1 files changed, 69 insertions, 0 deletions
diff --git a/nxcomp/BlockCache.cpp b/nxcomp/BlockCache.cpp
new file mode 100644
index 000000000..f885290f0
--- /dev/null
+++ b/nxcomp/BlockCache.cpp
@@ -0,0 +1,69 @@
+/**************************************************************************/
+/*                                                                        */
+/* Copyright (c) 2001, 2010 NoMachine, http://www.nomachine.com/.         */
+/*                                                                        */
+/* NXCOMP, NX protocol compression and NX extensions to this software     */
+/* are copyright of NoMachine. Redistribution and use of the present      */
+/* software is allowed according to terms specified in the file LICENSE   */
+/* which comes in the source distribution.                                */
+/*                                                                        */
+/* Check http://www.nomachine.com/licensing.html for applicability.       */
+/*                                                                        */
+/* NX and NoMachine are trademarks of Medialogic S.p.A.                   */
+/*                                                                        */
+/* All rights reserved.                                                   */
+/*                                                                        */
+/**************************************************************************/
+
+#include <string.h>
+#include "BlockCache.h"
+
+
+int BlockCache::compare(unsigned int size, const unsigned char *data,
+                            int overwrite)
+{
+  int match = 0;
+  if (size == size_)
+  {
+    match = 1;
+    for (unsigned int i = 0; i < size_; i++)
+      if (data[i] != buffer_[i])
+      {
+        match = 0;
+        break;
+      }
+  }
+  if (!match && overwrite)
+    set(size, data);
+  return match;
+}
+
+
+void BlockCache::set(unsigned int size, const unsigned char *data)
+{
+  if (size_ < size)
+  {
+    delete[]buffer_;
+    buffer_ = new unsigned char[size];
+  }
+  size_ = size;
+  memcpy(buffer_, data, size);
+  checksum_ = checksum(size, data);
+}
+
+
+unsigned int BlockCache::checksum(unsigned int size, const unsigned char *data)
+{
+  unsigned int sum = 0;
+  unsigned int shift = 0;
+  const unsigned char *next = data;
+  for (unsigned int i = 0; i < size; i++)
+  {
+    unsigned int value = (unsigned int) *next++;
+    sum += (value << shift);
+    shift++;
+    if (shift == 8)
+      shift = 0;
+  }
+  return sum;
+}