diff --git a/rdr/InStream.h b/rdr/InStream.h
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+++ b/rdr/InStream.h
@@ -0,0 +1,153 @@
+/* Copyright (C) 2002-2003 RealVNC Ltd.  All Rights Reserved.
+ *    
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+//
+// rdr::InStream marshalls data from a buffer stored in RDR (RFB Data
+// Representation).
+//
+
+#ifndef __RDR_INSTREAM_H__
+#define __RDR_INSTREAM_H__
+
+#include <rdr/types.h>
+#include <string.h> // for memcpy
+
+namespace rdr {
+
+  class InStream {
+
+  public:
+
+    virtual ~InStream() {}
+
+    // check() ensures there is buffer data for at least one item of size
+    // itemSize bytes.  Returns the number of items in the buffer (up to a
+    // maximum of nItems).  If wait is false, then instead of blocking to wait
+    // for the bytes, zero is returned if the bytes are not immediately
+    // available.
+
+    inline int check(int itemSize, int nItems=1, bool wait=true)
+    {
+      if (ptr + itemSize * nItems > end) {
+        if (ptr + itemSize > end)
+          return overrun(itemSize, nItems, wait);
+
+        nItems = (end - ptr) / itemSize;
+      }
+      return nItems;
+    }
+
+    // checkNoWait() tries to make sure that the given number of bytes can
+    // be read without blocking.  It returns true if this is the case, false
+    // otherwise.  The length must be "small" (less than the buffer size).
+
+    inline bool checkNoWait(int length) { return check(length, 1, false)!=0; }
+
+    // readU/SN() methods read unsigned and signed N-bit integers.
+
+    inline U8  readU8()  { check(1); return *ptr++; }
+    inline U16 readU16() { check(2); int b0 = *ptr++; int b1 = *ptr++;
+                           return b0 << 8 | b1; }
+    inline U32 readU32() { check(4); int b0 = *ptr++; int b1 = *ptr++;
+                                     int b2 = *ptr++; int b3 = *ptr++;
+                           return b0 << 24 | b1 << 16 | b2 << 8 | b3; }
+
+    inline S8  readS8()  { return (S8) readU8();  }
+    inline S16 readS16() { return (S16)readU16(); }
+    inline S32 readS32() { return (S32)readU32(); }
+
+    // readString() reads a string - a U32 length followed by the data.
+    // Returns a null-terminated string - the caller should delete[] it
+    // afterwards.
+
+    char* readString();
+
+    // maxStringLength protects against allocating a huge buffer.  Set it
+    // higher if you need longer strings.
+
+    static U32 maxStringLength;
+
+    inline void skip(int bytes) {
+      while (bytes > 0) {
+        int n = check(1, bytes);
+        ptr += n;
+        bytes -= n;
+      }
+    }
+
+    // readBytes() reads an exact number of bytes.
+
+    virtual void readBytes(void* data, int length) {
+      U8* dataPtr = (U8*)data;
+      U8* dataEnd = dataPtr + length;
+      while (dataPtr < dataEnd) {
+        int n = check(1, dataEnd - dataPtr);
+        memcpy(dataPtr, ptr, n);
+        ptr += n;
+        dataPtr += n;
+      }
+    }
+
+    // readOpaqueN() reads a quantity without byte-swapping.
+
+    inline U8  readOpaque8()  { return readU8(); }
+    inline U16 readOpaque16() { check(2); U16 r; ((U8*)&r)[0] = *ptr++;
+                                ((U8*)&r)[1] = *ptr++; return r; }
+    inline U32 readOpaque32() { check(4); U32 r; ((U8*)&r)[0] = *ptr++;
+                                ((U8*)&r)[1] = *ptr++; ((U8*)&r)[2] = *ptr++;
+                                ((U8*)&r)[3] = *ptr++; return r; }
+    inline U32 readOpaque24A() { check(3); U32 r=0; ((U8*)&r)[0] = *ptr++;
+                                 ((U8*)&r)[1] = *ptr++; ((U8*)&r)[2] = *ptr++;
+                                 return r; }
+    inline U32 readOpaque24B() { check(3); U32 r=0; ((U8*)&r)[1] = *ptr++;
+                                 ((U8*)&r)[2] = *ptr++; ((U8*)&r)[3] = *ptr++;
+                                 return r; }
+
+    // pos() returns the position in the stream.
+
+    virtual int pos() = 0;
+
+    // getptr(), getend() and setptr() are "dirty" methods which allow you to
+    // manipulate the buffer directly.  This is useful for a stream which is a
+    // wrapper around an underlying stream.
+
+    inline const U8* getptr() const { return ptr; }
+    inline const U8* getend() const { return end; }
+    inline void setptr(const U8* p) { ptr = p; }
+
+  private:
+
+    // overrun() is implemented by a derived class to cope with buffer overrun.
+    // It ensures there are at least itemSize bytes of buffer data.  Returns
+    // the number of items in the buffer (up to a maximum of nItems).  itemSize
+    // is supposed to be "small" (a few bytes).  If wait is false, then
+    // instead of blocking to wait for the bytes, zero is returned if the bytes
+    // are not immediately available.
+
+    virtual int overrun(int itemSize, int nItems, bool wait=true) = 0;
+
+  protected:
+
+    InStream() {}
+    const U8* ptr;
+    const U8* end;
+  };
+
+}
+
+#endif