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-rwxr-xr-xCS/7zip/Common/CRC.cs55
1 files changed, 55 insertions, 0 deletions
diff --git a/CS/7zip/Common/CRC.cs b/CS/7zip/Common/CRC.cs
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index 0000000..62bb847
--- /dev/null
+++ b/CS/7zip/Common/CRC.cs
@@ -0,0 +1,55 @@
+// Common/CRC.cs
+
+namespace SevenZip
+{
+ class CRC
+ {
+ public static readonly uint[] Table;
+
+ static CRC()
+ {
+ Table = new uint[256];
+ const uint kPoly = 0xEDB88320;
+ for (uint i = 0; i < 256; i++)
+ {
+ uint r = i;
+ for (int j = 0; j < 8; j++)
+ if ((r & 1) != 0)
+ r = (r >> 1) ^ kPoly;
+ else
+ r >>= 1;
+ Table[i] = r;
+ }
+ }
+
+ uint _value = 0xFFFFFFFF;
+
+ public void Init() { _value = 0xFFFFFFFF; }
+
+ public void UpdateByte(byte b)
+ {
+ _value = Table[(((byte)(_value)) ^ b)] ^ (_value >> 8);
+ }
+
+ public void Update(byte[] data, uint offset, uint size)
+ {
+ for (uint i = 0; i < size; i++)
+ _value = Table[(((byte)(_value)) ^ data[offset + i])] ^ (_value >> 8);
+ }
+
+ public uint GetDigest() { return _value ^ 0xFFFFFFFF; }
+
+ static uint CalculateDigest(byte[] data, uint offset, uint size)
+ {
+ CRC crc = new CRC();
+ // crc.Init();
+ crc.Update(data, offset, size);
+ return crc.GetDigest();
+ }
+
+ static bool VerifyDigest(uint digest, byte[] data, uint offset, uint size)
+ {
+ return (CalculateDigest(data, offset, size) == digest);
+ }
+ }
+}