tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
Log | Files | Refs | README | LICENSE

Delta.c (1337B)

      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 }