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IConduitFilter Struct Reference

Inheritance diagram for IConduitFilter:

Conduit ConduitFilter DeviceConduit Socket EndianFilter Console::ConsoleConduit Console::ConsoleConduit FileConduit DatagramSocket ServerSocket SocketConduit EndianFilter16 EndianFilter32 List of all members.

Public Member Functions

uint reader (void[] dst)
uint writer (void[] dst)
void bind (IConduit conduit, IConduitFilter next)
void unbind ()

Detailed Description

Define a conduit filter base-class. The filter is invoked via its reader() method whenever a block of content is being read, and by its writer() method whenever content is being written.

The filter should return the number of bytes it has actually produced: less than or equal to the length of the provided array.

Filters are chained together such that the last filter added is the first one invoked. It is the responsibility of each filter to invoke the next link in the chain; for example:

        class MungingFilter : ConduitFilter
        {
                int reader (void[] dst)
                {
                        // read the next X bytes
                        int count = next.reader (dst);

                        // set everything to '*' !
                        dst[0..count] = '*';

                        // say how many we read
                        return count;
                }

                int writer (void[] src)
                {
                        byte[] tmp = new byte[src.length];

                        // set everything to '*'
                        tmp = '*';

                        // write the munged output
                        return next.writer (tmp);
                }
        }

Notice how this filter invokes the 'next' instance before munging the content ... the far end of the chain is where the original IConduit reader is attached, so it will get invoked eventually assuming each filter invokes 'next'. If the next reader fails it will return IConduit.Eof, as should your filter (or throw an IOException). From a client perspective, filters are attached like this:

        FileConduit fc = new FileConduit (...);

        fc.attach (new ZipFilter);
        fc.attach (new MungingFilter);

Again, the last filter attached is the first one invoked when a block of content is actually read. Each filter has two additional methods that it may use to control behavior:

        class ConduitFilter : IConduitFilter
        {
                protected IConduitFilter next;

                void bind (IConduit conduit, IConduitFilter next)
                {
                        this.next = next;
                }

                void unbind ()
                {
                }
        }

The first method is invoked when the filter is attached to a conduit, while the second is invoked just before the conduit is closed. Both of these may be overridden by the filter for whatever purpose desired.

Note that a conduit filter can choose to sidestep reading from the conduit (per the usual case), and produce its input from somewhere else entirely. This mechanism supports the notion of 'piping' between multiple conduits, or between a conduit and something else entirely; it's a bridging mechanism.

Definition at line 249 of file IConduit.d.


Member Function Documentation

uint reader void[]  dst  ) 
 

filter-specific reader

Reimplemented in Conduit, ConduitFilter, EndianFilter, and Socket.

Referenced by Conduit::read(), EndianFilter::reader(), and ConduitFilter::reader().

uint writer void[]  dst  ) 
 

filter-specific writer

Reimplemented in Conduit, ConduitFilter, EndianFilter, and Socket.

Referenced by Conduit::write(), EndianFilter::writer(), and ConduitFilter::writer().

void bind IConduit  conduit,
IConduitFilter  next
 

Reimplemented in Conduit, and ConduitFilter.

Referenced by Conduit::attach().

void unbind  ) 
 

Reimplemented in Conduit, and ConduitFilter.

Referenced by Conduit::close(), and ConduitFilter::unbind().


The documentation for this struct was generated from the following file:
Generated on Sat Dec 24 17:28:39 2005 for Mango by  doxygen 1.4.0