Annotation of libwww/Library/src/HTFWrite.html, revision 2.6
2.1 frystyk 1: <HTML>
2: <HEAD>
2.2 frystyk 3: <TITLE>Cache Manager and Writing to a File using ANSI C</TITLE>
2.6 ! frystyk 4: <!-- Changed by: Henrik Frystyk Nielsen, 28-Jun-1995 -->
2.1 frystyk 5: <NEXTID N="z4">
6: </HEAD>
7: <BODY>
8:
2.2 frystyk 9: <H1>Cache Manager and Writing to a File using ANSI C</H1>
2.1 frystyk 10:
11: <PRE>
12: /*
2.4 frystyk 13: ** (c) COPYRIGHT MIT 1995.
2.1 frystyk 14: ** Please first read the full copyright statement in the file COPYRIGH.
15: */
16: </PRE>
17:
18: It is useful to have both FWriter and Writer for environments in which
2.2 frystyk 19: <CODE>fdopen()</CODE> doesn't exist for example. The module contains
20: the following parts:
21:
22: <UL>
23: <LI><A HREF="#BlackHole">A Balckhole for absorbing data</A>
24: <LI><A HREF="#write">A File Writer Stream</A>
25: <LI><A HREF="#converters">Converters using the file writer stream</A>
26: <LI><A HREF="#z3">Cache Manager</A>
27: </UL>
28:
2.1 frystyk 29:
30: This module is implemented by <A HREF="HTFWrite.c">HTFWrite.c</A>,
31: and it is a part of the <A
2.2 frystyk 32: HREF="http://www.w3.org/hypertext/WWW/Library/User/Guide/Guide.html">
2.1 frystyk 33: Library of Common Code</A>.
34:
35:
36: <PRE>
37: #ifndef HTFWRITE_H
38: #define HTFWRITE_H
39:
40: #include "HTStream.h"
41: #include "HTFormat.h"
42: </PRE>
43:
2.2 frystyk 44: <H2><A NAME="BlackHole">Black Hole Stream</A></H2>
45:
46: This stream simply absorbs data without doing anything what so ever.
47:
48: <PRE>
49: extern HTStream * HTBlackHole NOPARAMS;
50: </PRE>
51:
2.5 frystyk 52: <A NAME="converters"><H2>Converters</H2></A>
2.1 frystyk 53:
2.5 frystyk 54: This is the set of functions that can be registered as
55: converters. Note that the cache writer stream is also a converter!
2.1 frystyk 56:
2.5 frystyk 57: <PRE>
58: #ifndef pyramid
59: extern HTConverter HTSaveAndExecute, HTSaveLocally, HTSaveAndCallBack,
60: HTThroughLine, HTCacheWriter;
61: #endif
2.1 frystyk 62: </PRE>
63:
2.5 frystyk 64: <A NAME="tmp"><H2>Location of Temporary Files</H2></A>
2.1 frystyk 65:
2.2 frystyk 66: <CODE>HTSaveAndCallBack</CODE> will save to a cache file and call the
67: request->callback function with the filename as parameter. The
68: destination for temporary files can be managed by the following
69: functions:
70:
71: <PRE>
72: extern BOOL HTTmp_setRoot PARAMS((CONST char * tmp_root));
73: extern CONST char * HTTmp_getRoot NOPARAMS;
74: extern void HTTmp_freeRoot NOPARAMS;
75: </PRE>
76:
77: The <CODE>HTTmp_freeRoot</CODE> is called by the <A
2.5 frystyk 78: HREF="HTAccess.html#Library">HTLibTerminate</A> function. The default
79: value is defined in <A
80: HREF="HTAccess.html#Addresses">HTAccess.html</A>
2.1 frystyk 81:
2.5 frystyk 82: <H2><A NAME="write">Set up a Stream to a File</A></H2>
2.1 frystyk 83:
2.5 frystyk 84: This function puts up a new stream given an open file descripter. If the file
85: is not to be closed afterwards, then set leave_open = NO.
