From: Lloyd Zusman <ljz@...>
Date: 2004-10-12T03:16:09+09:00
Subject: Re: Forcing DBM.open to be read-only?

Mauricio Fern�ndez <batsman.geo@yahoo.com> writes:

> On Tue, Oct 12, 2004 at 02:26:10AM +0900, Lloyd Zusman wrote:
>> I'd like to use the DBM routines in ruby, and I want to force DBM.open
>> to be performed in read-only mode.  However, looking at the source code
>> (in ext/dbm/dbm.c), it looks like ruby always tries to open the database
>> in read-write mode before trying it in read-only mode [see the
>> fdbm_initialize() routine, below].
>> 
>> Am I misinterpreting something?
>> 
>> In any case, how can I do a DBM.open with the guarantee that it will
>> never even try to open the file in read-write mode?
>
> maybe  DBM.open(filename, 0666, DBM::READER) ? 
> (that sets the RUBY_DBM_RW_BIT... )

That logic is a little confusing to me: by _setting_ RUBY_DBM_RW_BIT in
the flags that are passed to DBM.open, that causes the bit to get
_cleared_ before the dbm_open call gets made.  That seems
counter-intuitive, but as long as it works, I'm not going to
complain. :)

Thanks.


>>       if (rb_scan_args(argc, argv, "12", &file, &vmode, &vflags) == 1) {
>>           mode = 0666;            /* default value */
>>       }
> [...]   
>>       if (flags & RUBY_DBM_RW_BIT) {
>>           flags &= ~RUBY_DBM_RW_BIT;
>>           dbm = dbm_open(RSTRING(file)->ptr, flags, mode);
>>       }

-- 
 Lloyd Zusman
 ljz@asfast.com
 God bless you.