src/library/patch-ips.cpp

   1 #include "minmax.hpp"
   2 #include "patch.hpp"
   3 #include "serialization.hpp"
   4 #include "string.hpp"
   5 #include <cstdint>
   6 #include <limits>
   7 #include <cstring>
   8 #include <iostream>
   9
  10 namespace
  11 {
  12         uint8_t readbyte(const char* buf, uint64_t& pos, uint64_t size)
  13         {
  14                 if(pos >= size)
  15                         (stringfmt() << "Attempted to read byte past the end of patch (" << pos << " >= "
  16                                 << size << ").").throwex();
  17                 return static_cast<uint8_t>(buf[pos++]);
  18         }
  19
  20         struct ips_patcher : public rom_patcher
  21         {
  22                 ~ips_patcher() throw();
  23                 bool identify(const std::vector<char>& patch) throw();
  24                 void dopatch(std::vector<char>& out, const std::vector<char>& original,
  25                         const std::vector<char>& patch, int32_t offset) throw(std::bad_alloc, std::runtime_error);
  26         } ipspatch;
  27
  28         ips_patcher::~ips_patcher() throw()
  29         {
  30         }
  31
  32         bool ips_patcher::identify(const std::vector<char>& patch) throw()
  33         {
  34                 return (patch.size() > 5 && patch[0] == 'P' && patch[1] == 'A' && patch[2] == 'T' && patch[3] == 'C' &&
  35                         patch[4] == 'H');
  36         }
  37
  38         void ips_patcher::dopatch(std::vector<char>& out, const std::vector<char>& original,
  39                 const std::vector<char>& patch, int32_t offset) throw(std::bad_alloc, std::runtime_error)
  40         {
  41                 //Initial guess.
  42                 out = original;
  43                 const char* _patch = &patch[0];
  44                 size_t psize = patch.size();
  45
  46                 uint64_t ioffset = 5;
  47                 while(true) {
  48                         bool rle = false;
  49                         size_t left = patch.size() - ioffset;
  50                         uint8_t b;
  51                         uint32_t off = 0, l = 0;
  52                         off |= static_cast<uint32_t>(readbyte(_patch, ioffset, psize)) << 16;
  53                         off |= static_cast<uint32_t>(readbyte(_patch, ioffset, psize)) << 8;
  54                         off |= static_cast<uint32_t>(readbyte(_patch, ioffset, psize));
  55                         if(off == 0x454F46)
  56                                 break;  //EOF code.
  57                         l |= static_cast<uint32_t>(readbyte(_patch, ioffset, psize)) << 8;
  58                         l |= static_cast<uint32_t>(readbyte(_patch, ioffset, psize));
  59                         if(l == 0) {
  60                                 //RLE.
  61                                 l |= static_cast<uint32_t>(readbyte(_patch, ioffset, psize)) << 8;
  62                                 l |= static_cast<uint32_t>(readbyte(_patch, ioffset, psize));
  63                                 b = readbyte(_patch, ioffset, psize);
  64                                 rle = true;
  65                         }
  66                         uint64_t extra = 0;
  67                         if(offset >= 0)
  68                                 off += offset;
  69                         else {
  70                                 uint32_t noffset = static_cast<uint32_t>(-offset);
  71                                 uint32_t fromoff = min(noffset, off);
  72                                 off -= fromoff;
  73                                 extra = min(noffset - fromoff, l);
  74                                 l -= extra;
  75                         }
  76                         if(off + l >= out.size())
  77                                 out.resize(off + l);
  78                         if(!rle) {
  79                                 ioffset += extra;
  80                                 for(uint64_t i = 0; i < l; i++)
  81                                         out[off + i] = readbyte(_patch, ioffset, psize);
  82                         } else
  83                                 for(uint64_t i = 0; i < l; i++)
  84                                         out[off + i] = b;
  85                 }
  86         }
  87 }