Annotation of libwww/Library/src/HTEvent.html, revision 2.7.2.4
2.1 eric 1: <HTML>
2: <HEAD>
2.4 frystyk 3: <TITLE>W3C Reference Library libwww Event Class</TITLE>
2.1 eric 4: </HEAD>
5: <BODY>
2.4 frystyk 6: <H1>
7: The Event Class
2.3 frystyk 8: </H1>
2.1 eric 9: <PRE>
10: /*
11: ** (c) COPYRIGHT MIT 1995.
12: ** Please first read the full copyright statement in the file COPYRIGH.
13: */
2.4 frystyk 14: </PRE>
15: <P>
16: The Event Class defines any event manager to be used by libwww for handling
17: events. An <I>event</I> is not strictly defined as it is highly platform
18: dependent and hence out of scope for the Library. If you are using the libwww
19: pseudo threads on Unix then an event is when the <I>select()</I> system
20: call returns a notification on a socket descriptor, but it may as well
21: be an asynchronous event from the windows manager etc. If your application
22: is not using anything but traditional blocking sockets then you do not need
23: an event manager at all. In that case, libwww will block on any socket or
24: system call until the process can proceed.
25: <P>
26: The libwww interface to an event manager is very simple as it consists of
27: <B>registering</B> a <I>socket descriptor</I>, the <I>location</I> in the
28: program, and the <I>current state</I> when an operation (for example
29: <CODE>read</CODE>) would block. When the event manager at a later point in
30: time gets a notification that the socket has become ready, it can then call
31: libwww with the state saved from the registration and libwww can continue.
32: Second, libwww must be able to <B>unregister</B> a socket when it is not
33: anymore in a state where it can block. <I>Only</I> in case the application
34: wishes to use <I>non-blocking</I> sockets it should register methods for
35: handling the <B>registration</B> process as described below.
36: <P>
37: <B>Note</B>: The library <B>core</B> does <I>not</I> define any event manager
38: - it is considered part of the application. The library comes with a
39: <A HREF="HTEvntrg.html">default event manager</A> which can be initiated
2.6 frystyk 40: using the function <CODE>HTEventInit()</CODE> in <A HREF="HTInit.html">HTInit
41: module</A>
2.4 frystyk 42: <P>
43: This module is implemented by <A HREF="HTEvent.c">HTEvent.c</A>, and it is
44: a part of the <A HREF="http://www.w3.org/pub/WWW/Library/">W3C Reference
45: Library</A>.
46: <PRE>
2.1 eric 47: #ifndef HTEVENT_H
48: #define HTEVENT_H
2.2 frystyk 49: #include "sysdep.h"
50:
2.7.2.4 ! eric 51: #if 0
2.4 frystyk 52: #define FD_NONE 0
53: #define FD_ALL (FD_READ | FD_WRITE | FD_OOB | FD_ACCEPT | FD_CONNECT |FD_CLOSE)
54: #define FD_UNREGISTER (((FD_ALL) << 1) & (~(FD_ALL)))
2.7.2.4 ! eric 55: #endif
2.4 frystyk 56:
2.2 frystyk 57: typedef enum _HTPriority {
58: HT_PRIORITY_INV = -1,
59: HT_PRIORITY_OFF = 0,
60: HT_PRIORITY_MIN = 1,
61: HT_PRIORITY_MAX = 20
62: } HTPriority;
63:
2.7.2.1 eric 64: typedef enum {
2.7.2.3 frystyk 65: HTEvent_BEGIN = 0,
66: HTEvent_READ = 0x001,
67: HTEvent_ACCEPT = 0x002,
68: HTEvent_CLOSE = 0x004,
69: HTEvent_WRITE = 0x108,
70: HTEvent_CONNECT = 0x110,
71: HTEvent_OOB = 0x220,
72: HTEvent_END = 0x080,
73: HTEvent_ALL = 0xff,
74: HTEvent_TYPES = 3
75: } HTEventType;
76:
2.7.2.1 eric 77: #define HTEvent_BITS(type) (type & 0xff)
78: #define HTEvent_INDEX(type) (type >> 8)
2.1 eric 79:
2.7.2.1 eric 80: /* Avoid circular include for HTReq->HTNet->HTHost: HTEvent blah */
81: typedef struct _HTEvent HTEvent;
2.1 eric 82: #include "HTReq.h"
83: </PRE>
2.3 frystyk 84: <H2>
2.7 eric 85: <A NAME="eventHandlers">Event Handlers</A>
2.3 frystyk 86: </H2>
87: <P>
2.4 frystyk 88: A <I>location</I> is a function that can be registered by the event manager
89: and called at a later point in time in order to continue an operation. All
