Annotation of libwww/Library/src/HTHost.html, revision 2.15
2.1 frystyk 1: <HTML>
2: <HEAD>
2.4 frystyk 3: <!-- Changed by: Henrik Frystyk Nielsen, 2-Jul-1996 -->
2.14 frystyk 4: <TITLE>W3C Sample Code Library libwww Host Class</TITLE>
2.1 frystyk 5: </HEAD>
6: <BODY>
2.3 frystyk 7: <H1>
8: The Host Class
9: </H1>
2.1 frystyk 10: <PRE>
11: /*
12: ** (c) COPYRIGHT MIT 1995.
13: ** Please first read the full copyright statement in the file COPYRIGH.
14: */
15: </PRE>
2.3 frystyk 16: <P>
17: The Host class manages what we know about a remote host. This can for example
18: be what type of host it is, and what version it is using. Notice that a host
19: object can be used to describe both a server or a client - all information
20: in the Host object can be shared regardless of whether it is to be used in
21: a server application or a client application.
22: <P>
23: This module is implemented by <A HREF="HTHost.c">HTHost.c</A>, and it is
2.14 frystyk 24: a part of the <A HREF="http://www.w3.org/pub/WWW/Library/"> W3C Sample Code
2.3 frystyk 25: Library</A>.
2.1 frystyk 26: <PRE>
27: #ifndef HTHOST_H
28: #define HTHOST_H
29:
30: typedef struct _HTHost HTHost;
2.8 frystyk 31: #define HOST_HASH_SIZE 67
2.1 frystyk 32:
33: #include "HTChannl.h"
34: #include "HTReq.h"
2.2 frystyk 35: #include "HTEvent.h"
2.8 frystyk 36: #include "HTProt.h"
2.15 ! frystyk 37: #include "HTTimer.h"
2.1 frystyk 38: </PRE>
2.3 frystyk 39: <P>
40: The Host class contains information about the remote host, for example the
41: type (HTTP/1.0, HTTP/1.1, FTP etc.) along with information on how the connections
42: can be used (if it supports persistent connections, interleaved access etc.)
43: <H2>
44: Creation and Deletion Methods
45: </H2>
46: <P>
47: We keep a cache of information that we know about a remote host. This allows
2.5 frystyk 48: us to be much more detailed in generating requests. Search the host info
49: cache for a host object or create a new one and add it. Examples of host
50: names are
2.1 frystyk 51: <UL>
2.3 frystyk 52: <LI>
53: www.w3.org
54: <LI>
55: www.foo.com:8000
2.1 frystyk 56: </UL>
2.3 frystyk 57: <H3>
58: Add a Host Object
59: </H3>
2.1 frystyk 60: <PRE>
2.10 eric 61: extern HTHost * HTHost_new (char * host, u_short u_port);
62: extern HTHost * HTHost_newWParse(HTRequest * request, char * url, u_short u_port);
2.8 frystyk 63: extern int HTHost_hash (HTHost * host);
2.1 frystyk 64: </PRE>
2.3 frystyk 65: <H3>
66: Delete a Host Object
67: </H3>
68: <P>
69: The Host Class contains an automatic garbage collection of Host objects so
70: that we don't keep information around that is stale.
2.6 frystyk 71: <H3>
72: Find a Host Object
73: </H3>
74: <P>
75: Searches the cache of known hosts to see if we already have information about
76: this host. If not then we return NULL.
77: <PRE>extern HTHost * HTHost_find (char * host);
78: </PRE>
2.3 frystyk 79: <H2>
2.12 frystyk 80: Remote Host Information
2.3 frystyk 81: </H2>
82: <P>
2.12 frystyk 83: We keep track of the capabilities of the host in the other end so thatwe
84: may adjust our queries to fit it better
2.3 frystyk 85: <H3>
2.5 frystyk 86: Remote Host Name
87: </H3>
88: <P>
89: Get the name of the remote host. This is set automatically when a new Host
90: object and can be asked for at any point in time. You can not change the
91: host name but must create a new Host object instead.
92: <PRE>
93: extern char * HTHost_name (HTHost * host);
94: </PRE>
95: <H3>
96: Remote Host Protocol Class and Version
2.3 frystyk 97: </H3>
98: <P>
99: Define the <EM>host class</EM> of the host at the other end. A class is a
100: generic description of the protocol which is exactly like the access method
101: in a URL, for example "http" etc. The <EM>host version</EM> is a finer
102: distinction (sub-class) between various versions of the host class, for example
103: HTTP/0.9, HTTP/1.1 etc. The host version is a bit flag that the protocol
104: module can define on its own. That way we don't have to change this module
105: when registering a new protocol module. The <EM>host type</EM> is a description
106: of whether we can keep the connection persistent or not.
