Re: [boost] [log] Comments

Subject: Re: [boost] [log] Comments
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2010-03-15 18:34:52

On 03/15/2010 11:47 PM, Steven Watanabe wrote:
> AMDG
>
> Vladimir Prus wrote:
>> There's another thing about component/severity logging that I have
>> apparently
>> forgot about -- filtering. It is surely necessary to change filtered
>> components
>> dynamically -- either while the application is running, or between
>> runs, therefore
>> lambda expression that compares to a fixed string will not be enough
>> -- we need
>> a lookup in a map. It's not obvious to me how to form a lambda expression
>> to do a lookup in a map using the library, e.g. something like:
>>
>> enabled_components.count(attr<string>("Component"))
>>
>> So I wonder:
>>
>> 1. What is the actual syntax to do this inside lambda expression.
>
> There is no simple syntax for it. (The lambda functionality is
> rather crippled compared to a real lambda library.) You
> could probably do it with boost::bind and the satisfies function.
> Also, this by itself would be dangerous, since filters need to
> be thread safe.

In my view, the filter should be replaced on update. You can have the 
map of components or whatever, and the filter pointing to them. On 
update you create a new map and a new filter, and set it to the 
core/sinks. No additional locking required, no special syntax, 
everything's safe and clean. Same goes for formatters.