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