Replace the CRC16-CCITT implementation with one generated by pycrc to be MIT compliant.

Checksums/ccitt.c

@@ -0,0 +1,53 @@
+/**
+ * \file ccitt.c
+ * Functions and types for CRC checks.
+ *
+ * Generated on Sun Oct 30 02:18:53 2016,
+ * by pycrc v0.9, https://pycrc.org
+ * using the configuration:
+ *    Width         = 16
+ *    Poly          = 0x1021
+ *    Xor_In        = 0xffff
+ *    ReflectIn     = False
+ *    Xor_Out       = 0x0000
+ *    ReflectOut    = False
+ *    Algorithm     = bit-by-bit-fast
+ *****************************************************************************/
+#include "ccitt.h"     /* include the header file generated with pycrc */
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+/**
+ * Update the crc value with new data.
+ *
+ * \param crc      The current crc value.
+ * \param data     Pointer to a buffer of \a data_len bytes.
+ * \param data_len Number of bytes in the \a data buffer.
+ * \return         The updated crc value.
+ *****************************************************************************/
+crc_t crc_update(crc_t crc, const void *data, size_t data_len)
+{
+    const unsigned char *d = (const unsigned char *)data;
+    unsigned int i;
+    bool bit;
+    unsigned char c;
+
+    while (data_len--) {
+        c = *d++;
+        for (i = 0x80; i > 0; i >>= 1) {
+            bit = crc & 0x8000;
+            if (c & i) {
+                bit = !bit;
+            }
+            crc <<= 1;
+            if (bit) {
+                crc ^= 0x1021;
+            }
+        }
+        crc &= 0xffff;
+    }
+    return crc & 0xffff;
+}
+
+

Checksums/ccitt.cs

@@ -0,0 +1,55 @@
+// C# port of the ccitt.c/ccitt.h files in this directory.
+// Original files generated by pycrc v0.9, https://pycrc.org
+
+namespace Checksums {
+	public static class Ccitt {
+		/**
+		 * Calculate the initial crc value.
+		 *
+		 * \return     The initial crc value.
+		 *****************************************************************************/
+		public static ushort Init() {
+			return 0xffff;
+		}
+
+		/**
+		 * Update the crc value with new data.
+		 *
+		 * \param crc      The current crc value.
+		 * \param data     Pointer to a buffer of \a data_len bytes.
+		 * \param data_len Number of bytes in the \a data buffer.
+		 * \return         The updated crc value.
+		 *****************************************************************************/
+		public static ushort Update( ushort crc, byte[] data, long data_len ) {
+			uint i;
+			bool bit;
+			byte c;
+
+			for ( long idx = 0; idx < data_len;  ++idx ) {
+				c = data[idx];
+				for ( i = 0x80; i > 0; i >>= 1 ) {
+					bit = ( crc & 0x8000 ) != 0;
+					if ( ( c & i ) != 0 ) {
+						bit = !bit;
+					}
+					crc <<= 1;
+					if ( bit ) {
+						crc ^= 0x1021;
+					}
+				}
+				crc &= 0xffff;
+			}
+			return (ushort)( crc & 0xffff );
+		}
+
+		/**
+		 * Calculate the final crc value.
+		 *
+		 * \param crc  The current crc value.
+		 * \return     The final crc value.
+		 *****************************************************************************/
+		public static ushort Finalize( ushort crc ) {
+			return (ushort)( crc ^ 0x0000 );
+		}
+	}
+}

Checksums/ccitt.h

@@ -0,0 +1,82 @@
+/**
+ * \file ccitt.h
+ * Functions and types for CRC checks.
+ *
+ * Generated on Sun Oct 30 02:18:48 2016,
+ * by pycrc v0.9, https://pycrc.org
+ * using the configuration:
+ *    Width         = 16
+ *    Poly          = 0x1021
+ *    Xor_In        = 0xffff
+ *    ReflectIn     = False
+ *    Xor_Out       = 0x0000
+ *    ReflectOut    = False
+ *    Algorithm     = bit-by-bit-fast
+ *****************************************************************************/
+#ifndef __CCITT_H__
+#define __CCITT_H__
+
+#include <stdlib.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/**
+ * The definition of the used algorithm.
+ *
+ * This is not used anywhere in the generated code, but it may be used by the
+ * application code to call algoritm-specific code, is desired.
+ *****************************************************************************/
+#define CRC_ALGO_BIT_BY_BIT_FAST 1
+
+
+/**
+ * The type of the CRC values.
+ *
+ * This type must be big enough to contain at least 16 bits.
+ *****************************************************************************/
+typedef uint_fast16_t crc_t;
+
+
+/**
+ * Calculate the initial crc value.
+ *
+ * \return     The initial crc value.
+ *****************************************************************************/
+static inline crc_t crc_init(void)
+{
+    return 0xffff;
+}
+
+
+/**
+ * Update the crc value with new data.
+ *
+ * \param crc      The current crc value.
+ * \param data     Pointer to a buffer of \a data_len bytes.
+ * \param data_len Number of bytes in the \a data buffer.
+ * \return         The updated crc value.
+ *****************************************************************************/
+crc_t crc_update(crc_t crc, const void *data, size_t data_len);
+
+
+/**
+ * Calculate the final crc value.
+ *
+ * \param crc  The current crc value.
+ * \return     The final crc value.
+ *****************************************************************************/
+static inline crc_t crc_finalize(crc_t crc)
+{
+    return crc ^ 0x0000;
+}
+
+
+#ifdef __cplusplus
+}           /* closing brace for extern "C" */
+#endif
+
+#endif      /* __CCITT_H__ */

