Annotation of libwww/Library/src/HTCache.html, revision 2.7
2.1 frystyk 1: <HTML>
2: <HEAD>
2.2 frystyk 3: <TITLE>Disk Cache Manager</TITLE>
2.6 frystyk 4: <!-- Changed by: Henrik Frystyk Nielsen, 14-Nov-1995 -->
2.1 frystyk 5: <NEXTID N="z4">
6: </HEAD>
7: <BODY>
8:
2.2 frystyk 9: <H1>Disk Cache Manager</H1>
2.1 frystyk 10:
11: <PRE>
12: /*
13: ** (c) COPYRIGHT MIT 1995.
14: ** Please first read the full copyright statement in the file COPYRIGH.
15: */
16: </PRE>
17:
18: The cache contains details of temporary disk files which contain the
19: contents of remote documents. There is also a <A
20: HREF="HTAnchor.html#z1">list of cache items for each URL</A> in its
21: anchor object. <P>
22:
23: This module is implemented by <A HREF="HTCache.c">HTCache.c</A>, and
2.6 frystyk 24: it is a part of the <A HREF="http://www.w3.org/pub/WWW/Library/">W3C
25: Reference Library</A>.
2.1 frystyk 26:
27: <PRE>
28: #ifndef HTCACHE_H
29: #define HTCACHE_H
30:
31: #include "HTStream.h"
32: #include "HTAnchor.h"
33: #include "HTFormat.h"
2.4 frystyk 34: #include "HTReq.h"
2.1 frystyk 35: </PRE>
36:
37: <H2>Converters</H2>
38:
39: The cache stream is in fact a stream that can be registered as a converter!
40:
41: <PRE>
42: extern HTConverter HTCacheWriter;
43: </PRE>
44:
2.4 frystyk 45: <H3>How do we handle Expires header?</H3>
46:
47: There are various ways of handling Expires header when met in a
48: history list. Either it can be ignored all together, the user can be
49: notified with a warning, or the document can be reloaded
50: automatically. This flag decides what action to be taken. The default
51: action is HT_EXPIRES_IGNORE. In HT_EXPIRES_NOTIFY mode you can specify
52: a message to tell the user (NULL is valid in which case my own message
53: pops up - watch out it might be in Danish ;-))
54:
55: <PRE>
56: typedef enum _HTExpiresMode {
57: HT_EXPIRES_IGNORE = 0,
58: HT_EXPIRES_NOTIFY,
59: HT_EXPIRES_AUTO
60: } HTExpiresMode;
61:
62: extern void HTCache_setExpiresMode (HTExpiresMode mode, char * notify);
63: extern HTExpiresMode HTCache_expiresMode (char ** notify);
64: </PRE>
65:
66: <A NAME="memcache"><H2>Memory cache Management</H2></A>
67:
68: The Library has two notions of a local cache: a file cache and a
69: memory cache. The memory cache is handled by the client and the file
70: cache is handled by the Library. Often the format of a object cached
71: in memory is in the form of a hypertext object ready to be displayed
72: (that is, it's already parsed). However, this is not required, and the
73: application can therefore register a memory cache handler that returns
74: an int with the following values:
75:
76: <UL>
77: <LI>HT_LOADED if the document is in memory and is OK
78: <LI>HT_ERROR if the document is not in memory
79: </UL>
80:
81: <PRE>
82: typedef int HTMemoryCacheHandler (HTRequest * request,
83: HTExpiresMode mode,
84: char * message);
85:
86: extern int HTMemoryCache_check (HTRequest * request);
87: extern BOOL HTMemoryCache_register (HTMemoryCacheHandler * cbf);
88: extern BOOL HTMemoryCache_unRegister (void);
89: </PRE>
90:
2.2 frystyk 91: <H2>Find a Reference for a Cached Object</H2>
2.1 frystyk 92:
2.2 frystyk 93: Verifies if a cache object exists for this URL and if so returns a URL
94: for the cached object. It does not verify whether the object is valid
95: or not, for example it might have been expired.
2.1 frystyk 96:
97: <PRE>
2.6 frystyk 98: extern char * HTCache_getReference (char * url);
2.2 frystyk 99: </PRE>
100:
101: <H2>Verify if an Object is Valid</H2>
102:
103: This function checks whether a document has expired or not. The check
104: is based on the metainformation passed in the anchor object The
105: function returns YES or NO.
106:
107: <PRE>
2.6 frystyk 108: extern BOOL HTCache_isValid (HTParentAnchor * anchor);
2.1 frystyk 109: </PRE>
110:
111: <H2>Enable Cache</H2>
112:
113: If <EM>cache_root</EM> is NULL then reuse old value or use
114: <CODE>HT_CACHE_ROOT</CODE>. An empty string will make '/' as cache
115: root.
116:
117: <PRE>
2.7 ! frystyk 118: extern BOOL HTCache_enable (const char * cache_root);
2.1 frystyk 119: </PRE>
120:
121: <H2>Disable Cache</H2>
122:
123: Turns off the cache. Note that the cache can be disabled and enabled
124: at any time. The cache root is kept and can be reused during the
125: execution.
126:
127: <PRE>
2.6 frystyk 128: extern BOOL HTCache_disable (void);
2.1 frystyk 129: </PRE>
130:
131: <H2>Is Cache Enabled</H2>
132:
133: Returns YES or NO. Also makes sure that we have a root value (even
134: though it might be invalid)
135:
136: <PRE>
2.6 frystyk 137: extern BOOL HTCache_isEnabled (void);
2.1 frystyk 138: </PRE>
139:
140: <H2>Set Cache Root</H2>
141:
142: If <EM>cache_root</EM> is NULL then the current value (might be a define)
143: Should we check if the cache_root is actually OK? I think not!
144:
145: <PRE>
2.7 ! frystyk 146: extern BOOL HTCache_setRoot (const char * cache_root);
2.1 frystyk 147: </PRE>
148:
149: <H2>Get Cache Root</H2>
150:
151: <PRE>
2.7 ! frystyk 152: extern const char *HTCache_getRoot (void);
2.1 frystyk 153: </PRE>
154:
2.2 frystyk 155: <H2>Clean up memory</H2>
2.1 frystyk 156:
157: This is done by the Library function <A
2.4 frystyk 158: HREF="HTReq.html#Library">HTLibTerminate()</A>. None of these
2.2 frystyk 159: functions tourches the disk cache itself - they only manages memory.
2.1 frystyk 160:
161: <PRE>
2.6 frystyk 162: extern void HTCache_freeRoot (void);
163: extern void HTCache_clearMem (void);
2.1 frystyk 164: </PRE>
165:
2.2 frystyk 166: <H2>To remove All cache files known to this session</H2>
2.1 frystyk 167:
2.2 frystyk 168: This function also cleans the entries on disk
2.1 frystyk 169:
170: <PRE>
2.6 frystyk 171: extern void HTCache_deleteAll (void);
2.1 frystyk 172:
173: #endif
174: </PRE>
175:
176: End of declaration module
177: </BODY>
178: </HTML>
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