From 27474060e1287a67c45cd790d29b9095b35b2bdf Mon Sep 17 00:00:00 2001
From: ShizZy <shizzy@6bit.net>
Date: Thu, 29 Aug 2013 23:35:09 -0400
Subject: adding initial project layout

---
 src/common/src/crc.cpp | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 src/common/src/crc.cpp

(limited to 'src/common/src/crc.cpp')

diff --git a/src/common/src/crc.cpp b/src/common/src/crc.cpp
new file mode 100644
index 00000000..a36dfdad
--- /dev/null
+++ b/src/common/src/crc.cpp
@@ -0,0 +1,86 @@
+#include "common.h"
+#include "crc.h"
+
+u32	crc32_table[4][256];
+
+u32 Reflect(u32 ref, u8 Count)
+{
+     u32 value = 0;
+
+      // Swap bit 0 for bit 7
+      // bit 1 for bit 6, etc.
+      for(int i = 1; i < (Count + 1); i++)
+      {
+            if(ref & 1)
+                  value |= 1 << (Count - i);
+            ref >>= 1;
+      }
+      return value; 
+}
+
+void Init_CRC32_Table()
+{
+    // This is the official polynomial used by CRC-32
+    // in PKZip, WinZip and Ethernet.
+    u32 ulPolynomial = 0x04c11db7;
+
+    // 256 values representing ASCII character codes.
+	for(int x = 0; x < 4; x++)
+	{
+		for(int i = 0; i <= 0xFF; i++)
+		{
+			crc32_table[x][i]=Reflect(i, 8) << 24;
+			for (int j = 0; j < 8; j++)
+					crc32_table[x][i] = (crc32_table[x][i] << 1) ^ (crc32_table[x][i] & (1 << 31) ? (ulPolynomial + (x * 8)) : 0);
+			crc32_table[x][i] = Reflect(crc32_table[x][i], 32);
+		} 
+	}
+}
+
+u32 GenerateCRC(u8 *StartAddr, u32 len)
+{
+	u32  ulCRC = -1;
+
+	// Perform the algorithm on each character
+	// in the string, using the lookup table values.
+	for(; len > 7; len-=8)
+	{
+		ulCRC ^= *(u32 *)StartAddr;
+		ulCRC = crc32_table[3][((ulCRC) & 0xFF)] ^
+			    crc32_table[2][((ulCRC >> 8) & 0xFF)] ^
+			    crc32_table[1][((ulCRC >> 16) & 0xFF)] ^
+				crc32_table[0][((ulCRC >> 24))];
+		ulCRC ^= *(u32 *)(StartAddr + 4);
+		ulCRC = crc32_table[3][((ulCRC) & 0xFF)] ^
+			    crc32_table[2][((ulCRC >> 8) & 0xFF)] ^
+			    crc32_table[1][((ulCRC >> 16) & 0xFF)] ^
+				crc32_table[0][((ulCRC >> 24))];
+		StartAddr+=8;
+	}
+
+	if(len > 3)
+	{
+		ulCRC ^= *(u32 *)StartAddr;
+		ulCRC = crc32_table[3][((ulCRC) & 0xFF)] ^
+			    crc32_table[2][((ulCRC >> 8) & 0xFF)] ^
+			    crc32_table[1][((ulCRC >> 16) & 0xFF)] ^
+				crc32_table[0][((ulCRC >> 24))];
+		StartAddr+=4;
+		len -= 4;
+	}
+
+	switch(len)
+	{
+		case 3:
+			ulCRC = crc32_table[0][(ulCRC & 0xFF) ^ *StartAddr] ^ (ulCRC >> 8);
+			StartAddr++;
+		case 2:
+			ulCRC = crc32_table[0][(ulCRC & 0xFF) ^ *StartAddr] ^ (ulCRC >> 8);
+			StartAddr++;
+		case 1:
+			ulCRC = crc32_table[0][(ulCRC & 0xFF) ^ *StartAddr] ^ (ulCRC >> 8);
+			StartAddr++;
+	}
+
+	return ulCRC;
+}
-- 
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