67 lines
1.9 KiB
MQL5
67 lines
1.9 KiB
MQL5
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//+------------------------------------------------------------------+
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//| CRC32.mqh |
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//| Copyright 2021, MetaQuotes Ltd. |
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//| https://www.mql5.com |
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//| Zip, PNG, etc |
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//+------------------------------------------------------------------+
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//+------------------------------------------------------------------+
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//| Calculate CRC32 in most simple way |
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//+------------------------------------------------------------------+
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class CRC32
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{
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private:
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static uint table[256]; // bit mask per byte
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static void initTable()
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{
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static bool tableCalculated = false;
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if(tableCalculated) return;
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tableCalculated = true;
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const uint polynomial = 0xEDB88320;
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// loop through all possible byte values
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for(int i = 0; i < 256; ++i)
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{
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uint byte = (uint)i;
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// loop through bits
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for(uchar b = 0; b < 8; ++b)
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{
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if((byte & 1) != 0)
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{
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byte = polynomial ^ (byte >> 1);
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}
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else
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{
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byte = (byte >> 1);
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}
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}
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table[i] = byte;
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}
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}
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public:
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CRC32() { initTable(); }
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uint compute(uchar &bytes[], uint crc = 0xFFFFFFFF)
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{
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for(int i = 0; i < ArraySize(bytes); ++i)
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{
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uchar pos = (uchar)((crc ^ bytes[i]) & 0xFF);
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crc = (uint)((crc >> 8) ^ (uint)(table[pos]));
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}
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return crc;
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}
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static uint crc32(uchar &bytes[])
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{
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CRC32 temp;
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return temp.compute(bytes) ^ 0xFFFFFFFF;
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}
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};
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static uint CRC32::table[256];
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//+------------------------------------------------------------------+
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