2.1 frystyk 107: <PRE>
108: extern char * HTHost_class (HTHost * host);
109: extern void HTHost_setClass (HTHost * host, char * s_class);
110:
111: extern int HTHost_version (HTHost * host);
112: extern void HTHost_setVersion (HTHost * host, int version);
113: </PRE>
2.3 frystyk 114: <H3>
2.12 frystyk 115: Public Methods accessible on This Host
2.4 frystyk 116: </H3>
117: <P>
118: A server can inform a client about the supported methods using the
119: <CODE>Public</CODE> header.
120: <PRE>extern HTMethod HTHost_publicMethods (HTHost * me);
121: extern void HTHost_setPublicMethods (HTHost * me, HTMethod methodset);
122: extern void HTHost_appendPublicMethods (HTHost * me, HTMethod methodset);
123: </PRE>
2.12 frystyk 124: <H3>
2.4 frystyk 125: Server Name of Remote Host
2.12 frystyk 126: </H3>
2.4 frystyk 127: <P>
128: A server can send its server application name and version in a HTTP response.
129: We pick up this information and add it to the Host object
130: <PRE>extern char * HTHost_server (HTHost * host);
131: extern BOOL HTHost_setServer (HTHost * host, const char * server);
132: </PRE>
2.12 frystyk 133: <H3>
2.4 frystyk 134: User Agent Name of Remote Host
2.12 frystyk 135: </H3>
2.4 frystyk 136: <P>
137: A client can send the name of the client application in a HTTP request. We
2.5 frystyk 138: pick up this information and add it to the Host Object
2.4 frystyk 139: <PRE>extern char * HTHost_userAgent (HTHost * host);
140: extern BOOL HTHost_setUserAgent (HTHost * host, const char * userAgent);
141: </PRE>
2.12 frystyk 142: <H3>
2.7 frystyk 143: Range Units Accepted by this Host
2.12 frystyk 144: </H3>
2.7 frystyk 145: <P>
146: Since all HTTP entities are represented in HTTP messages as sequences of
147: bytes, the concept of a byte range is meaningful for any HTTP entity. (However,
148: not all clients and servers need to support byte-range operations.) Byte
149: range specifications in HTTP apply to the sequence of bytes in the entity-body
150: (not necessarily the same as the message-body). A byte range operation may
151: specify a single range of bytes, or a set of ranges within a single entity.
152: <P>
153: You can also check whether a specific range unit is OK. We always say
154: <CODE>YES</CODE> except if we have a specific statement from the server that
155: it doesn't understand byte ranges - that is - it has sent "none" in a
156: "Accept-Range" response header
157: <PRE>
158: extern char * HTHost_rangeUnits (HTHost * host);
159: extern BOOL HTHost_setRangeUnits (HTHost * host, const char * units);
160: extern BOOL HTHost_isRangeUnitAcceptable (HTHost * host, const char * unit);
161: </PRE>
2.12 frystyk 162: <H2>
163: Persistent Connections
164: </H2>
2.3 frystyk 165: <P>
166: We don't want more than MaxSockets-2 connections to be persistent in order
167: to avoid deadlock.
2.1 frystyk 168: <PRE>
2.8 frystyk 169: extern BOOL HTHost_setPersistent (HTHost * host, BOOL persistent,
170: HTTransportMode mode);
2.5 frystyk 171: extern BOOL HTHost_clearChannel (HTHost * host, int status);
2.1 frystyk 172:
173: extern HTChannel * HTHost_channel (HTHost * host);
174: </PRE>
2.3 frystyk 175: <H3>
176: Is this host Persistent?
177: </H3>
178: <P>
2.1 frystyk 179: Check whether we have a persistent channel or not
180: <PRE>
181: extern BOOL HTHost_isPersistent (HTHost * host);
2.15 ! frystyk 182: extern BOOL HTHost_setCloseNotification (HTHost * host, BOOL mode);
! 183: extern BOOL HTHost_closeNotification (HTHost * host);
2.1 frystyk 184: </PRE>
2.3 frystyk 185: <H3>
186: Timing Persistent Channels
187: </H3>
188: <P>
189: Normally we wait for the peer process to close persistent connections but
190: in order not to use up our own resources, we have a timeout on our own. The
191: default value is 1 hour, but you can modify the value using the following
192: methods:
2.1 frystyk 193: <PRE>
194: extern time_t HTHost_persistTimeout (time_t timeout);
195: extern void HTHost_setPersistTimeout (time_t timeout);
196: </PRE>
2.3 frystyk 197: <P>
198: Each persistent connection has an absolute value of when this connection
199: most likely will expire. If the peer process does not inform us, we use our
200: own timeout.
