65 lines
1.2 KiB
C
65 lines
1.2 KiB
C
/* Delta.c -- Delta converter
|
|
2009-05-26 : Igor Pavlov : Public domain */
|
|
|
|
#include "Precomp.h"
|
|
|
|
#include "Delta.h"
|
|
|
|
void Delta_Init(Byte *state)
|
|
{
|
|
unsigned i;
|
|
for (i = 0; i < DELTA_STATE_SIZE; i++)
|
|
state[i] = 0;
|
|
}
|
|
|
|
static void MyMemCpy(Byte *dest, const Byte *src, unsigned size)
|
|
{
|
|
unsigned i;
|
|
for (i = 0; i < size; i++)
|
|
dest[i] = src[i];
|
|
}
|
|
|
|
void Delta_Encode(Byte *state, unsigned delta, Byte *data, SizeT size)
|
|
{
|
|
Byte buf[DELTA_STATE_SIZE];
|
|
unsigned j = 0;
|
|
MyMemCpy(buf, state, delta);
|
|
{
|
|
SizeT i;
|
|
for (i = 0; i < size;)
|
|
{
|
|
for (j = 0; j < delta && i < size; i++, j++)
|
|
{
|
|
Byte b = data[i];
|
|
data[i] = (Byte)(b - buf[j]);
|
|
buf[j] = b;
|
|
}
|
|
}
|
|
}
|
|
if (j == delta)
|
|
j = 0;
|
|
MyMemCpy(state, buf + j, delta - j);
|
|
MyMemCpy(state + delta - j, buf, j);
|
|
}
|
|
|
|
void Delta_Decode(Byte *state, unsigned delta, Byte *data, SizeT size)
|
|
{
|
|
Byte buf[DELTA_STATE_SIZE];
|
|
unsigned j = 0;
|
|
MyMemCpy(buf, state, delta);
|
|
{
|
|
SizeT i;
|
|
for (i = 0; i < size;)
|
|
{
|
|
for (j = 0; j < delta && i < size; i++, j++)
|
|
{
|
|
buf[j] = data[i] = (Byte)(buf[j] + data[i]);
|
|
}
|
|
}
|
|
}
|
|
if (j == delta)
|
|
j = 0;
|
|
MyMemCpy(state, buf + j, delta - j);
|
|
MyMemCpy(state + delta - j, buf, j);
|
|
}
|