Mercurial > noffle

changeset 128:8897b7e3b108 noffle

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
[svn] Add article filtering
author bears
date Wed, 09 Aug 2000 22:19:17 +0100
parents 3c71e28c8eef
children 6b2b93288caa
files docs/noffle.conf.5 src/Makefile.in src/configfile.c src/filter.c src/filter.h
diffstat 5 files changed, 706 insertions(+), 12 deletions(-) [+]
line wrap: on
line diff
--- a/docs/noffle.conf.5	Tue Jul 25 13:14:54 2000 +0100
+++ b/docs/noffle.conf.5	Wed Aug 09 22:19:17 2000 +0100
@@ -1,5 +1,5 @@
 .TH noffle.conf 5
-.\" $Id: noffle.conf.5 155 2000-06-24 20:28:01Z bears $
+.\" $Id: noffle.conf.5 189 2000-08-09 21:19:17Z bears $
 
 .SH NAME
 noffle.conf \- Configuration file for NOFFLE news server
@@ -203,6 +203,17 @@
 .br
 Default: no
 
+.TP
+.B filter <filter specification>
+Add the specified filter to the list of filters to be applied to incoming
+articles. Filters are applied in the order in which they appear in
+.I /etc/noffle.conf
+and are further described in the section
+.B FILTERS
+below.
+.br
+Default: No filters
+
 .SH "GROUP NAME WILDCARDS"
 
 .B NOFFLE
@@ -254,10 +265,110 @@
 .I [^]\-]
 matches any character other than a close bracket or minus sign.
 
+.SH FILTERS
+
+.B NOFFLE
+supports basic filtering on incoming articles. Articles to be downloaded
+can be matched against one or more criteria and matching articles are
+marked for download using one of the group subscribe modes
+.BR full ,
+.B over
+or
+.BR thread .
+Alternatively the filter may specify that the article mode is
+.B discard
+in which case neither the article nor the article overview will
+be downloaded.
+
+.PP
+A
+.B filter
+configuration line consist of one or more filter specifications
+following the
+.B filter
+keyword on the line. The available specifications are:
+
+.PP
+.B action
+=
+.IR "full|over|thread|discard" .
+Specifies the action to be taken if the filter matches. If not specified,
+the default action is as specified by the group's default subscription mode.
+.PP
+.B group
+=
+.IR "<group pattern>" .
+Matches if any group in which the article appears matches the
+specified group pattern.
+.PP
+.B subject
+=
+.IR "<regular expression>" .
+Matches if the article subject matches the given regular expression.
+See the section on regular expressions below.
+.PP
+.B from
+=
+.IR "<regular expression>" .
+Matches if the article subject matches the given regular expression.
+See the section on regular expressions below.
+.PP
+.B msgid
+=
+.IR "<regular expression>" .
+Matches if the article message ID matches the given regular expression.
+See the section on regular expressions below.
+.PP
+.B bytes
+< or = or >
+.IR <number> .
+Matches if the number of bytes in the article is less than, equal to, or
+greater than the given number.
+.PP
+.B lines
+< or = or >
+.IR <number> .
+Matches if the number of lines in the article is less than, equal to, or
+greater than the given number.
+.PP
+.B refs
+< or = or >
+.IR <number> .
+Matches if the number of articles referenced by the article is less
+than, equal to, or greater than the given number.
+.PP
+.B xposts
+< or = or >
+.IR <number> .
+Matches if the number of groups the article is posted to is less
+than, equal to, or greater than the given number.
+
+.PP
+For example, the following filters download all articles in groups
+in the alt.binaries tree in full if they are < 10k in size, otherwise
+downloads overviews.
+.PP
+.I filter group=alt.binaries.* bytes < 10240 action=full
+.br
+.I filter group=alt.binaries.* action=over
+.PP
+This filter discards all articles with a subject resembling
+the infamous "$$$ Make Money Now! $$$".
+.PP
+\fIfilter subject="\\$*.*Make.*[M|m]oney.*\\$" action=discard\fR
+
+.SH REGULAR EXPRESSIONS
+
+.B NOFFLE
+uses extended POSIX-style regular expressions in its filters. Regular
+expressions are a powerful means of describing patterns that match
+text. A full description is to be found in 
+.BR regex (7).
 
