aaru-dps/Aaru.Checksums
1
0
Fork 0
mirror of https://github.com/aaru-dps/Aaru.Checksums.git synced 2025-12-16 19:24:29 +00:00
Code Issues Packages Projects Releases Wiki Activity

Use zlib-inspired algorithm for Adler and Fletcher checksums.

Browse Source
This commit is contained in:
Natalia Portillo
2021-09-23 00:53:20 +01:00
parent 14e87c962b
commit d03d7082cc
2 changed files with 462 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files

176
Adler32Context.cs
View File

@@ -42,6 +42,7 @@ namespace Aaru.Checksums
public sealed class Adler32Context : IChecksum
{
const ushort ADLER_MODULE = 65521;
const uint NMAX = 5552;
ushort _sum1, _sum2;
/// <summary>Initializes the Adler-32 sums</summary>
@@ -55,14 +56,7 @@ namespace Aaru.Checksums
/// <summary>Updates the hash with data.</summary>
/// <param name="data">Data buffer.</param>
/// <param name="len">Length of buffer to hash.</param>
public void Update(byte[] data, uint len)
{
for(int i = 0; i < len; i++)
{
_sum1 = (ushort)((_sum1 + data[i]) % ADLER_MODULE);
_sum2 = (ushort)((_sum2 + _sum1) % ADLER_MODULE);
}
}
public void Update(byte[] data, uint len) => Step(ref _sum1, ref _sum2, data, len);
/// <inheritdoc />
/// <summary>Updates the hash with data.</summary>
@@ -91,6 +85,157 @@ namespace Aaru.Checksums
return adlerOutput.ToString();
}
static void Step(ref ushort preSum1, ref ushort preSum2, byte[] data, uint len)
{
uint sum1 = preSum1;
uint sum2 = preSum2;
uint n;
int dataOff = 0;
/* in case user likes doing a byte at a time, keep it fast */
if(len == 1)
{
sum1 += data[dataOff];
if(sum1 >= ADLER_MODULE)
sum1 -= ADLER_MODULE;
sum2 += sum1;
if(sum2 >= ADLER_MODULE)
sum2 -= ADLER_MODULE;
preSum1 = (ushort)(sum1 & 0xFFFF);
preSum2 = (ushort)(sum2 & 0xFFFF);
return;
}
/* in case short lengths are provided, keep it somewhat fast */
if(len < 16)
{
while(len-- > 0)
{
sum1 += data[dataOff++];
sum2 += sum1;
}
if(sum1 >= ADLER_MODULE)
sum1 -= ADLER_MODULE;
sum2 %= ADLER_MODULE; /* only added so many ADLER_MODULE's */
preSum1 = (ushort)(sum1 & 0xFFFF);
preSum2 = (ushort)(sum2 & 0xFFFF);
return;
}
/* do length NMAX blocks -- requires just one modulo operation */
while(len >= NMAX)
{
len -= NMAX;
n = NMAX / 16; /* NMAX is divisible by 16 */
do
{
sum1 += data[dataOff];
sum2 += sum1;
sum1 += data[dataOff + 1];
sum2 += sum1;
sum1 += data[dataOff + 2];
sum2 += sum1;
sum1 += data[dataOff + 2 + 1];
sum2 += sum1;
sum1 += data[dataOff + 4];
sum2 += sum1;
sum1 += data[dataOff + 4 + 1];
sum2 += sum1;
sum1 += data[dataOff + 4 + 2];
sum2 += sum1;
sum1 += data[dataOff + 4 + 2 + 1];
sum2 += sum1;
sum1 += data[dataOff + 8];
sum2 += sum1;
sum1 += data[dataOff + 8 + 1];
sum2 += sum1;
sum1 += data[dataOff + 8 + 2];
sum2 += sum1;
sum1 += data[dataOff + 8 + 2 + 1];
sum2 += sum1;
sum1 += data[dataOff + 8 + 4];
sum2 += sum1;
sum1 += data[dataOff + 8 + 4 + 1];
sum2 += sum1;
sum1 += data[dataOff + 8 + 4 + 2];
sum2 += sum1;
sum1 += data[dataOff + 8 + 4 + 2 + 1];
sum2 += sum1;
/* 16 sums unrolled */
dataOff += 16;
} while(--n != 0);
sum1 %= ADLER_MODULE;
sum2 %= ADLER_MODULE;
}
/* do remaining bytes (less than NMAX, still just one modulo) */
if(len != 0)
{
/* avoid modulos if none remaining */
while(len >= 16)
{
len -= 16;
sum1 += data[dataOff];
sum2 += sum1;
sum1 += data[dataOff + 1];
sum2 += sum1;
sum1 += data[dataOff + 2];
sum2 += sum1;
sum1 += data[dataOff + 2 + 1];
sum2 += sum1;
sum1 += data[dataOff + 4];
sum2 += sum1;
sum1 += data[dataOff + 4 + 1];
sum2 += sum1;
sum1 += data[dataOff + 4 + 2];
sum2 += sum1;
sum1 += data[dataOff + 4 + 2 + 1];
sum2 += sum1;
sum1 += data[dataOff + 8];
sum2 += sum1;
sum1 += data[dataOff + 8 + 1];
sum2 += sum1;
sum1 += data[dataOff + 8 + 2];
sum2 += sum1;
sum1 += data[dataOff + 8 + 2 + 1];
sum2 += sum1;
sum1 += data[dataOff + 8 + 4];
sum2 += sum1;
sum1 += data[dataOff + 8 + 4 + 1];
sum2 += sum1;
sum1 += data[dataOff + 8 + 4 + 2];
sum2 += sum1;
sum1 += data[dataOff + 8 + 4 + 2 + 1];
sum2 += sum1;
dataOff += 16;
}
while(len-- != 0)
{
sum1 += data[dataOff++];
sum2 += sum1;
}
sum1 %= ADLER_MODULE;
sum2 %= ADLER_MODULE;
}
preSum1 = (ushort)(sum1 & 0xFFFF);
preSum2 = (ushort)(sum2 & 0xFFFF);
}
/// <summary>Gets the hash of a file</summary>
/// <param name="filename">File path.</param>
public static byte[] File(string filename)
@@ -110,10 +255,13 @@ namespace Aaru.Checksums
ushort localSum1 = 1;
ushort localSum2 = 0;
for(int i = 0; i < fileStream.Length; i++)
byte[] buffer = new byte[65536];
int read = fileStream.Read(buffer, 0, 65536);
while(read > 0)
{
localSum1 = (ushort)((localSum1 + fileStream.ReadByte()) % ADLER_MODULE);
localSum2 = (ushort)((localSum2 + localSum1) % ADLER_MODULE);
Step(ref localSum1, ref localSum2, buffer, (uint)read);
read = fileStream.Read(buffer, 0, 65536);
}
uint finalSum = (uint)((localSum2 << 16) | localSum1);
@@ -139,11 +287,7 @@ namespace Aaru.Checksums
ushort localSum1 = 1;
ushort localSum2 = 0;
for(int i = 0; i < len; i++)
{
localSum1 = (ushort)((localSum1 + data[i]) % ADLER_MODULE);
localSum2 = (ushort)((localSum2 + localSum1) % ADLER_MODULE);
}
Step(ref localSum1, ref localSum2, data, len);
uint finalSum = (uint)((localSum2 << 16) | localSum1);