Re: Syntax question...

[Pierangelo Masarati <ando@sys-net.it>]

Armbrust, Daniel C. wrote:

> Howard recommended that I modify back-bdb/idl.h BDB_IDL_DB_SIZE and 
> BDB_IDL_UM_SIZE to work around a problem I reported (ITS #3343).
>
> Those lines of code are:
>
> /* IDL sizes - likely should be even bigger
> *   limiting factors: sizeof(ID), thread stack size
> */
> #define BDB_IDL_DB_SIZE         (1<<16) /* 64K IDL on disk */
> #define BDB_IDL_UM_SIZE         (1<<17) /* 128K IDL in memory */
>
>
> This is probably something I should know - but what numbers would I put in here if I wanted to quadruple each of these variable values?  I don't understand the syntax of (1<<16) (and haven't been able to find any documentation)
>  
That's the (left) shift operator; it means: "take the left operand (1) 
and shift it leftwise (towards higher values) as many bits as indicated 
by the right operand.  I think Howard used that to make it clear what 
power of 2 he was using :)  You can read it as 2^16 and 2^17 
respectively, so to quadruple them you may use (1<<20) and (1<<21).

p.




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