Annotation of libwww/Library/src/HTFilter.html, revision 2.1
2.1 ! frystyk 1: <HTML>
! 2: <HEAD>
! 3: <!-- Changed by: Henrik Frystyk Nielsen, 5-Jul-1996 -->
! 4: <TITLE>W3C Reference Library libwww BEFORE and AFTER Filters</TITLE>
! 5: </HEAD>
! 6: <BODY>
! 7: <H1>
! 8: Standard BEFORE and AFTER Filters
! 9: </H1>
! 10: <PRE>
! 11: /*
! 12: ** (c) COPYRIGHT MIT 1995.
! 13: ** Please first read the full copyright statement in the file COPYRIGH.
! 14: */
! 15: </PRE>
! 16: <P>
! 17: This module provides a set of default <B>BEFORE</B> and <B>AFTER</B> filters
! 18: that can be registered by the <A HREF="HTNet.html">Net manager</A> to be
! 19: called before and after a request. All filters can be registered either to
! 20: be called <I>globally</I> (all requests) or <I>locally</I> (pr request basis).
! 21: <P>
! 22: This module is implemented by <A HREF="HTFilter.c">HTFilter.c</A>, and it
! 23: is a part of the <A HREF="http://www.w3.org/pub/WWW/Library/"> W3C Reference
! 24: Library</A>.
! 25: <PRE>
! 26: #ifndef HTFILTER_H
! 27: #define HTFILTER_H
! 28: #include "WWWLib.h"
! 29: </PRE>
! 30: <H2>
! 31: BEFORE Filters
! 32: </H2>
! 33: <P>
! 34: This is a standard set of <B>BEFORE</B> filters which the application may
! 35: initialize. This can be done in an easy way using the function
! 36: <CODE>HTBeforeInit()</CODE> in the <A HREF="WWWInit.html">Initialization
! 37: interface</A>.
! 38: <H3>
! 39: Proxy and Gateway BEFORE filter
! 40: </H3>
! 41: <P>
! 42: Checks for registerd proxy servers or gateways and sees whether this request
! 43: should be redirected to a proxy or a gateway. Proxies have higher priority
! 44: than gateways so we look for them first! For HTTP/1.0 and HTTP/1.1 we may
! 45: only send a full URL (including the host portion) to proxy servers. Therefore,
! 46: we tell the Library whether to use the full URL or the traditional HTTP one
! 47: without the host part.
! 48: <PRE>
! 49: extern int HTProxyFilter (HTRequest * request, void * param, int status);
! 50: </PRE>
! 51: <H3>
! 52: Rule Translation BEFORE Filter
! 53: </H3>
! 54: <P>
! 55: If we have a set of rules loaded (see the Rule manager) then check before
! 56: each request whether how that should be translated. The trick is that a parent
! 57: anchor has a "address" which is the part from the URL we used when we created
! 58: the anchor. However, it also have a "physical address" which is the place
! 59: we are actually going to look for the resource. Hence this filter translates
! 60: from the address to the physical address (if any translations are found)
! 61: <PRE>
! 62: extern int HTRuleFilter (HTRequest * request, void * param, int status);
! 63: </PRE>
! 64: <H3>
! 65: Cache Validation BEFORE Filter
! 66: </H3>
! 67: <P>
! 68: Check the cache mode to see if we can use an already loaded version of this
! 69: document. If so and our copy is valid then we don't have to go out and get
! 70: it unless we are forced to
! 71: <PRE>
! 72: extern int HTCacheFilter (HTRequest * request, void * param, int status);
! 73: </PRE>
! 74: <H3>
! 75: Client side authentication BEFORE filter
! 76: </H3>
! 77: <P>
! 78: The filter generates the credentials required to access a document Getting
! 79: the credentials may involve asking the user in which case we use the methods
! 80: registered by the <A HREF="HTAlert.html">HTAlert module</A>
! 81: <PRE>
! 82: extern int HTCredentialsFilter (HTRequest * request, void * param, int status);
! 83: </PRE>
! 84: <H2>
! 85: AFTER Filters
! 86: </H2>
! 87: <P>
! 88: Like <B>BEFORE</B> filters we provide a default set of typical <B>AFTER</B>
! 89: filters that may be initialized by the application. Again, an easy way of
! 90: doing this is to call the <CODE>HTAfterInit()</CODE> function in the
! 91: <A HREF="WWWInit.html">Initialization interface</A>.
! 92: <H3>
! 93: Error and Information filter
! 94: </H3>
! 95: <P>
! 96: It checks the status code from a request and generates an error/information
! 97: message if required.
! 98: <PRE>
! 99: extern int HTInfoFilter (HTRequest * request, void * param, int status);
! 100: </PRE>
! 101: <H3>
! 102: Redirection filter
! 103: </H3>
! 104: <P>
! 105: The redirection handler only handles redirections on the <CODE>GET</CODE>
! 106: or <CODE>HEAD</CODE> method (or any other safe method)
! 107: <PRE>
! 108: extern int HTRedirectFilter (HTRequest * request, void * param, int status);
! 109: </PRE>
! 110: <H3>
! 111: Client side authentication filter
! 112: </H3>
! 113: <P>
! 114: The client side authentication filter uses the user dialog messages registered
! 115: in the <A HREF="HTAlert.html">HTAlert module</A>. By default these are the
! 116: ones used by the line mode browser but you can just register something else.
! 117: <PRE>
! 118: extern int HTAuthFilter (HTRequest * request, void * param, int status);
! 119: </PRE>
! 120: <H3>
! 121: Request Logging filter
! 122: </H3>
! 123: <P>
! 124: Default Logging filter using the log manager provided by the
! 125: <A HREF="HTLog.html">Log Manager</A>.
! 126: <PRE>
! 127: extern int HTLogFilter (HTRequest * request, void * param, int stutus);
! 128: </PRE>
! 129: <PRE>
! 130: #endif /* HTFILTER_H */
! 131: </PRE>
! 132: <P>
! 133: <HR>
! 134: <ADDRESS>
! 135: @(#) $Id: HTHome.html,v 2.9 1996/07/04 18:40:18 frystyk Exp $
! 136: </ADDRESS>
! 137: </BODY></HTML>
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