 .SH SEE ALSO
 
 .BR noffle (1)
+.BR regex (7)
 
 .SH AUTHORS
 
--- a/src/Makefile.in	Tue Jul 25 13:14:54 2000 +0100
+++ b/src/Makefile.in	Wed Aug 09 22:19:17 2000 +0100
@@ -72,7 +72,7 @@
 
 bin_PROGRAMS = noffle
 
-noffle_SOURCES =  client.c client.h common.h configfile.c configfile.h content.c content.h control.c control.h database.c database.h dynamicstring.c dynamicstring.h fetch.c fetch.h fetchlist.c fetchlist.h group.c group.h itemlist.c itemlist.h lock.c lock.h log.c log.h noffle.c online.c online.h outgoing.c outgoing.h over.c over.h portable.h post.c post.h protocol.c protocol.h pseudo.c pseudo.h request.c request.h server.c server.h util.c util.h wildmat.c wildmat.h
+noffle_SOURCES =  client.c client.h common.h configfile.c configfile.h content.c content.h control.c control.h database.c database.h dynamicstring.c dynamicstring.h fetch.c fetch.h fetchlist.c fetchlist.h filter.c filter.h group.c group.h itemlist.c itemlist.h lock.c lock.h log.c log.h noffle.c online.c online.h outgoing.c outgoing.h over.c over.h portable.h post.c post.h protocol.c protocol.h pseudo.c pseudo.h request.c request.h server.c server.h util.c util.h wildmat.c wildmat.h
 
 
 noffle_LDADD = -lgdbm
@@ -87,7 +87,7 @@
 LDFLAGS = @LDFLAGS@
 LIBS = @LIBS@
 noffle_OBJECTS =  client.o configfile.o content.o control.o database.o \
-dynamicstring.o fetch.o fetchlist.o group.o itemlist.o lock.o log.o \
+dynamicstring.o fetch.o fetchlist.o filter.o group.o itemlist.o lock.o log.o \
 noffle.o online.o outgoing.o over.o post.o protocol.o pseudo.o \
 request.o server.o util.o wildmat.o
 noffle_DEPENDENCIES = 
@@ -105,7 +105,7 @@
 GZIP_ENV = --best
 DEP_FILES =  .deps/client.P .deps/configfile.P .deps/content.P \
 .deps/control.P .deps/database.P .deps/dynamicstring.P .deps/fetch.P \
-.deps/fetchlist.P .deps/group.P .deps/itemlist.P .deps/lock.P \
+.deps/fetchlist.P .deps/filter.P .deps/group.P .deps/itemlist.P .deps/lock.P \
 .deps/log.P .deps/noffle.P .deps/online.P .deps/outgoing.P .deps/over.P \
 .deps/post.P .deps/protocol.P .deps/pseudo.P .deps/request.P \
 .deps/server.P .deps/util.P .deps/wildmat.P
--- a/src/configfile.c	Tue Jul 25 13:14:54 2000 +0100
+++ b/src/configfile.c	Wed Aug 09 22:19:17 2000 +0100
@@ -6,7 +6,7 @@
     SPOOLDIR
     VERSION
 
-  $Id: configfile.c 155 2000-06-24 20:28:01Z bears $
+  $Id: configfile.c 189 2000-08-09 21:19:17Z bears $
 */
 
 #if HAVE_CONFIG_H
@@ -17,6 +17,8 @@
 
 #include <ctype.h>
 #include <limits.h>
+#include <regex.h>
+#include "filter.h"
 #include "itemlist.h"
 #include "log.h"
 #include "util.h"
@@ -554,6 +556,184 @@
     config.autoSubscribeMode[ config.numAutoSubscribeMode++ ] = entry;
 }
 
