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From Justin Erenkrantz <jerenkra...@ebuilt.com>
Subject Re: cvs commit: apr/network_io/unix sendrecv.c
Date Wed, 25 Jul 2001 15:49:54 GMT
On Wed, Jul 25, 2001 at 08:38:02AM -0700, Ryan Bloom wrote:
> 
> We usually don't cast for cases like this.  If a cast is required, then something is
> usually wrong.

I don't like casting, but the types just don't match up in any way.

With Solaris' sendfilev, you use a sendfilevec_t struct:

/*
 * Structure used by sendfilev()
 */
typedef struct sendfilevec {
        int             sfv_fd;
        uint_t          sfv_flag;
        off_t           sfv_off;
        size_t          sfv_len;
} sendfilevec_t;

Solaris defines the iovecs as:

#if     defined(_XPG4_2)
typedef struct iovec {
        void    *iov_base;
        size_t  iov_len;
} iovec_t;
#else
typedef struct iovec {
        caddr_t iov_base;
#if defined(_LP64)
        size_t  iov_len;
#else
        long    iov_len;
#endif
} iovec_t;
#endif  /* defined(_XPG4_2) */

which I believe condenses down into:

typedef struct iovec {
        caddr_t iov_base;
        long    iov_len;
} iovec_t;

And a caddr_t is:

typedef char            *caddr_t;       /* ?<core address> type */

We want to pass the address of the iov_base pointer to sendfilev
via the off_t (Solaris knows that it is a pointer to our address
space via a special fd).  Since, off_t refers to an offset in our 
own memory space and it isn't a pointer, well....

This just seems to be a Solaris-specific wackiness.  Any tips on 
how to avoid this are appreciated.  I just couldn't think of any.  
-- justin


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