nel/3rdparty/seven_zip/Delta.c

   1 /* Delta.c -- Delta converter
   2 2009-05-26 : Igor Pavlov : Public domain */
   3
   4 #include "Precomp.h"
   5
   6 #include "Delta.h"
   7
   8 void Delta_Init(Byte *state)
   9 {
  10   unsigned i;
  11   for (i = 0; i < DELTA_STATE_SIZE; i++)
  12     state[i] = 0;
  13 }
  14
  15 static void MyMemCpy(Byte *dest, const Byte *src, unsigned size)
  16 {
  17   unsigned i;
  18   for (i = 0; i < size; i++)
  19     dest[i] = src[i];
  20 }
  21
  22 void Delta_Encode(Byte *state, unsigned delta, Byte *data, SizeT size)
  23 {
  24   Byte buf[DELTA_STATE_SIZE];
  25   unsigned j = 0;
  26   MyMemCpy(buf, state, delta);
  27   {
  28     SizeT i;
  29     for (i = 0; i < size;)
  30     {
  31       for (j = 0; j < delta && i < size; i++, j++)
  32       {
  33         Byte b = data[i];
  34         data[i] = (Byte)(b - buf[j]);
  35         buf[j] = b;
  36       }
  37     }
  38   }
  39   if (j == delta)
  40     j = 0;
  41   MyMemCpy(state, buf + j, delta - j);
  42   MyMemCpy(state + delta - j, buf, j);
  43 }
  44
  45 void Delta_Decode(Byte *state, unsigned delta, Byte *data, SizeT size)
  46 {
  47   Byte buf[DELTA_STATE_SIZE];
  48   unsigned j = 0;
  49   MyMemCpy(buf, state, delta);
  50   {
  51     SizeT i;
  52     for (i = 0; i < size;)
  53     {
  54       for (j = 0; j < delta && i < size; i++, j++)
  55       {
  56         buf[j] = data[i] = (Byte)(buf[j] + data[i]);
  57       }
  58     }
  59   }
  60   if (j == delta)
  61     j = 0;
  62   MyMemCpy(state, buf + j, delta - j);
  63   MyMemCpy(state + delta - j, buf, j);
  64 }