Initial commit

Torque/SDK/engine/core/crc.cc

@@ -0,0 +1,72 @@
+//-----------------------------------------------------------------------------
+// Torque Game Engine
+// Copyright (C) GarageGames.com, Inc.
+//-----------------------------------------------------------------------------
+
+#include "platform/platform.h"
+#include "core/stream.h"
+
+//-----------------------------------------------------------------------------
+// simple crc function - generates lookup table on first call
+
+static U32 crcTable[256];
+static bool crcTableValid;
+
+static void calculateCRCTable()
+{
+   U32 val;
+
+   for(S32 i = 0; i < 256; i++)
+   {
+      val = i;
+      for(S32 j = 0; j < 8; j++)
+      {
+         if(val & 0x01)
+            val = 0xedb88320 ^ (val >> 1);
+         else
+            val = val >> 1;
+      }
+      crcTable[i] = val;
+   }
+
+   crcTableValid = true;
+}
+
+
+//-----------------------------------------------------------------------------
+
+U32 calculateCRC(const void * buffer, S32 len, U32 crcVal )
+{
+   // check if need to generate the crc table
+   if(!crcTableValid)
+      calculateCRCTable();
+
+   // now calculate the crc
+   char * buf = (char*)buffer;
+   for(S32 i = 0; i < len; i++)
+      crcVal = crcTable[(crcVal ^ buf[i]) & 0xff] ^ (crcVal >> 8);
+   return(crcVal);
+}
+
+U32 calculateCRCStream(Stream *stream, U32 crcVal )
+{
+   // check if need to generate the crc table
+   if(!crcTableValid)
+      calculateCRCTable();
+
+   // now calculate the crc
+   stream->setPosition(0);
+   S32 len = stream->getStreamSize();
+   U8 buf[4096];
+
+   S32 segCount = (len + 4095) / 4096;
+
+   for(S32 j = 0; j < segCount; j++)
+   {
+      S32 slen = getMin(4096, len - (j * 4096));
+      stream->read(slen, buf);
+      crcVal = calculateCRC(buf, slen, crcVal);
+   }
+   stream->setPosition(0);
+   return(crcVal);
+}