Implement PacketReader handling just one buffer

src/network/PacketReader.h

@@ -0,0 +1,52 @@
+#pragma once
+
+#include <cstdio>
+#include <cstdint>
+
+namespace Feather::Network
+{
+
+    // Class to read packet data, such as is produced by NetworkMessage
+    class PacketReader
+    {
+    public:
+        PacketReader(const uint8_t *const dataPtr) :
+            m_data(dataPtr),
+            m_length(ReadVarInt())
+        {}
+
+        inline uint8_t ReadByte()
+        {
+            return m_data[m_offset++];
+        }
+
+        int ReadVarInt()
+        {
+            int numRead = 0;
+            int result = 0;
+            uint8_t read;
+            do
+            {
+                read = ReadByte();
+                int value = (read & 0b01111111);
+                result |= (value << (7 * numRead));
+
+                numRead++;
+                if (numRead > 5)
+                {
+                    // complain
+                    //throw new RuntimeException("VarInt is too big");
+                }
+            } while ((read & 0b10000000) != 0);
+
+            return result;
+        }
+
+        uint32_t Length() const { return m_length; }
+    private:
+        const uint32_t          m_length;
+        const uint8_t *const    m_data;
+        uint32_t                m_offset = 0;
+    };
+
+}