From: Lou Vanek <vanek@...>
Date: 2006-02-12T22:47:08+09:00
Subject: Re: ruby/dl question

Eric Hodel wrote:
> On Feb 10, 2006, at 7:30 PM, ara.t.howard@noaa.gov wrote:
> 
>> if one has:
>>
>>  struct flock {
>>      ...
>>      short l_type;    /* Type of lock: F_RDLCK,
>>                          F_WRLCK, F_UNLCK */
>>      short l_whence;  /* How to interpret l_start:
>>                          SEEK_SET, SEEK_CUR, SEEK_END */
>>      off_t l_start;   /* Starting offset for lock */
>>      off_t l_len;     /* Number of bytes to lock */
>>      pid_t l_pid;     /* PID of process blocking our lock
>>                          (F_GETLK only) */
>>      ...
>>  };
>>
>> can this structure be desribed using ruby/dl?  i'm worried that the  
>> struct
>> method assumes the fields are in order which, in the case of the flock
>> structure, they may not be.
> 
> 
> You have a bigger problem, off_t is usually 8 bytes and the built-in  dl 
> can only handle 4 byte types.  (Or, if it can handle 8 byte types,  I 
> couldn't figure out how.)

good pickup.
I would expect the higher-order word to be 0 in 99% of cases.
You could treat an 8-byte off_t field as two separate unsigned longs and
extract the two longs separately and then add them together
if the higher-order word is indeed anything but 0.