using System; namespace PKHeX.Core { /// /// Checksum algorithms used by the games. /// public static class Checksums { /// Calculates the CRC16-CCITT checksum over an input byte array. /// Input byte array /// Starting point for checksum /// /// Checksum public static ushort CRC16_CCITT(byte[] data, int start, int length) { byte top = 0xFF; byte bot = 0xFF; int end = start + length; for (int i = start; i < end; i++) { var x = data[i] ^ top; x ^= (x >> 4); top = (byte)(bot ^ (x >> 3) ^ (x << 4)); bot = (byte)(x ^ (x << 5)); } return (ushort)(top << 8 | bot); } /// Calculates the CRC16-CCITT checksum over an input byte array. /// Input byte array /// Checksum public static ushort CRC16_CCITT(byte[] data) => CRC16_CCITT(data, 0, data.Length); private static readonly ushort[] crc16 = { 0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241, 0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440, 0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40, 0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841, 0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40, 0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41, 0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641, 0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040, 0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240, 0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441, 0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41, 0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840, 0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41, 0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40, 0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640, 0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041, 0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240, 0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441, 0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41, 0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840, 0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41, 0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40, 0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640, 0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041, 0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241, 0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440, 0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40, 0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841, 0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40, 0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41, 0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641, 0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040 }; /// Calculates the 16bit checksum over an input byte array. /// Input byte array /// Offset to start checksum at /// Length of array to checksum /// Initial value for checksum /// Checksum public static ushort CRC16(byte[] data, int start, int length, ushort initial) { ushort chk = initial; for (var i = start; i < start + length; i++) chk = (ushort)(crc16[(data[i] ^ chk) & 0xFF] ^ chk >> 8); return chk; } /// Calculates the 16bit checksum over an input byte array. /// Input byte array /// Offset to start checksum at /// Length of array to checksum /// Checksum public static ushort CRC16(byte[] data, int start, int length) => (ushort)~CRC16(data, start, length, unchecked((ushort)~0)); /// Calculates the 16bit checksum over an input byte array. /// Input byte array /// Offset to start checksum at /// Length of array to checksum /// Checksum public static ushort CRC16NoInvert(byte[] data, int start, int length) => CRC16(data, start, length, 0); /// Calculates the 32bit checksum over an input byte array. Used in GBA save files. /// Input byte array /// Offset to start checksum at /// Length of array to checksum /// Initial value for checksum /// Checksum public static ushort CheckSum32(byte[] data, int start, int length, uint initial = 0) { uint val = initial; for (int i = start; i < start + length; i += 4) val += BitConverter.ToUInt32(data, i); return (ushort)(val + (val >> 16)); } /// Calculates the 16bit checksum over an input byte array. Used in N64 Stadium save files. /// Input byte array /// Offset to start checksum at /// Length of array to checksum /// Initial value for checksum /// Checksum public static ushort CheckSum16(byte[] data, int start, int length, ushort initial = 0) { ushort acc = initial; for (int i = 0; i < length; i++) acc += data[start + i]; return acc; } /// Calculates the 32bit checksum over an input byte array. Used in GBA save files. /// Input byte array /// Initial value for checksum /// Checksum public static ushort CheckSum32(byte[] data, uint initial = 0) => CheckSum32(data, 0, data.Length, initial); /// Calculates the 32bit checksum over an input byte array. Used in GC R/S BOX. /// Input byte array /// Offset to start checksum at /// Exclusive end offset to finish the checksum at /// Checksum public static uint CheckSum16BigInvert(byte[] data, int start, int end) { ushort chk = 0; // initial value for (int i = start; i < end; i += 2) chk += BigEndian.ToUInt16(data, i); return (uint)(chk << 16 | (ushort)(0xF004 - chk)); } } }