2.1 frystyk 201: <PRE>
202: extern void HTHost_setPersistExpires (HTHost * host, time_t expires);
203: extern time_t HTHost_persistExpires (HTHost * host);
2.11 eric 204: extern void HTHost_setReqsPerConnection (HTHost * host, int reqs);
205: extern int HTHost_reqsPerConnection (HTHost * host);
206: extern void HTHost_setReqsMade (HTHost * host, int reqs);
207: extern int HTHost_reqsMade (HTHost * host);
2.1 frystyk 208: </PRE>
2.5 frystyk 209: <H2>
2.12 frystyk 210: Transport Mode
211: </H2>
212: <P>
213: Handle the connection mode. The mode may change mode in the middle of a
214: connection If the new mode is lower than the old mode then adjust the pipeline
215: accordingly. That is, if we are going into single mode then move all entries
216: in the pipeline and move the rest to the pending queue. They will get launched
217: at a later point in time.
218: <PRE>extern HTTransportMode HTHost_mode (HTHost * host, BOOL * active);
219: extern BOOL HTHost_setMode (HTHost * host, HTTransportMode mode);
220: </PRE>
221: <H2>
2.5 frystyk 222: Queuing Requests
223: </H2>
224: <P>
225: Requests are queued in the Host object until we have resources to start them.
226: The request is in the form of a Net object as we may have multiple socket
227: requests per <A HREF="HTReq.html">Request object</A>. This is for example
228: the case with <A HREF="WWWFTp.html">FTP</A> which uses two connections.
229: <PRE>extern int HTHost_addNet (HTHost * host, HTNet * net);
2.8 frystyk 230: extern BOOL HTHost_free (HTHost * host, int status);
2.5 frystyk 231: extern BOOL HTHost_deleteNet (HTHost * host, HTNet * net);
232: extern HTList * HTHost_net (HTHost * host);
233: </PRE>
234: <H3>
2.12 frystyk 235: Is the Host Idle?
2.5 frystyk 236: </H3>
237: <P>
238: Before we can start a new connection to the host we must be sure that the
239: host is idle. That is, if it can accept a new connection. We have several
240: modes describing how and when a host is idle. This is a function of the
241: <A HREF="HTTrans.html">Transport Object</A>
242: <PRE>extern BOOL HTHost_isIdle (HTHost * host);
243: </PRE>
2.3 frystyk 244: <H3>
2.5 frystyk 245: Handling Pending Requests
2.3 frystyk 246: </H3>
247: <P>
2.5 frystyk 248: There are two ways we can end up with pending reqyests:
249: <OL>
250: <LI>
251: If we are out of sockets then register new host objects as pending.
252: <LI>
253: If we are pending on a connection then register new net objects as pending
254: </OL>
255: <P>
256: This set of functions handles pending host objects and can start new requests
257: as resources get available. The first function checks the host object for
258: any pending <A HREF="HTNet.html">Net objects</A> and return the first of
259: these Net objects.
2.3 frystyk 260: <PRE>
2.5 frystyk 261: extern HTNet * HTHost_nextPendingNet (HTHost * host);
262: </PRE>
263: <P>
264: The second checks the list of pending host objects waiting for a socket and
265: returns the first of these Host objects.
266: <PRE>
267: extern HTHost * HTHost_nextPendingHost (void);
268: </PRE>
269: <P>
270: Start the next pending request if any. First we look for pending requests
271: for the same host and then we check for any other pending hosts. If nothing
272: pending then register a catch close event handler to have something catching
273: the socket if the remote server closes the connection, for example due to
274: timeout.
2.8 frystyk 275: <PRE>
276: extern BOOL HTHost_launchPending (HTHost * host);
277:
278: extern int HTHost_connect (HTHost * host, HTNet * net, char * url,
279: HTProtocolId port);
280: </PRE>
281: <P>
282: HTHost clients can use the host for all IO and take advantage of host
283: multiplexing and pipelining.
2.12 frystyk 284: <H2>
2.8 frystyk 285: Event Management
2.12 frystyk 286: </H2>
2.8 frystyk 287: <PRE>
288: extern int HTHost_register(HTHost * host, HTNet * net, HTEventType type);
289: extern int HTHost_unregister(HTHost * host, HTNet * net, HTEventType type);
290: extern int HTHost_tickleFirstNet(HTHost * host, HTEventType type);
291: extern BOOL HTHost_setRemainingRead(HTHost * host, size_t remainaing);
292: extern SockA * HTHost_getSockAddr(HTHost * host);
293: </PRE>
294: <H3>
2.12 frystyk 295: Control the Delayed Flush Timer
2.8 frystyk 296: </H3>
2.12 frystyk 297: <P>
298: These methods can control how long we want to wait for a flush on a given
299: host.
