src/serialization.cpp

   1 /*
   2 (c) 2010 Perttu Ahola <celeron55@gmail.com>
   3 */
   4
   5 #include "serialization.h"
   6 #include "utility.h"
   7
   8 void compress(SharedBuffer<u8> data, std::ostream &os, u8 version)
   9 {
  10         if(data.getSize() == 0)
  11                 return;
  12
  13         // Write length (u32)
  14
  15         u8 tmp[4];
  16         writeU32(tmp, data.getSize());
  17         os.write((char*)tmp, 4);
  18
  19         // We will be writing 8-bit pairs of more_count and byte
  20         u8 more_count = 0;
  21         u8 current_byte = data[0];
  22         for(u32 i=1; i<data.getSize(); i++)
  23         {
  24                 if(
  25                         data[i] != current_byte
  26                         || more_count == 255
  27                 )
  28                 {
  29                         // write count and byte
  30                         os.write((char*)&more_count, 1);
  31                         os.write((char*)&current_byte, 1);
  32                         more_count = 0;
  33                         current_byte = data[i];
  34                 }
  35                 else
  36                 {
  37                         more_count++;
  38                 }
  39         }
  40         // write count and byte
  41         os.write((char*)&more_count, 1);
  42         os.write((char*)&current_byte, 1);
  43 }
  44
  45 void decompress(std::istream &is, std::ostream &os, u8 version)
  46 {
  47         // Read length (u32)
  48
  49         u8 tmp[4];
  50         is.read((char*)tmp, 4);
  51         u32 len = readU32(tmp);
  52
  53         // We will be reading 8-bit pairs of more_count and byte
  54         u32 count = 0;
  55         for(;;)
  56         {
  57                 u8 more_count=0;
  58                 u8 byte=0;
  59
  60                 is.read((char*)&more_count, 1);
  61
  62                 is.read((char*)&byte, 1);
  63
  64                 if(is.eof())
  65                         throw SerializationError("decompress: stream ended halfway");
  66
  67                 for(s32 i=0; i<(u16)more_count+1; i++)
  68                         os.write((char*)&byte, 1);
  69
  70                 count += (u16)more_count+1;
  71
  72                 if(count == len)
  73                         break;
  74         }
  75 }
  76
  77