Re: Streams filter API

On 2002-08-20 22:47:51, Wez Furlong wrote: > I've just comitted the streams filter API to CVS. Looks really nice. I just wanted to start and try to write an example for me, but then I wondered about following: > The concept is that a series of filters can be applied to a given > stream instance (as a doubly-linked-list); writing to the stream > causes the buffer to pass through the filters from head to tail, > before finally being written to the underlying stream. [...] > Likewise, reading from the stream also causes the data to pass > through the filters, but in the reverse order. Is there some easy way to restrict a filter to work only in one direction? Say I want a filter, which only can be used to read data, but not to write. Or a filter which is used for both ways, but not both at the same time, so that you get the information at create time, if this filter will be used for reading or for writing. I think this will make it much easier to write e.g. compression or crypto filters, because reading and writing to the same compressed stream often is hard to achieve. I think this may be one reason, that Java has different Input-/OutputStreams. If you know the direction at create time, you can make your read or write initializations and then only support this methods, otherwise you would have to delay the initialization and make complex checks, that you don't read from a stream you have started writing to or similar. What do you think? Stefan PS: It would be really cool, if you could implement your own filters in PHP. Maybe you have to provide a PHP function which gets a string as paramter and returns another? Would that be possible? -- Stefan Röhrich stefan@roehri.ch, sr@linux.de http://www.roehri.ch/~sr/