2.8 frystyk 300: <PRE>
2.12 frystyk 301: extern BOOL HTHost_setWriteDelay (HTHost * host, ms_t delay);
302: extern ms_t HTHost_writeDelay (HTHost * host);
303: extern int HTHost_findWriteDelay(HTHost * host, ms_t lastFlushTime, int buffSize);
2.8 frystyk 304: </PRE>
2.12 frystyk 305: <P>
306: It is also possible to explicitly require a flush using the following method
2.8 frystyk 307: <PRE>
2.12 frystyk 308: extern int HTHost_forceFlush(HTHost * host);
2.8 frystyk 309: </PRE>
2.12 frystyk 310: <P>
311: You can also set the global value so that all new host objects will inherit
312: this value instead of setting it individually.
313: <PRE>extern BOOL HTHost_setDefaultWriteDelay (ms_t delay);
314: extern ms_t HTHost_defaultWriteDelay (void);
315: </PRE>
2.8 frystyk 316: <H3>
2.12 frystyk 317: Event Timeouts
2.8 frystyk 318: </H3>
2.12 frystyk 319: <P>
320: Events can be assigned a timeout which causes the event to be triggered if
321: the timeout happens before other action is available on the socket. You can
322: assign a global timeout for all host object using the following methods
2.8 frystyk 323: <PRE>
2.12 frystyk 324: extern int HTHost_eventTimeout (void);
325: extern void HTHost_setEventTimeout (int millis);
2.8 frystyk 326: </PRE>
327: <H3>
2.12 frystyk 328: Get the Next Net object for Reading and Writing
2.8 frystyk 329: </H3>
330: <PRE>
331: extern HTNet * HTHost_firstNet (HTHost * host);
332: extern HTNet * HTHost_getReadNet (HTHost * host);
333: extern HTNet * HTHost_getWriteNet (HTHost * host);
334: </PRE>
335: <H3>
2.12 frystyk 336: Automatic Connection Recovery
337: </H3>
338: <P>
339: In case a pipeline is broken then we have to recover it and start again.
340: This is handled automatically by the host object
341: <PRE>extern BOOL HTHost_recoverPipe (HTHost * host);
342: </PRE>
343: <H3>
2.8 frystyk 344: Get input and output Streams for this Host
345: </H3>
346: <PRE>
347: extern HTInputStream * HTHost_getInput (HTHost * host, HTTransport * transport,
348: void * param, int mode);
349:
350: extern HTOutputStream * HTHost_getOutput (HTHost * host, HTTransport * tp,
351: void * param, int mode);
352: </PRE>
353: <H3>
2.12 frystyk 354: The Channel Associated with this Host
355: </H3>
356: <PRE>
357: extern BOOL HTHost_setChannel (HTHost * host, HTChannel * channel);
358: extern HTChannel * HTHost_channel (HTHost * host);
359: </PRE>
360: <H3>
2.8 frystyk 361: Read Management
362: </H3>
363: <PRE>
364: extern int HTHost_read(HTHost * host, HTNet * net);
365: extern BOOL HTHost_setConsumed(HTHost * host, size_t bytes);
2.3 frystyk 366: </PRE>
2.12 frystyk 367: <H2>
368: Multi homed Host Management
369: </H2>
370: <P>
371: We also keep track of if a host has multiple IP addresses. If so then it
372: is called a <I>multi-homed host</I>. This is used for two things: finding
373: the fastest host with this name and as a backup if one or more of the hosts
374: are down.
2.1 frystyk 375: <PRE>
2.12 frystyk 376: extern BOOL HTHost_setHome (HTHost * host, int home);
377: extern int HTHost_home (HTHost * host);
2.13 frystyk 378:
379: extern BOOL HTHost_setRetry (HTHost * host, int retry);
380: extern int HTHost_retry (HTHost * host);
381: extern BOOL HTHost_decreaseRetry (HTHost * host);
2.12 frystyk 382: </PRE>
383: <PRE>
2.1 frystyk 384: #endif /* HTHOST_H */
385: </PRE>
2.3 frystyk 386: <P>
387: <HR>
2.1 frystyk 388: <ADDRESS>
2.15 ! frystyk 389: @(#) $Id: HTHost.html,v 2.14 1997/02/16 18:42:24 frystyk Exp $
2.1 frystyk 390: </ADDRESS>
2.3 frystyk 391: </BODY></HTML>
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