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/* Delta.c -- Delta converter
2009-05-26 : Igor Pavlov : Public domain */
#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);
}
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