.h"
+
+namespace NtImpl {
+
+class WireEncoder
+{
+public:
+    explicit WireEncoder(unsigned int proto_rev);
+    ~WireEncoder();
+
+    void SetProtocolRev(unsigned int proto_rev)
+    {
+        m_proto_rev = proto_rev;
+    }
+
+    void Reset()
+    {
+        m_cur = m_start;
+        m_error = 0;
+    }
+
+    const char *GetError() const
+    {
+        return m_error;
+    }
+
+    const char *GetData() const
+    {
+        return m_start;
+    }
+
+    std::size_t GetSize() const
+    {
+        return m_cur - m_start;
+    }
+
+    void Reserve(std::size_t len)
+    {
+        //assert(m_end > m_cur);
+        if (static_cast<size_t>(m_end - m_cur) < len)
+            ReserveSlow(len);
+    }
+
+    void Write8(unsigned int val)
+    {
+        Reserve(1);
+        *m_cur++ = (char)(val & 0xff);
+    }
+
+    void Write16(unsigned int val)
+    {
+        Reserve(2);
+        *m_cur++ = (char)((val >> 8) & 0xff);
+        *m_cur++ = (char)(val & 0xff);
+    }
+
+    void Write32(unsigned long val)
+    {
+        Reserve(4);
+        *m_cur++ = (char)((val >> 24) & 0xff);
+        *m_cur++ = (char)((val >> 16) & 0xff);
+        *m_cur++ = (char)((val >> 8) & 0xff);
+        *m_cur++ = (char)(val & 0xff);
+    }
+
+    void WriteDouble(double val);
+
+    void WriteULEB128(unsigned long val);
+    void WriteType(NT_Type type);
+    void WriteValue(const NT_Value &value);
+    void WriteString(const NT_String &str);
+
+    std::size_t GetValueSize(const NT_Value &value);
+    std::size_t GetStringSize(const NT_String &str);
+
+protected:
+    unsigned int m_proto_rev;
+    const char *m_error;
+
+private:
+    WireEncoder(const WireEncoder&);
+    WireEncoder& operator= (const WireEncoder&);
+
+    void ReserveSlow(std::size_t len);
+
+    char *m_start;
+    char *m_cur;
+    char *m_end;
+};
+
+} // namespace NtImpl
+
+#endif /* NT_WIREENCODER_H_ */