mcs/class/Mono.PEToolkit/CheckSum.cs

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