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Generalized Crc32 implementation so it can be used for LG (TLL), Panasonic (.bin and .db) and Sony (sdb.xml)

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This commit is contained in:
hbeham
2019-07-20 02:08:51 +02:00
parent 8e6d32e557
commit 1e26ef9cd4
4 changed files with 68 additions and 320 deletions
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77
source/ChanSort.Api/Utils/Crc32.cs
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@@ -1,45 +1,92 @@
namespace ChanSort.Api
{
public static class Crc32
public class Crc32
{
private const uint CrcMask = 0xFFFFFFFF;
private const uint CrcPoly = 0xEDB88320;
// This implementation is MSB-first based, using left-shift operators and a polynomial of 0x04C11DB7
// To get the same CRC32 values that an LSB-first implementation with polynomial 0xEDB88320 would produce,
// all bits in the input bytes and the resulting crc need to be reversed (msb to lsb)
private static readonly uint[] crc32Table;
private const uint CrcMask = 0xFFFFFFFF;
private const uint CrcPoly = 0x04C11DB7;
public static Crc32 Normal = new Crc32(true);
public static Crc32 Reversed = new Crc32(false);
private static readonly byte[] BitReversedBytes = new byte[256];
private readonly uint[] crc32Table;
private readonly bool msbFirst;
#region static initializers
static Crc32()
{
crc32Table = InitCrc32Table();
InitCrc32Table();
InitReversedBitOrderTable();
}
private static void InitReversedBitOrderTable()
{
for (int i = 0; i < 256; i++)
{
byte v = 0;
for (int j = 0, m = i; j < 8; j++, m >>= 1)
{
v <<= 1;
if ((m & 1) != 0)
v |= 0x01;
}
BitReversedBytes[i] = v;
}
}
#region InitCrc32Table()
private static uint[] InitCrc32Table()
{
var crcTable = new uint[256];
var poly = CrcPoly;
for (uint i = 0; i < 256; i++)
{
uint r = i;
for (uint j = 8; j > 0; j--)
uint r = i << 24;
for (uint j = 0; j < 8; j++)
{
if ((r & 1) == 1)
r = ((r >> 1) ^ CrcPoly);
if ((r & 0x80000000) != 0)
r = (r << 1) ^ poly;
else
r >>= 1;
r <<= 1;
}
crcTable[i] = r;
}
return crcTable;
}
#endregion
/// <param name="msbFirst">true for using the "left shift" MSB-first algorithm with polynomial 0x04C11Db7. false to use "right shift" with polynomial 0xEDB883320</param>
public Crc32(bool msbFirst = true)
{
this.msbFirst = msbFirst;
crc32Table = InitCrc32Table();
}
#region CalcCrc32()
public static uint CalcCrc32(byte[] block, int start, int length)
public uint CalcCrc32(byte[] data, int start, int length)
{
uint crc32 = CrcMask;
for (int i = 0; i < length; i++)
crc32 = crc32Table[(crc32 & 0xff) ^ block[start + i]] ^ (crc32 >> 8);
return crc32;
{
var b = data[start + i];
if (!this.msbFirst)
b = BitReversedBytes[b];
crc32 = (crc32 << 8) ^ crc32Table[((crc32 >> 24) ^ b) & 0xFF];
}
if (this.msbFirst)
return crc32;
// reverse all bits to make MSB <-> LSB
return (uint) BitReversedBytes[crc32 >> 24] | ((uint) BitReversedBytes[(crc32 >> 16) & 0xFF] << 8) | ((uint) BitReversedBytes[(crc32 >> 8) & 0xFF] << 16) | ((uint) BitReversedBytes[crc32 & 0xFF] << 24);
}
#endregion
@@ -52,7 +99,7 @@
{
if (crc32 == checksum)
return i;
crc32 = crc32Table[(crc32 & 0xff) ^ block[i]] ^ (crc32 >> 8);
crc32 = (crc32 >> 8) ^ crc32Table[(crc32 >> 24) ^ block[i]];
}
return 0;
}