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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 5728 | serge | 1 | /* Delta.c -- Delta converter |
| 2 | 2009-05-26 : Igor Pavlov : Public domain */ |
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| 3 | |||
| 4 | #include "Precomp.h" |
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| 5 | |||
| 6 | #include "Delta.h" |
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| 7 | |||
| 8 | void Delta_Init(Byte *state) |
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| 9 | { |
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| 10 | unsigned i; |
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| 11 | for (i = 0; i < DELTA_STATE_SIZE; i++) |
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| 12 | state[i] = 0; |
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| 13 | } |
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| 14 | |||
| 15 | static void MyMemCpy(Byte *dest, const Byte *src, unsigned size) |
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| 16 | { |
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| 17 | unsigned i; |
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| 18 | for (i = 0; i < size; i++) |
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| 19 | dest[i] = src[i]; |
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| 20 | } |
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| 21 | |||
| 22 | void Delta_Encode(Byte *state, unsigned delta, Byte *data, SizeT size) |
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| 23 | { |
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| 24 | Byte buf[DELTA_STATE_SIZE]; |
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| 25 | unsigned j = 0; |
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| 26 | MyMemCpy(buf, state, delta); |
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| 27 | { |
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| 28 | SizeT i; |
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| 29 | for (i = 0; i < size;) |
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| 30 | { |
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| 31 | for (j = 0; j < delta && i < size; i++, j++) |
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| 32 | { |
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| 33 | Byte b = data[i]; |
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| 34 | data[i] = (Byte)(b - buf[j]); |
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| 35 | buf[j] = b; |
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| 36 | } |
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| 37 | } |
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| 38 | } |
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| 39 | if (j == delta) |
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| 40 | j = 0; |
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| 41 | MyMemCpy(state, buf + j, delta - j); |
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| 42 | MyMemCpy(state + delta - j, buf, j); |
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| 43 | } |
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| 44 | |||
| 45 | void Delta_Decode(Byte *state, unsigned delta, Byte *data, SizeT size) |
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| 46 | { |
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| 47 | Byte buf[DELTA_STATE_SIZE]; |
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| 48 | unsigned j = 0; |
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| 49 | MyMemCpy(buf, state, delta); |
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| 50 | { |
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| 51 | SizeT i; |
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| 52 | for (i = 0; i < size;) |
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| 53 | { |
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| 54 | for (j = 0; j < delta && i < size; i++, j++) |
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| 55 | { |
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| 56 | buf[j] = data[i] = (Byte)(buf[j] + data[i]); |
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| 57 | } |
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| 58 | } |
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| 59 | } |
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| 60 | if (j == delta) |
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| 61 | j = 0; |
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| 62 | MyMemCpy(state, buf + j, delta - j); |
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| 63 | MyMemCpy(state + delta - j, buf, j); |
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| 64 | } |