I/O Stream Class Definition

/*
**	(c) COPYRIGHT MIT 1995.
**	Please first read the full copyright statement in the file COPYRIGH.
*/
A stream object is something which accepts a stream of text. Generally streams are cascaded into stream pipes where the output of a stream is directed into the input of the down stream object. The input and output streams differs from other streams in that they are used to communicate directly with a transport.

This module is a part of the W3C Reference Library.

All methods in the stream definition return an integer. The general return codes from the methods are:

As streams now have a return value, it is very important that these return values are passed upstream to all the other streams in the stream pipe. 

#ifndef HTIOSTREAM_H
#define HTIOSTREAM_H

typedef struct _HTInputStream HTInputStream;
typedef struct _HTOutputStream HTOutputStream;

#include "HTList.h"
#include "HTStream.h"
#include "HTChannl.h"
#include "HTNet.h"

Input Stream

An input stream is a stream that can read data from a transport and via a channel putting the data down to the application. 

typedef struct _HTInputStreamClass {

    char * name;
This field is for diagnostics only 
    int (*flush)	(HTInputStream * me);
The flush method is introduced in order to allow the stream to put any buffered data down the stream pipe but without taking the stream pipe down. It is for the stream to decide whether it has buffered data or not. In some situations, the stream might not want to send buffered data down the target as the date might be relevant for this stream only. 
    int (*_free)	(HTInputStream * me);
The free method is like the flush method but it also frees the current stream object and all stream objects down stream. When the free method has been called, the whole stream pipe (not only this object) should not accept any more data. See also the close method below 
    int (*abort)	(HTInputStream * me, HTList * errorlist);
The abort method should only be used if a stream is interrupted, for example by the user, or an error occurs. 
    int (*read)		(HTInputStream * me);
The read method is the method by which we can read data from the transport layer. 
    int (*close)	(HTInputStream * me);
The close method closes the transport and deletes the input stream object. Note that this is different than the free method which doesn't have to delete the input stream object itself. 
} HTInputStreamClass;

Output Stream

The output stream is similar to the generic stream definition in that it has a superset of methods. The param parameter and the mode parameter can be used for whatever purpose suited. 
typedef struct _HTOutputStreamClass {

    char * name;

    int (*flush)	(HTOutputStream * me);

    int (*_free)	(HTOutputStream * me);

    int (*abort)	(HTOutputStream * me, HTList * errorlist);

    int (*put_character)(HTOutputStream * me, char ch);

    int (*put_string)	(HTOutputStream * me, const char * str);

    int (*put_block)	(HTOutputStream * me, const char * str, int len);
See the Generic Stream Definition for an explanation of these methods. Note that they all have a HTOutputStream object a the parameter, not a generic stream. This is to avoid incompatible pointer warnings 
    int (*close)	(HTOutputStream * me);
The close method closes the transport and deletes the input stream object. Note that this is different than the free method which doesn't have to delete the input stream object itself. 
} HTOutputStreamClass;

Transport Streams

Transport streams are special streams with creation methods like defined below. Transport streams can be registered in the HTTransport module as ways of communicating with the a transport.

Transport Input Stream

We have two modes of the input stream depending on model used for data reading is PUSH or PULL. The PUSH model is suitable if we are using pseudo threads based on a select() call or equivalent and the PULL is suitable in a real thread environment. In the latter case it doesn't matter if a read procedure blocks as this only concerns a single thread. 
typedef HTInputStream * HTInput_new	(HTNet *	net,
					 HTChannel *	ch,
					 HTStream *	target,
					 void *		param,
					 int		mode);

Transport Output Stream

typedef HTOutputStream * HTOutput_new	(HTNet *	net,
					 HTChannel *	ch,
					 void *		param,
					 int		mode);

#endif /* HTIOSTREAM_H */
@(#) $Id: HTIOStream.html,v 2.1 1996/04/12 17:47:20 frystyk Exp $