hthost.h

www工具包. 这是W3C官方支持的www支撑库. 其中提供通用目的的客户端的WebAPI: complete HTTP/1.1 (with caching, pipelining, PUT, POS

/*

  					W3C Sample Code Library libwww Host Class


!
  The Host Class
!
*/

/*
**	(c) COPYRIGHT MIT 1995.
**	Please first read the full copyright statement in the file COPYRIGH.
*/

/*

The Host class manages what we know about a remote host. This can for example
be what type of host it is, and what version it is using. Notice that a host
object can be used to describe both a server or a client - all information
in the Host object can be shared regardless of whether it is to be used in
a server application or a client application.

This module is implemented by HTHost.c, and it is
a part of the  W3C Sample Code
Library.
*/

#ifndef HTHOST_H
#define HTHOST_H

typedef struct _HTHost HTHost;
#define HOST_HASH_SIZE		HT_M_HASH_SIZE

#include "HTChannl.h"
#include "HTReq.h"
#include "HTEvent.h"
#include "HTProt.h"
#include "HTTimer.h"

/*

The Host class contains information about the remote host, for example the
type (HTTP/1.0, HTTP/1.1, FTP etc.) along with information on how the connections
can be used (if it supports persistent connections, interleaved access etc.)
.
  Creation and Deletion Methods
.

We keep a cache of information that we know about a remote host. This allows
us to be much more detailed in generating requests. Search the host info
cache for a host object or create a new one and add it. Examples of host
names are
	 
	   o 
	     www.w3.org
	   o 
	     www.foo.com:8000
	 
	 (
  Add a Host Object
)
*/

extern HTHost * HTHost_new (char * host, u_short u_port);
extern HTHost * HTHost_newWParse(HTRequest * request, char * url, u_short u_port);
extern int HTHost_hash (HTHost * host);

/*
(
  Delete a Host Object
)

The Host Class contains an automatic garbage collection of Host objects so
that we don't keep information around that is stale.
(
  Find a Host Object
)

Searches the cache of known hosts to see if we already have information about
this host. If not then we return NULL.
*/

extern HTHost * HTHost_find (char * host);

/*
(
  Delete the Host table
)

Cleanup and delete the host table.
*/

extern void HTHost_deleteAll (void);

/*
(
  Is Host Idle?
)

You can use this function to see whether a host object is idle or in use.
We have several modes describing how and when a host is idle. This is a function
of the Transport Object
*/

extern BOOL HTHost_isIdle (HTHost * host);

/*
.
  Remote Host Information
.

We keep track of the capabilities of the host in the other end so thatwe
may adjust our queries to fit it better
(
  Remote Host Name
)

Get the name of the remote host. This is set automatically when a new Host
object and can be asked for at any point in time. You can not change the
host name but must create a new Host object instead.
*/

extern char * HTHost_name	(HTHost * host);

/*
(
  Remote Host Protocol Class and Version
)

Define the host class of the host at the other end. A class is a
generic description of the protocol which is exactly like the access method
in a URL, for example "http" etc. The host version is a finer
distinction (sub-class) between various versions of the host class, for example
HTTP/0.9, HTTP/1.1 etc. The host version is a bit flag that the protocol
module can define on its own. That way we don't have to change this module
when registering a new protocol module. The host type is a description
of whether we can keep the connection persistent or not.
*/

extern char * HTHost_class	(HTHost * host);
extern void HTHost_setClass	(HTHost * host, char * s_class);

extern int  HTHost_version	(HTHost * host);
extern void HTHost_setVersion	(HTHost * host, int version);

/*
(
  Public Methods accessible on This Host
)

A server can inform a client about the supported methods using the
Public header.
*/
extern HTMethod HTHost_publicMethods 	(HTHost * me);
extern void HTHost_setPublicMethods 	(HTHost * me, HTMethod methodset);
extern void HTHost_appendPublicMethods	(HTHost * me, HTMethod methodset);

/*
(
  Server Name of Remote Host
)

A server can send its server application name and version in a HTTP response.
We pick up this information and add it to the Host object
*/
extern char * HTHost_server	(HTHost * host);
extern BOOL HTHost_setServer	(HTHost * host, const char * server);