Crc16Ccitt.cs

@@ -1,60 +0,0 @@
-// from http://www.sanity-free.com/133/crc_16_ccitt_in_csharp.html
-
-using System;
-
-namespace MysteryGiftConvert {
-	public enum InitialCrcValue { Zeros, NonZero1 = 0xffff, NonZero2 = 0x1D0F }
-
-	public class Crc16Ccitt {
-		private static Crc16Ccitt _StandardAlgorithm = null;
-		public static Crc16Ccitt StandardAlgorithm {
-			get {
-				if ( _StandardAlgorithm == null ) {
-					_StandardAlgorithm = new Crc16Ccitt( InitialCrcValue.NonZero1 );
-				}
-				return _StandardAlgorithm;
-			}
-		}
-
-		const ushort poly = 4129;
-		ushort[] table = new ushort[256];
-		ushort initialValue = 0;
-
-		public ushort ComputeChecksum( byte[] bytes ) {
-			return ComputeChecksum( bytes, 0, bytes.Length );
-		}
-		public ushort ComputeChecksum( byte[] bytes, int offset, int length ) {
-			ushort crc = this.initialValue;
-			for ( int i = 0; i < length; ++i ) {
-				crc = (ushort)( ( crc << 8 ) ^ table[( ( crc >> 8 ) ^ ( 0xff & bytes[offset + i] ) )] );
-			}
-			return crc;
-		}
-
-		public byte[] ComputeChecksumBytes( byte[] bytes ) {
-			return ComputeChecksumBytes( bytes, 0, bytes.Length );
-		}
-		public byte[] ComputeChecksumBytes( byte[] bytes, int offset, int length ) {
-			ushort crc = ComputeChecksum( bytes, offset, length );
-			return BitConverter.GetBytes( crc );
-		}
-
-		public Crc16Ccitt( InitialCrcValue initialValue ) {
-			this.initialValue = (ushort)initialValue;
-			ushort temp, a;
-			for ( int i = 0; i < table.Length; ++i ) {
-				temp = 0;
-				a = (ushort)( i << 8 );
-				for ( int j = 0; j < 8; ++j ) {
-					if ( ( ( temp ^ a ) & 0x8000 ) != 0 ) {
-						temp = (ushort)( ( temp << 1 ) ^ poly );
-					} else {
-						temp <<= 1;
-					}
-					a <<= 1;
-				}
-				table[i] = temp;
-			}
-		}
-	}
-}

MysteryGiftConvert.csproj

@@ -43,7 +43,7 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
-    <Compile Include="Crc16Ccitt.cs" />
+    <Compile Include="Checksums\ccitt.cs" />
     <Compile Include="MysteryGiftGen4.cs" />
     <Compile Include="MysteryGiftGen5.cs" />
     <Compile Include="Program.cs" />

Program.cs

@@ -115,7 +115,8 @@ namespace MysteryGiftConvert {
 					byte[] outfile = new byte[outStream.Length];
 					outStream.Read( outfile, 0, outfile.Length );
 					outStream.Position = outStream.Length;
-					outStream.Write( Crc16Ccitt.StandardAlgorithm.ComputeChecksumBytes( outfile ), 0, 2 );
+					ushort checksum = Checksums.Ccitt.Update( Checksums.Ccitt.Init(), outfile, outfile.LongLength );
+					outStream.Write( BitConverter.GetBytes( checksum ), 0, 2 );
 				}
 			} else {
 				Console.WriteLine( "Input is not a Generation 4 or 5 mystery gift file!" );