Engine directory for ticket #1

Engine/source/core/crc.cpp

@@ -0,0 +1,90 @@
+//-----------------------------------------------------------------------------
+// Copyright (c) 2012 GarageGames, LLC
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//-----------------------------------------------------------------------------
+
+#include "core/crc.h"
+
+#include "core/stream/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 CRC::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 CRC::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 = CRC::calculateCRC(buf, slen, crcVal);
+   }
+   stream->setPosition(0);
+   return(crcVal);
+}