Re: [9fans] ntohl, htonl, &c

[Alex Musolino <alex@musolino.id.au>]

> I'm getting rid of ape but I need the functions at
> /sys/src/ape/lib/bsd/ntohl.c to port some software.  These functions
> just change endianness.  Is there some native similar functions
> somebody is aware of?  lookman is not helping me here.  I don't want
> to add code if a similar functionality is already in the system.

No. Those functions are mental.  The Plan 9 way is so simple that
there's no library, everyone just brings their own macros/functions.
The trick is: if you care about the order of bytes then you should be
dealing with a byte array, not a native integral type.

These are from Ori's git implementation though there are other,
similar implementations around the place (e.g. lib9p, venti).  They
do the job perfectly well.

#define GETBE32(b) \
        ((((b)[0] & 0xFFul) << 24) | \
         (((b)[1] & 0xFFul) << 16) | \
         (((b)[2] & 0xFFul) <<  8) | \
         (((b)[3] & 0xFFul) <<  0))

#define PUTBE32(b, n)\
        do{ \
                (b)[0] = (n) >> 24; \
                (b)[1] = (n) >> 16; \
                (b)[2] = (n) >> 8; \
                (b)[3] = (n) >> 0; \
        } while(0)

Little endian versions proceed similarly:

#define GETLE32(b) \
        ((((b)[0] & 0xFFul) <<  0) | \
         (((b)[1] & 0xFFul) <<  8) | \
         (((b)[2] & 0xFFul) << 16) | \
         (((b)[3] & 0xFFul) << 24))

#define PUTLE32(b, n)\
        do{ \
                (b)[0] = (n) >> 0; \
                (b)[1] = (n) >> 8; \
                (b)[2] = (n) >> 16; \
                (b)[3] = (n) >> 24; \
        } while(0)

The 16-bit and 64-bit versions should be obvious.

For porting I'd just use APE, or copy the bits and pieces you need.


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