mcs/class/Mono.PEToolkit/CheckSum.cs

   1
   2 //
   3 // Permission is hereby granted, free of charge, to any person obtaining
   4 // a copy of this software and associated documentation files (the
   5 // "Software"), to deal in the Software without restriction, including
   6 // without limitation the rights to use, copy, modify, merge, publish,
   7 // distribute, sublicense, and/or sell copies of the Software, and to
   8 // permit persons to whom the Software is furnished to do so, subject to
   9 // the following conditions:
  10 //
  11 // The above copyright notice and this permission notice shall be
  12 // included in all copies or substantial portions of the Software.
  13 //
  14 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  15 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  16 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  17 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  18 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  19 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  20 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  21 //
  22 /*
  23  * Copyright (c) 2002 Sergey Chaban <serge@wildwestsoftware.com>
  24  */
  25
  26 // see http://cvs.winehq.com/cvsweb/wine/dlls/imagehlp/modify.c
  27 // starting from Revision 1.8
  28
  29 using System;
  30 using System.IO;
  31
  32 namespace Mono.PEToolkit {
  33
  34         public sealed class CheckSum {
  35
  36                 private CheckSum()
  37                 {
  38                         // Never instantiated.
  39                 }
  40
  41
  42                 public static uint Calc(string peFile)
  43                 {
  44                         uint res = 0;
  45
  46                         FileInfo pe = new FileInfo(peFile);
  47                         if (!pe.Exists) {
  48                                 throw new Exception("CheckSum : Invalid file path.");
  49                         }
  50
  51                         using (BinaryReader reader = new BinaryReader(pe.OpenRead())) {
  52                                 if (!reader.BaseStream.CanSeek) {
  53                                         throw new Exception("Can't seek.");
  54                                 }
  55
  56                                 DOSHeader dosHdr = new DOSHeader();
  57                                 COFFHeader coffHdr = new COFFHeader();
  58                                 PEHeader peHdr = new PEHeader();
  59
  60                                 dosHdr.Read (reader);
  61                                 reader.BaseStream.Position = dosHdr.Lfanew;
  62                                 ExeSignature peSig = (ExeSignature) reader.ReadUInt16();
  63                                 if (peSig != ExeSignature.NT) {
  64                                         throw new BadImageException("Checksum : Invalid image format, cannot find PE signature.");
  65                                 }
  66
  67                                 peSig = (ExeSignature) reader.ReadUInt16();
  68                                 if (peSig != ExeSignature.NT2) {
  69                                         throw new BadImageException("Checksum : Invalid image format, cannot find PE signature.");
  70                                 }
  71
  72                                 coffHdr.Read(reader);
  73                                 peHdr.Read(reader);
  74
  75                                 uint oldSum = peHdr.CheckSum;
  76                                 reader.BaseStream.Position = 0;
  77                                 long len = pe.Length;
  78                                 long whole = len >> 1;
  79                                 uint sum = 0;
  80                                 uint hi, lo;
  81                                 for (long i = whole; --i >= 0;) {
  82                                         sum += reader.ReadUInt16();
  83                                         hi = sum >> 16;
  84                                         if (hi != 0) {
  85                                                 sum = hi + (sum & 0xFFFF);
  86                                         }
  87                                 }
  88                                 if ((len & 1L) != 0) {
  89                                         sum += (uint) reader.ReadByte();
  90                                         hi = sum >> 16;
  91                                         if (hi != 0) {
  92                                                 sum = hi + (sum & 0xFFFF);
  93                                         }
  94                                 }
  95
  96                                 // fix low word of checksum
  97                                 lo = oldSum & 0xFFFF;
  98                                 if ((sum & 0xFFFF) >= lo) {
  99                                         sum -= lo;
 100                                 } else {
 101                                         sum = (((sum & 0xFFFF) - lo) & 0xFFFF) - 1;
 102                                 }
 103
 104                                 // fix high word of checksum
 105                                 hi = oldSum >> 16;
 106                                 if ((sum & 0xFFFF) >= hi) {
 107                                         sum -= hi;
 108                                 } else {
 109                                         sum = (((sum & 0xFFFF) - hi) & 0xFFFF) - 1;
 110                                 }
 111                         }
 112
 113                         return res;
 114                 }
 115         }
 116
 117 }