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POPort C++ i_pwCalculateCRC16Continuation to C#
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  1. POPort C++ i_pwCalculateCRC16Continuation to C#
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    copied!<p>How to correctly convert the following C++ into C#?</p> <pre><code>//-------------------------------------------------------------------- // Calculate a 16-bit Cycle Redundency Check (CRC) value on a block of //data. // // Params: // pData : Pointer to data to calculate CRC. // dwSize : Size of data in bytes. // // Return: // 16-bit CRC value. // // Notes: //-------------------------------------------------------------------- private WORD i_pwCalculateCRC16Continuation(PBYTE pData, WORD dwSize, WORD wCRC) { // high byte of CRC initialized BYTE cCRCHi = (BYTE) ((wCRC &gt;&gt; 8) &amp; 0xFF); // low byte of CRC initialized BYTE cCRCLo = (BYTE) (wCRC &amp; 0xFF); // will index into CRC lookup table BYTE cIndex; while (dwSize--) // step through each byte of data { cIndex = cCRCHi ^ *pData++; // calculate the CRC cCRCHi = cCRCLo ^ m_cCRCHiArray[cIndex]; cCRCLo = m_cCRCLoArray[cIndex]; } return (cCRCHi &lt;&lt; 8) + cCRCLo; } </code></pre> <p>I found a tool that converted it but it were not perfect and it does not understand the context.</p> <pre><code>private ushort i_pwCalculateCRC16Continuation(ref byte pData, ushort dwSize, ushort wCRC) { byte cCRCHi = (byte) ((wCRC &gt;&gt; 8) &amp; 0xFF); byte cCRCLo = (byte) (wCRC &amp; 0xFF); byte cIndex; while (dwSize-- &gt; 0) { // Cannot convert source type 'int' to target type 'byte' cIndex = cCRCHi ^ pData++; // Cannot apply indexing to an expression of type 'byte' cCRCHi = cCRCLo ^ m_cCRCHiArray[cIndex]; // Cannot apply indexing to an expression of type 'byte' cCRCLo = m_cCRCLoArray[cIndex]; } // Cannot convert expression type 'int' to return type 'ushort' return (cCRCHi &lt;&lt; 8) + cCRCLo; } </code></pre> <p>The CRC concept and bit wise operations are little bit unfamiliar for me and I do not understand the above code well. Hence I do not know how to "fix" it.</p> <p>Thanks</p> <p><strong>EDIT:</strong> Missed the following variables.</p> <pre><code>private static byte[] m_cCRCHiArray = { 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x81, 0x40 }; private static byte[] m_cCRCLoArray = { 0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0x80, 0x40 }; </code></pre>
 

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