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Copy pathDelta.c
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169 lines (144 loc) · 2.82 KB
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/* Delta.c -- Delta converter
2021-02-09 : 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;
}
void Delta_Encode(Byte *state, unsigned delta, Byte *data, SizeT size)
{
Byte temp[DELTA_STATE_SIZE];
if (size == 0)
return;
{
unsigned i = 0;
do
temp[i] = state[i];
while (++i != delta);
}
if (size <= delta)
{
unsigned i = 0, k;
do
{
Byte b = *data;
*data++ = (Byte)(b - temp[i]);
temp[i] = b;
}
while (++i != size);
k = 0;
do
{
if (i == delta)
i = 0;
state[k] = temp[i++];
}
while (++k != delta);
return;
}
{
Byte *p = data + size - delta;
{
unsigned i = 0;
do
state[i] = *p++;
while (++i != delta);
}
{
const Byte *lim = data + delta;
ptrdiff_t dif = -(ptrdiff_t)delta;
if (((ptrdiff_t)size + dif) & 1)
{
--p; *p = (Byte)(*p - p[dif]);
}
while (p != lim)
{
--p; *p = (Byte)(*p - p[dif]);
--p; *p = (Byte)(*p - p[dif]);
}
dif = -dif;
do
{
--p; *p = (Byte)(*p - temp[--dif]);
}
while (dif != 0);
}
}
}
void Delta_Decode(Byte *state, unsigned delta, Byte *data, SizeT size)
{
unsigned i;
const Byte *lim;
if (size == 0)
return;
i = 0;
lim = data + size;
if (size <= delta)
{
do
*data = (Byte)(*data + state[i++]);
while (++data != lim);
for (; delta != i; state++, delta--)
*state = state[i];
data -= i;
}
else
{
/*
#define B(n) b ## n
#define I(n) Byte B(n) = state[n];
#define U(n) { B(n) = (Byte)((B(n)) + *data++); data[-1] = (B(n)); }
#define F(n) if (data != lim) { U(n) }
if (delta == 1)
{
I(0)
if ((lim - data) & 1) { U(0) }
while (data != lim) { U(0) U(0) }
data -= 1;
}
else if (delta == 2)
{
I(0) I(1)
lim -= 1; while (data < lim) { U(0) U(1) }
lim += 1; F(0)
data -= 2;
}
else if (delta == 3)
{
I(0) I(1) I(2)
lim -= 2; while (data < lim) { U(0) U(1) U(2) }
lim += 2; F(0) F(1)
data -= 3;
}
else if (delta == 4)
{
I(0) I(1) I(2) I(3)
lim -= 3; while (data < lim) { U(0) U(1) U(2) U(3) }
lim += 3; F(0) F(1) F(2)
data -= 4;
}
else
*/
{
do
{
*data = (Byte)(*data + state[i++]);
data++;
}
while (i != delta);
{
ptrdiff_t dif = -(ptrdiff_t)delta;
do
*data = (Byte)(*data + data[dif]);
while (++data != lim);
data += dif;
}
}
}
do
*state++ = *data;
while (++data != lim);
}