Refactor MessageReader into WireDecoder.

Change-Id: If5842b4f6b9a7db3d3de515cd71324ab7ee82f50

src/nt_wiredecoder.h

@@ -0,0 +1,108 @@
+/*----------------------------------------------------------------------------*/
+/* 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_WIREDECODER_H_
+#define NT_WIREDECODER_H_
+
+#include <cstddef>
+
+#include "ntcore.h"
+#include "nt_leb128.h"
+#include "nt_raw_istream.h"
+#include "nt_encoding.h"
+
+namespace NtImpl {
+
+class WireDecoder
+{
+public:
+    explicit WireDecoder(raw_istream& is, unsigned int proto_rev);
+    ~WireDecoder();
+
+    void SetProtocolRev(unsigned int proto_rev)
+    {
+        m_proto_rev = proto_rev;
+    }
+
+    void Reset()
+    {
+        m_error = 0;
+    }
+
+    const char *GetError() const
+    {
+        return m_error;
+    }
+
+    bool Read(char **buf, std::size_t len)
+    {
+        if (len > m_allocated)
+            Realloc(len);
+        *buf = m_buf;
+        return m_is.read(m_buf, len);
+    }
+
+    bool Read8(unsigned int *val)
+    {
+        char *buf;
+        if (!Read(&buf, 1)) return false;
+        *val = NtImpl::Read8(buf);
+        return true;
+    }
+
+    bool Read16(unsigned int *val)
+    {
+        char *buf;
+        if (!Read(&buf, 2)) return false;
+        *val = NtImpl::Read16(buf);
+        return true;
+    }
+
+    bool Read32(unsigned long *val)
+    {
+        char *buf;
+        if (!Read(&buf, 4)) return false;
+        *val = NtImpl::Read32(buf);
+        return true;
+    }
+
+    bool ReadDouble(double *val)
+    {
+        char *buf;
+        if (!Read(&buf, 8)) return false;
+        *val = NtImpl::ReadDouble(buf);
+        return true;
+    }
+
+    bool ReadULEB128(unsigned long *val)
+    {
+        return read_uleb128(m_is, val);
+    }
+
+    bool ReadType(NT_Type *type);
+    bool ReadValue(NT_Type type, NT_Value *value);
+    bool ReadString(NT_String *str);
+
+protected:
+    unsigned int m_proto_rev;
+    const char *m_error;
+
+private:
+    WireDecoder(const WireDecoder&);
+    WireDecoder& operator= (const WireDecoder&);
+
+    void Realloc(std::size_t len);
+
+    raw_istream &m_is;
+
+    char *m_buf;
+    std::size_t m_allocated;
+};
+
+} // namespace NtImpl
+
+#endif /* NT_WIREDECODER_H_ */