mirror of
https://github.com/fadden/6502bench.git
synced 2024-12-24 22:31:56 +00:00
110 lines
4.0 KiB
C#
110 lines
4.0 KiB
C#
/*
|
|
* Copyright 2018 faddenSoft
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
using System;
|
|
using System.Diagnostics;
|
|
using System.IO;
|
|
|
|
namespace CommonUtil {
|
|
/// <summary>
|
|
/// Compute a standard CRC-32 (polynomial 0xedb88320, or
|
|
/// x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1).
|
|
/// </summary>
|
|
public static class CRC32 {
|
|
private static readonly uint[] sTable = ComputeTable();
|
|
|
|
private const uint INVERT = 0xffffffff;
|
|
|
|
/// <summary>
|
|
/// Generates 256-entry CRC table.
|
|
/// </summary>
|
|
/// <returns>Table.</returns>
|
|
private static uint[] ComputeTable() {
|
|
uint[] table = new uint[256];
|
|
|
|
uint poly = 0xedb88320;
|
|
for (int i = 0; i < 256; i++) {
|
|
uint val = (uint) i;
|
|
for (int j = 0; j < 8; j++) {
|
|
val = (val & 1) != 0 ? poly ^ (val >> 1) : val >> 1;
|
|
}
|
|
table[i] = val;
|
|
}
|
|
|
|
return table;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Computes a CRC on part of a buffer of data.
|
|
/// </summary>
|
|
/// <param name="crc">Previously computed CRC value. Initially zero.</param>
|
|
/// <param name="buffer">Data to compute CRC on.</param>
|
|
/// <param name="offset">Start offset within buffer.</param>
|
|
/// <param name="count">Number of bytes to process.</param>
|
|
/// <returns>New CRC value.</returns>
|
|
public static uint OnBuffer(uint crc, byte[] buffer, int offset, int count) {
|
|
crc = crc ^ INVERT;
|
|
while (count-- != 0) {
|
|
crc = sTable[(crc ^ buffer[offset]) & 0xff] ^ (crc >> 8);
|
|
offset++;
|
|
}
|
|
return crc ^ INVERT;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Computes a CRC on a buffer of data.
|
|
/// </summary>
|
|
/// <param name="crc">Previously computed CRC value. Initially zero.</param>
|
|
/// <param name="buffer">Data to compute CRC on.</param>
|
|
/// <returns>New CRC value.</returns>
|
|
public static uint OnWholeBuffer(uint crc, byte[] buffer) {
|
|
return OnBuffer(crc, buffer, 0, buffer.Length);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Computes a CRC on an entire file.
|
|
/// </summary>
|
|
/// <param name="pathName">Full path to file to open.</param>
|
|
/// <param name="ocrc">Receives the CRC.</param>
|
|
/// <returns>True on success, false on file error.</returns>
|
|
public static bool OnWholeFile(string pathName, out uint ocrc) {
|
|
try {
|
|
using (FileStream fs = File.Open(pathName, FileMode.Open, FileAccess.Read)) {
|
|
byte[] buffer = new byte[8192];
|
|
uint crc = 0;
|
|
long remain = fs.Length;
|
|
while (remain != 0) {
|
|
int toRead = (remain < buffer.Length) ? (int)remain : buffer.Length;
|
|
int actual = fs.Read(buffer, 0, toRead);
|
|
if (toRead != actual) {
|
|
throw new IOException("Expected " + toRead + ", got " + actual);
|
|
}
|
|
|
|
crc = OnBuffer(crc, buffer, 0, toRead);
|
|
remain -= toRead;
|
|
}
|
|
|
|
ocrc = crc;
|
|
return true;
|
|
}
|
|
} catch (IOException ioe) {
|
|
Debug.WriteLine("Fail: " + ioe);
|
|
ocrc = 0;
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
}
|