90: locations must be of type <CODE>HTEventCallback</CODE> as defined here:
2.2 frystyk 91: <PRE>
2.7.2.2 eric 92: typedef int HTEventCallback (SOCKET, void *, HTEventType);
2.7.2.1 eric 93:
94: struct _HTEvent {
95: HTPriority priority; /* Priority of this request (event) */
96: HTEventCallback * cbf; /* Protocol state machine */
97: void * param; /* HTEvent_register parameter */
98: HTRequest * request;
99: };
2.2 frystyk 100: </PRE>
2.4 frystyk 101: <P>
102: There are many default event handlers provided with the Library. For example,
103: all the protocol modules such as the <A HREF="HTTP.html">HTTP client module</A>
104: are implemented as event handlers. In stead of using blocking sockets, this
105: allows a protocol module to register itself when performing an operation
106: that would block. When the sockets becomes ready the handler is called with
107: th socket in question, the request object, and the socket operation
2.3 frystyk 108: <H2>
2.4 frystyk 109: Registering and Unregistering Event Handlers
2.3 frystyk 110: </H2>
111: <P>
2.4 frystyk 112: As mentioned above, the only interface libwww requires from an event manager
113: is a method to <I>register</I> an event handler when an operation would block
114: and <I>unregister</I> it when the operation has completed The library registers
115: and unregisters event handlers by calling the following two functions:
2.7.2.1 eric 116: <PRE>
2.7.2.2 eric 117: extern int HTEvent_register (SOCKET, HTEventType, HTEvent *);
118: extern int HTEvent_unregister (SOCKET, HTEventType);
2.4 frystyk 119: </PRE>
120: <P>
121: The register function contains information about which socket we are waiting
122: on to get ready and which operation we are waiting for (read, write, etc.),
123: the request object containing the current request, the event handler that
124: we want to be called when the socket becomes reasy, and finally the priority
125: by which we want the thread to be processed by the event manager. Likewise,
126: libwww can unregister a operation on a socket which means that libwww is
127: no longer waiting for this actiion to become ready.
128: <H2>
129: Registering an Event Manager
130: </H2>
131: <P>
132: The Library core does not contain any event manager as it depends on whether
133: you want to use pseudo threads no threads, or real threads. Instead, libwww
134: comes with a <A HREF="HTEvntrg.html">default implementation</A> that you
135: may register, but you may as well implement and register your own. The register
136: and unregister functions above actually does nothing than looking for a
137: registered event manager and then passes the call on to that. You register
138: your own event manager by using the methods below:
2.1 eric 139: <PRE>
2.7.2.2 eric 140: typedef int HTEvent_registerCallback(SOCKET, HTEventType, HTEvent *);
141: typedef int HTEvent_unregisterCallback(SOCKET, HTEventType);
2.1 eric 142:
143: extern void HTEvent_setRegisterCallback(HTEvent_registerCallback *);
144: extern void HTEvent_setUnregisterCallback(HTEvent_unregisterCallback *);
2.7.2.1 eric 145: extern BOOL HTEvent_setCallback(HTEvent * event, HTEventCallback * cbf);
146: extern BOOL HTEvent_setParam(HTEvent * event, void * param);
147: extern BOOL HTEvent_setPriority(HTEvent * event, HTPriority priority);
2.1 eric 148: </PRE>
2.3 frystyk 149: <P>
2.4 frystyk 150: You can register the event manager provided together with libwww by using
2.6 frystyk 151: the <CODE>HTEventInit()</CODE> in the <A HREF="HTInit.html">HTInit module</A>
2.1 eric 152: <PRE>
153: #endif /* HTEVENT_H */
154: </PRE>
2.3 frystyk 155: <P>
156: <HR>
2.1 eric 157: <ADDRESS>
2.7.2.4 ! eric 158: @(#) $Id: HTEvent.html,v 2.7.2.3 1996/11/06 00:38:35 frystyk Exp $
2.1 eric 159: </ADDRESS>
2.3 frystyk 160: </BODY></HTML>
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