[lwip-users] Re: [lwip] Re: lwIP on DSPs

[leon . woestenberg]

Hello all,

in response to Bill Knight; my stack indeed uses macro's (#define's) that
pack and unpack bytes into/out of 16-bit words.

The reason was a hardware legacy, some hardware design of ours did not have
individual byte accesses enabled,
and acted on 16-bit words. In fact, I'm planning to remove these #define's
as we need to redesign the hardware anyway.

Regards,

Leon Woestenberg

Axon Digital Design
Phone: +31 13 511 6666
Fax: +31 13 511 4151
web: www.axon.tv

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                    "Bill Knight"                                               
                                    
                    <address@hidden       To:     "address@hidden" 
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                    Sent by:             Subject:     Re: [lwip] Re: lwIP on 
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                    03-12-01 20:53                                              
                                    
                    Please respond                                              
                                    
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#define TCPH_SRC(hdr) (hdr)->src
#define TCPH_DEST(hdr) (hdr)->dest
#define TCPH_OFFSET(hdr) (ntohs((hdr)->offset_flags) >> 8)
#define TCPH_FLAGS(hdr) (ntohs((hdr)->offset_flags) & 0xff)
#define /* etc.*/

For a DSP with 32-bit chars, the equivalent (but a lot trickier) struct and

#defines could be done. This way, the actual protocol code wouldn't have to

be changed in any way. A single #define in arch/cpu.h or arch/cc.h would
change they way the protocol headers are defined.

Leon, your DHCP and ARP code used #defines in this way to extract header
field values, perhaps you can comment on the above. Does your entire stack
work this way? Were there any particular reson for doing it that way or for

doing it the struct way (such as lwIP)?

In any case, this is a good thing to put into lwIP 0.6.

/adam


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