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6827 | dunkaist | 1 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |
2 | ;; ;; |
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3 | ;; Copyright (C) KolibriOS team 2004-2017. All rights reserved. ;; |
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4 | ;; Distributed under terms of the GNU General Public License. ;; |
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5 | ;; ;; |
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6 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |
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7 | |||
8130 | dunkaist | 8 | $Revision: 8130 $ |
9 | |||
6827 | dunkaist | 10 | ; This crc32 routine doesn't use precomputed table to allow different |
11 | ; polynomials, which is the first param. |
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12 | ; Partial hash in assumed to be eax (both in and out). |
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13 | ; Usage: |
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14 | ; 1. mov eax, -1 |
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15 | ; 2. stdcall crypto.crc32 zero or more times |
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16 | ; 3. xor eax, -1 |
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17 | proc crc_32 _poly, _buffer, _length |
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18 | push ebx ecx edx esi |
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19 | |||
20 | mov esi, [_buffer] |
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21 | .next_byte: |
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22 | dec [_length] |
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23 | js .done |
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24 | movzx ebx, byte[esi] |
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25 | inc esi |
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26 | mov ecx, 8 |
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27 | .next_bit: |
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28 | mov edx, eax |
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29 | xor edx, ebx |
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30 | shr eax, 1 |
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31 | test edx, 1 |
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32 | jz @f |
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33 | xor eax, [_poly] |
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34 | @@: |
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35 | shr ebx, 1 |
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36 | dec ecx |
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37 | jnz .next_bit |
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38 | jmp .next_byte |
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39 | .done: |
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40 | pop esi edx ecx ebx |
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41 | ret |
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42 | endp |