/*
(
  User Agent Name of Remote Host
)

A client can send the name of the client application in a HTTP request. We
pick up this information and add it to the Host Object
*/
extern char * HTHost_userAgent 	(HTHost * host);
extern BOOL HTHost_setUserAgent	(HTHost * host, const char * userAgent);

/*
(
  Range Units Accepted by this Host
)

Since all HTTP entities are represented in HTTP messages as sequences of
bytes, the concept of a byte range is meaningful for any HTTP entity. (However,
not all clients and servers need to support byte-range operations.) Byte
range specifications in HTTP apply to the sequence of bytes in the entity-body
(not necessarily the same as the message-body). A byte range operation may
specify a single range of bytes, or a set of ranges within a single entity.

You can also check whether a specific range unit is OK. We always say
YES except if we have a specific statement from the server that
it doesn't understand byte ranges - that is - it has sent "none" in a
"Accept-Range" response header
*/

extern char * HTHost_rangeUnits  (HTHost * host);
extern BOOL HTHost_setRangeUnits (HTHost * host, const char * units);
extern BOOL HTHost_isRangeUnitAcceptable (HTHost * host, const char * unit);

/*
(
  User Defined Contexts
)

This can be used for anything that the application would like to keep tabs
on.
*/

extern void HTHost_setContext (HTHost * me, void * context);
extern void * HTHost_context  (HTHost * me);

/*
.
  Register a Request on a Host Object
.

Requests are queued in the Host object until we have
resources to start them. The request is in the form
of a Net object as we may have multiple socket requests
per Request object. This is for example the case
with FTP which uses two connections.
*/

extern int  HTHost_addNet    (HTHost * host, HTNet * net);
extern BOOL HTHost_deleteNet (HTHost * host, HTNet * net, int status);

extern HTList * HTHost_net   (HTHost * host);

/*
.
  Channels
.

A Channel object is an abstraction for a transport,
like a TCP connection, for example. Each host object can have at most one
channel object associated with it.
(
  Create a Channel to a Host
)

As a Net Object doesn't necessarily know whether
there is a channel up and running and whether that channel can be reused,
it must do an explicit connect the the host.
*/

extern int HTHost_connect (HTHost * host, HTNet * net, char * url);

extern int HTHost_accept  (HTHost * host, HTNet * net, char * url);

extern int HTHost_listen  (HTHost * host, HTNet * net, char * url);

/*
(
  Is Channel About to Close?
)

As soon as we know that a channel is about to close (for example because
the server sends us a Connection: close header field) then we register
this informtation in the Host object:
*/

extern BOOL HTHost_setCloseNotification (HTHost * host, BOOL mode);
extern BOOL HTHost_closeNotification (HTHost * host);

/*
(
  Find Channel Associated with a Host Object
)

Here you can find an already associated channel with a host object or you
can explicitly associate a channel with a host object.
*/

extern BOOL HTHost_setChannel (HTHost * host, HTChannel * channel);
extern HTChannel * HTHost_channel (HTHost * host);

/*
(
  Delete a Channel
)

When a channel is deleted, it must be unregistered from the host object which
is done by this operation:
*/

extern BOOL HTHost_clearChannel (HTHost * host, int status);

/*
.
  Transport Mode
.

The way a channel can be used depends on the
transport and what mode the channel is in. The
mode (whether we can use persistent connections, pipeline, etc.) may change
mode in the middle of a connection If the new mode is lower than the old
mode then adjust the pipeline accordingly. That is, if we are going into
single mode then move all entries in the pipeline and move the rest to the
pending queue. They will get launched at a later point in time.
*/

extern HTTransportMode HTHost_mode (HTHost * host, BOOL * active);
extern BOOL HTHost_setMode (HTHost * host, HTTransportMode mode);

/*
.
  Handling Pending Requests
.

There are two ways we can end up with pending requests:

  o 
	     If we are out of sockets then register new host objects as pending.
	   o 
	     If we are pending on a connection then register new net objects as pending
	 

This set of functions handles pending host objects and can start new requests
as resources get available. The first function checks the host object for