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>CRC Functions</TITLE
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>eCos Reference Manual</TH
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><DIV
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CLASS="CHAPTER"
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><H1
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><A
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NAME="CRC-FUNCTIONS">Chapter 50. CRC Functions</H1
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><DIV
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="SERVICES-CRC-API">CRC API</H1
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><P
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>The package implements a number of CRC functions as described below.
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The API to these functions is in the include file
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<TT
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CLASS="FILENAME"
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>cyg/crc/crc.h</TT
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>.</P
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="SERVICES-CRC-API-CYG-POSIX-CRC32">cyg_posix_crc32</H2
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><P
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>This function implements a 32 bit CRC which is compliant to the POSIX
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1008.2 Standard. This is the same as the Linux cksum program.</P
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><PRE
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CLASS="PROGRAMLISTING"
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>cyg_uint32 cyg_posix_crc32(unsigned char &#0042; s, int len);</PRE
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></TD
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></TR
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></TABLE
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><P
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>The CRC calculation is run over the data pointed to by
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<TT
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CLASS="PARAMETER"
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><I
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>s</I
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></TT
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>, of length <TT
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CLASS="PARAMETER"
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><I
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>len</I
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></TT
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>. The
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CRC is returned as an unsigned long.</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="SERVICES-CRC-API-CYG-CRC32">cyg_crc32</H2
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><P
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>These functions implement a 32 bit CRC by Gary S. Brown. They use the
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polynomial
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X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0.</P
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><PRE
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CLASS="PROGRAMLISTING"
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>cyg_uint32 cyg_crc32(unsigned char &#0042; s, int len);
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cyg_uint32 cyg_crc32_accumulate(cyg_uint32 crc, unsigned char &#0042; s, int len);</PRE
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></TD
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></TR
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></TABLE
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><P
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>The CRC calculation is run over the data pointed to by
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<TT
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CLASS="PARAMETER"
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><I
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>s</I
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></TT
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>, of length <TT
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CLASS="PARAMETER"
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><I
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>len</I
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></TT
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>. The
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CRC is returned as an unsigned long.</P
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><P
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> The CRC can be calculated over data separated into multiple
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buffers by using the function <TT
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CLASS="PARAMETER"
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><I
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> cyg_crc32_accumulate()</I
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></TT
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>. The parameter <TT
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CLASS="PARAMETER"
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><I
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>crc</I
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></TT
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> should be the
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result from the previous CRC calculation.</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="SERVICES-CRC-API-CYG-ETHER-CRC32">cyg_ether_crc32</H2
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><P
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>These functions implement the 32 bit CRC used by the Ethernet FCS word.</P
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><PRE
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CLASS="PROGRAMLISTING"
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>cyg_uint32 cyg_ether_crc32(unsigned char &#0042; s, int len);
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cyg_uint32 cyg_ether_crc32_accumulate(cyg_uint32 crc, unsigned char &#0042; s, int len);</PRE
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></TD
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></TR
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></TABLE
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><P
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>The CRC calculation is run over the data pointed to by
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<TT
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CLASS="PARAMETER"
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><I
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>s</I
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></TT
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>, of length <TT
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CLASS="PARAMETER"
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><I
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>len</I
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></TT
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>. The
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CRC is returned as an unsigned long.</P
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><P
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> The CRC can be calculated over data separated into multiple
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buffers by using the function <TT
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CLASS="PARAMETER"
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><I
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> cyg_ether_crc32_accumulate()</I
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></TT
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>. The parameter <TT
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CLASS="PARAMETER"
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><I
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>crc</I
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></TT
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> should be the
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result from the previous CRC calculation.</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="SERVICES-CRC-API-CYG-CRC16">cyg_crc16</H2
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><P
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>This function implements a 16 bit CRC. It uses the polynomial
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x^16+x^12+x^5+1.</P
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><PRE
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CLASS="PROGRAMLISTING"
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>cyg_uint16 cyg_crc16(unsigned char &#0042; s, int len);</PRE
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></TD
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></TR
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></TABLE
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><P
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>The CRC calculation is run over the data pointed to by
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<TT
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CLASS="PARAMETER"
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><I
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>s</I
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></TT
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>, of length <TT
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CLASS="PARAMETER"
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><I
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>len</I
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></TT
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>. The
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CRC is returned as an unsigned short.</P
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>CRC Algorithms</TD
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