aaru-dps/Aaru
1
0
Fork 0
mirror of https://github.com/aaru-dps/Aaru.git synced 2025-12-16 19:24:25 +00:00
Code Issues Packages Projects Releases Wiki Activity

Add support for custom CRC seed and polynomials.

Browse Source
This commit is contained in:
Natalia Portillo
2018-02-03 18:36:23 +00:00
parent 4f9d2fdb89
commit c06fc84348
3 changed files with 160 additions and 63 deletions
Download Patch File Download Diff File Expand all files Collapse all files

79
DiscImageChef.Checksums/CRC16Context.cs
View File

@@ -9,7 +9,7 @@
//
// --[ Description ] ----------------------------------------------------------
//
// Implements a CRC16-CCITT algorithm.
// Implements a CRC16 algorithm.
//
// --[ License ] --------------------------------------------------------------
//
@@ -37,22 +37,26 @@ using System.Text;
namespace DiscImageChef.Checksums
{
/// <summary>
/// Implements a CRC16-CCITT algorithm
/// Implements a CRC16 algorithm
/// </summary>
public class Crc16Context : IChecksum
{
const ushort CRC16_POLY = 0xA001;
const ushort CRC16_SEED = 0x0000;
public const ushort CRC16_IBM_POLY = 0xA001;
public const ushort CRC16_IBM_SEED = 0x0000;
public const ushort CRC16_CCITT_POLY = 0x8408;
public const ushort CRC16_CCITT_SEED = 0x0000;
readonly ushort finalSeed;
readonly ushort[] table;
ushort hashInt;
/// <summary>
/// Initializes the CRC16 table and seed
/// Initializes the CRC16 table and seed as CRC16-IBM
/// </summary>
public Crc16Context()
{
hashInt = CRC16_SEED;
hashInt = CRC16_IBM_SEED;
finalSeed = CRC16_IBM_SEED;
table = new ushort[256];
for(int i = 0; i < 256; i++)
@@ -60,7 +64,29 @@ namespace DiscImageChef.Checksums
ushort entry = (ushort)i;
for(int j = 0; j < 8; j++)
if((entry & 1) == 1)
entry = (ushort)((entry >> 1) ^ CRC16_POLY);
entry = (ushort)((entry >> 1) ^ CRC16_IBM_POLY);
else
entry = (ushort)(entry >> 1);
table[i] = entry;
}
}
/// <summary>
/// Initializes the CRC16 table with a custom polynomial and seed
/// </summary>
public Crc16Context(ushort polynomial, ushort seed)
{
hashInt = seed;
finalSeed = seed;
table = new ushort[256];
for(int i = 0; i < 256; i++)
{
ushort entry = (ushort)i;
for(int j = 0; j < 8; j++)
if((entry & 1) == 1)
entry = (ushort)((entry >> 1) ^ polynomial);
else
entry = (ushort)(entry >> 1);
@@ -93,7 +119,7 @@ namespace DiscImageChef.Checksums
public byte[] Final()
{
BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
return BigEndianBitConverter.GetBytes((ushort)(hashInt ^ CRC16_SEED));
return BigEndianBitConverter.GetBytes((ushort)(hashInt ^ finalSeed));
}
/// <summary>
@@ -104,8 +130,8 @@ namespace DiscImageChef.Checksums
StringBuilder crc16Output = new StringBuilder();
BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
for(int i = 0; i < BigEndianBitConverter.GetBytes((ushort)(hashInt ^ CRC16_SEED)).Length; i++)
crc16Output.Append(BigEndianBitConverter.GetBytes((ushort)(hashInt ^ CRC16_SEED))[i].ToString("x2"));
for(int i = 0; i < BigEndianBitConverter.GetBytes((ushort)(hashInt ^ finalSeed)).Length; i++)
crc16Output.Append(BigEndianBitConverter.GetBytes((ushort)(hashInt ^ finalSeed))[i].ToString("x2"));
return crc16Output.ToString();
}
@@ -127,10 +153,19 @@ namespace DiscImageChef.Checksums
/// <param name="hash">Byte array of the hash value.</param>
public static string File(string filename, out byte[] hash)
{
FileStream fileStream = new FileStream(filename, FileMode.Open);
ushort localhashInt;
return File(filename, out hash, CRC16_IBM_POLY, CRC16_IBM_SEED);
}
localhashInt = CRC16_SEED;
/// <summary>
/// Gets the hash of a file in hexadecimal and as a byte array.
/// </summary>
/// <param name="filename">File path.</param>
/// <param name="hash">Byte array of the hash value.</param>
public static string File(string filename, out byte[] hash, ushort polynomial, ushort seed)
{
FileStream fileStream = new FileStream(filename, FileMode.Open);
ushort localhashInt = seed;
ushort[] localTable = new ushort[256];
for(int i = 0; i < 256; i++)
@@ -138,7 +173,7 @@ namespace DiscImageChef.Checksums
ushort entry = (ushort)i;
for(int j = 0; j < 8; j++)
if((entry & 1) == 1)
entry = (ushort)((entry >> 1) ^ CRC16_POLY);
entry = (ushort)((entry >> 1) ^ polynomial);
else
entry = (ushort)(entry >> 1);
@@ -149,8 +184,9 @@ namespace DiscImageChef.Checksums
localhashInt =
(ushort)((localhashInt >> 8) ^ localTable[fileStream.ReadByte() ^ (localhashInt & 0xff)]);
BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
hash = BigEndianBitConverter.GetBytes(localhashInt);
localhashInt ^= seed;
BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
hash = BigEndianBitConverter.GetBytes(localhashInt);
StringBuilder crc16Output = new StringBuilder();
@@ -169,7 +205,7 @@ namespace DiscImageChef.Checksums
/// <param name="hash">Byte array of the hash value.</param>
public static string Data(byte[] data, uint len, out byte[] hash)
{
return Data(data, len, out hash, CRC16_POLY, CRC16_SEED);
return Data(data, len, out hash, CRC16_IBM_POLY, CRC16_IBM_SEED);
}
/// <summary>
@@ -182,9 +218,7 @@ namespace DiscImageChef.Checksums
/// <param name="seed">CRC seed</param>
public static string Data(byte[] data, uint len, out byte[] hash, ushort polynomial, ushort seed)
{
ushort localhashInt;
localhashInt = seed;
ushort localhashInt = seed;
ushort[] localTable = new ushort[256];
for(int i = 0; i < 256; i++)
@@ -202,8 +236,9 @@ namespace DiscImageChef.Checksums
for(int i = 0; i < len; i++)
localhashInt = (ushort)((localhashInt >> 8) ^ localTable[data[i] ^ (localhashInt & 0xff)]);
BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
hash = BigEndianBitConverter.GetBytes(localhashInt);
localhashInt ^= seed;
BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
hash = BigEndianBitConverter.GetBytes(localhashInt);
StringBuilder crc16Output = new StringBuilder();