2.1 frystyk 86:
2.5 frystyk 87: <PRE>extern HTStream * HTFWriter_new PARAMS((FILE * fp,
88: BOOL leave_open));
2.1 frystyk 89: </PRE>
90:
2.2 frystyk 91: <H2><A NAME="z3">The Cache Manager</A></H2>
2.1 frystyk 92:
2.2 frystyk 93: The cache contains details of temporary disk files which contain the
94: contents of remote documents. There is also a <A NAME="z2"
95: HREF="HTAnchor.html#z1">list of cache items for each URL</A> in its
96: anchor object.
2.1 frystyk 97:
2.6 ! frystyk 98: <A NAME="cacheitem"><H3>An item in the cache</H3></A>
2.2 frystyk 99:
100: This will not be public in the next release so <B>DON'T USE IT ;-)</B>
101:
2.1 frystyk 102: <PRE>typedef struct _HTCacheItem {
103: HTParentAnchor * anchor;
104: HTFormat format; /* May have many formats per anchor */
105: char * filename;
106: time_t load_time;
107: time_t load_delay;
108: int reference_count;
109: } HTCacheItem;
2.2 frystyk 110: </PRE>
111:
112: <H3>The Cache Limit</H3>
2.1 frystyk 113:
2.2 frystyk 114: The cache limit is the number of files which are kept. Yes, I know,
2.6 ! frystyk 115: the amount of disk space would be more relevant. So this may change.
2.2 frystyk 116: Currently it is preset to 100 but may be changed by the application by
117: writing into this variable.
118:
119: <PRE>
120: extern int HTCacheLimit;
2.1 frystyk 121: </PRE>
122:
2.2 frystyk 123: <H3>Enable Cache</H3>
124:
125: If <EM>cache_root</EM> is NULL then reuse old value or use
126: <CODE>HT_CACHE_ROOT</CODE>. An empty string will make '/' as cache
127: root.
128:
129: <PRE>
130: extern BOOL HTCache_enable PARAMS((CONST char * cache_root));
2.1 frystyk 131: </PRE>
132:
2.2 frystyk 133: <H3>Disable Cache</H3>
134:
135: Turns off the cache. Note that the cache can be disabled and enabled
136: at any time. The cache root is kept and can be reused during the
137: execution.
138:
139: <PRE>
140: extern BOOL HTCache_disable NOPARAMS;
141: </PRE>
142:
143: <H3>Is Cache Enabled</H3>
144:
145: Returns YES or NO. Also makes sure that we have a root value (even
146: though it might be invalid)
147:
148: <PRE>
149: extern BOOL HTCache_isEnabled NOPARAMS;
150: </PRE>
151:
152: <H3>Set Cache Root</H3>
153:
154: If <EM>cache_root</EM> is NULL then the current value (might be a define)
155: Should we check if the cache_root is actually OK? I think not!
156:
157: <PRE>
158: extern BOOL HTCache_setRoot PARAMS((CONST char * cache_root));
159: </PRE>
160:
161:
162: <H3>Get Cache Root</H3>
163:
164: <PRE>
165: extern CONST char *HTCache_getRoot NOPARAMS;
2.1 frystyk 166: </PRE>
167:
2.2 frystyk 168: <H3>For clean up memory</H3>
169:
170: This is done by the Library function <A
171: HREF="HTAccess.html#Library">HTLibTerminate()</A>
172:
173: <PRE>
174: extern void HTCache_freeRoot NOPARAMS;
2.1 frystyk 175: </PRE>
2.2 frystyk 176:
177: <H3>Clear a cache</H3>
178:
179: Can clear a list of cache items.
180:
2.1 frystyk 181: <PRE>
2.2 frystyk 182: extern void HTCacheClear PARAMS((HTList * cache));
2.1 frystyk 183: </PRE>
184:
2.2 frystyk 185: <H3>To remove All cache files known to this session</H3>
2.1 frystyk 186:
187: <PRE>
2.2 frystyk 188: extern void HTCacheDeleteAll NOPARAMS;
2.1 frystyk 189:
190: #endif
191: </PRE>
192:
193: End of definition module
194: </BODY>
195: </HTML>
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