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 /*\r
  23  * Copyright (c) 2002 Sergey Chaban <serge@wildwestsoftware.com>\r
  24  */\r
  25 \r
  26 // see http://cvs.winehq.com/cvsweb/wine/dlls/imagehlp/modify.c\r
  27 // starting from Revision 1.8\r
  28 \r
  29 using System;\r
  30 using System.IO;\r
  31 \r
  32 namespace Mono.PEToolkit {\r
  33 \r
  34         public sealed class CheckSum {\r
  35 \r
  36                 private CheckSum()\r
  37                 {\r
  38                         // Never instantiated.\r
  39                 }\r
  40 \r
  41 \r
  42                 public static uint Calc(string peFile)\r
  43                 {\r
  44                         uint res = 0;\r
  45 \r
  46                         FileInfo pe = new FileInfo(peFile);\r
  47                         if (!pe.Exists) {\r
  48                                 throw new Exception("CheckSum : Invalid file path.");\r
  49                         }\r
  50 \r
  51                         using (BinaryReader reader = new BinaryReader(pe.OpenRead())) {\r
  52                                 if (!reader.BaseStream.CanSeek) {\r
  53                                         throw new Exception("Can't seek.");\r
  54                                 }\r
  55 \r
  56                                 DOSHeader dosHdr = new DOSHeader();\r
  57                                 COFFHeader coffHdr = new COFFHeader();\r
  58                                 PEHeader peHdr = new PEHeader();\r
  59 \r
  60                                 dosHdr.Read (reader);\r
  61                                 reader.BaseStream.Position = dosHdr.Lfanew;\r
  62                                 ExeSignature peSig = (ExeSignature) reader.ReadUInt16();\r
  63                                 if (peSig != ExeSignature.NT) {\r
  64                                         throw new BadImageException("Checksum : Invalid image format, cannot find PE signature.");\r
  65                                 }\r
  66         \r
  67                                 peSig = (ExeSignature) reader.ReadUInt16();\r
  68                                 if (peSig != ExeSignature.NT2) {\r
  69                                         throw new BadImageException("Checksum : Invalid image format, cannot find PE signature.");\r
  70                                 }\r
  71 \r
  72                                 coffHdr.Read(reader);\r
  73                                 peHdr.Read(reader);\r
  74 \r
  75                                 uint oldSum = peHdr.CheckSum;\r
  76                                 reader.BaseStream.Position = 0;\r
  77                                 long len = pe.Length;\r
  78                                 long whole = len >> 1;\r
  79                                 uint sum = 0;\r
  80                                 uint hi, lo;\r
  81                                 for (long i = whole; --i >= 0;) {\r
  82                                         sum += reader.ReadUInt16();\r
  83                                         hi = sum >> 16;\r
  84                                         if (hi != 0) {\r
  85                                                 sum = hi + (sum & 0xFFFF);\r
  86                                         }\r
  87                                 }\r
  88                                 if ((len & 1L) != 0) {\r
  89                                         sum += (uint) reader.ReadByte();\r
  90                                         hi = sum >> 16;\r
  91                                         if (hi != 0) {\r
  92                                                 sum = hi + (sum & 0xFFFF);\r
  93                                         }\r
  94                                 }\r
  95 \r
  96                                 // fix low word of checksum\r
  97                                 lo = oldSum & 0xFFFF;\r
  98                                 if ((sum & 0xFFFF) >= lo) {\r
  99                                         sum -= lo;\r
 100                                 } else {\r
 101                                         sum = (((sum & 0xFFFF) - lo) & 0xFFFF) - 1;\r
 102                                 }\r
 103 \r
 104                                 // fix high word of checksum\r
 105                                 hi = oldSum >> 16;\r
 106                                 if ((sum & 0xFFFF) >= hi) {\r
 107                                         sum -= hi;\r
 108                                 } else {\r
 109                                         sum = (((sum & 0xFFFF) - hi) & 0xFFFF) - 1;\r
 110                                 }\r
 111                         }\r
 112 \r
 113                         return res;\r
 114                 }\r
 115         }\r
 116 \r
 117 }\r