+static const char *
+getToken( const char *line, Str value )
+{
+    Bool isQuoted;
+    char quoteChar;
+    Bool seenEscape;
+    char *maxVal;
+    
+    while ( *line != '\0' && isspace( *line ) )
+	line++;
+    if ( *line == '\0' )
+	return NULL;
+
+    maxVal = &value[ MAXCHAR ];
+    isQuoted = ( *line == '\'' || *line == '"' );
+    if ( isQuoted )
+    {
+	quoteChar = *line;
+	line++;
+
+	seenEscape = FALSE;
+	while ( *line != '\0'
+		&& ( *line != quoteChar || seenEscape )
+		&& value < maxVal )
+	{
+	    if ( seenEscape )
+	    {
+		*value++ = *line;
+		seenEscape = FALSE;
+	    }
+	    else
+	    {
+		if ( *line == '\\' )
+		    seenEscape = TRUE;
+		else
+		    *value++ = *line;
+	    }
+	    line++;
+	}
+
+	if ( *line == quoteChar )
+	    line++;
+    }
+    else
+    {
+	while ( *line != '\0' && ! isspace( *line ) && value < maxVal )
+	    *value++ = *line++;
+    }
+    *value = '\0';
+    return line;
+}
+
+static void
+getFilter( const char *line )
+{
+    Str ruleBuf, value;
+    const char *l;
+    char *p, *ruleName;
+    Filter *f;
+    FilterRule rule;
+    Bool seenAction;
+
+    f = new_Filter();
+    
+    /* Skip "filter" */
+    l = Utl_restOfLn( line, 1 );
+    seenAction = FALSE;
+    
+    for(;;)
+    {
+	while ( *l != '\0' && isspace( *l ) )
+	    l++;
+
+	if ( *l == '\0' )
+	    break;
+	
+	/* Get the rule title */
+	p = ruleBuf;
+	while ( *l != '\0' && *l != '=' && *l != '<' && *l != '>' )
+	    *p++ = *l++;
+	*p = '\0';
+	ruleName = Utl_stripWhiteSpace( ruleBuf );
+	Utl_toLower( ruleName );
+
+	if ( *ruleName == '\0' )
+	    goto synErr;
+
+	/* Do we know this rule? */
+	if ( strcmp( ruleName, "group" ) == 0 )
+	    rule.type = RULE_NEWSGROUP;
+	else if ( strcmp( ruleName, "subject" ) == 0 )
+	    rule.type = RULE_SUBJECT;
+	else if ( strcmp( ruleName, "from" ) == 0 )
+	    rule.type = RULE_FROM;
+	else if ( strcmp( ruleName, "msgid" ) == 0 )
+	    rule.type = RULE_MSGID;
+	else if ( strcmp( ruleName, "bytes" ) == 0 )
+	    rule.type = RULE_BYTES_LT;
+	else if ( strcmp( ruleName, "lines" ) == 0 )
+	    rule.type = RULE_LINES_LT;
+	else if ( strcmp( ruleName, "refs" ) == 0 )
+	    rule.type = RULE_NOREFS_LT;
+	else if ( strcmp( ruleName, "xposts" ) == 0 )
+	    rule.type = RULE_XPOSTS_LT;
+	else if ( strcmp( ruleName, "action" ) != 0 )
+	    goto synErr;
+
+	if ( rule.type == RULE_BYTES_LT ||
+	     rule.type == RULE_LINES_LT ||
+	     rule.type == RULE_NOREFS_LT ||
+	     rule.type == RULE_XPOSTS_LT )
+	{
+	    if ( *l == '=' )
+		rule.type += 1;
+	    else if ( *l == '>' )
+		rule.type += 2;
+	    else if ( *l != '<' )
+		goto synErr;
+	}
+	else if ( *l != '=' )
+	    goto synErr;
+
+	/* Skip past '=' (or '>' or '<') */
+	l++;
+	
+	/* OK, we now have a valid rule. What value? */
+	l = getToken( l, value );
+	if ( l == NULL )
+	    goto synErr;
+
+	if ( strcmp( ruleName, "action" ) == 0 )
+	{
+	    if ( seenAction )
+		goto synErr;
+	    
+	    Utl_toLower( value );
+	    if ( strcmp( value, "full" ) == 0 )
+		f->action = FILTER_FULL;
+	    else if ( strcmp( value, "over" ) == 0 )
+		f->action = FILTER_XOVER;
+	    else if ( strcmp( value, "thread" ) == 0 )
+		f->action = FILTER_THREAD;
+	    else if ( strcmp( value, "discard" ) == 0 )
+		f->action = FILTER_DISCARD;
+	    seenAction = TRUE;
+	}
+	else if ( rule.type == RULE_NEWSGROUP )
+	    Utl_allocAndCpy( &rule.data.grp, value );
+	else if ( rule.type >= RULE_SUBJECT && rule.type <= RULE_MSGID )
+	{
+	    if ( regcomp( &rule.data.regex, value, REG_EXTENDED ) != 0 )
+		goto synErr;
+	}
+	else
+	{
+	    char * endVal;
+
+	    rule.data.amount = strtoul( value, &endVal, 0 );
+	    if ( *endVal != '\0' && ! isspace( *endVal ) )
+		goto synErr;
+	}
+
+	if ( strcmp( ruleName, "action" ) != 0 )
+	{
+	    Log_dbg( "Adding rule type %d value %s", rule.type, value );
+	    Flt_addRule( f, rule );
+	}
+    }
+
+    Log_dbg( "Adding filter, action %d", f->action );
+    Flt_addFilter( f );
+    return;
+    
+synErr:
+    logSyntaxErr( line );
+    return;
+}
+
 void
 Cfg_read( void )
 {
@@ -573,6 +753,7 @@
 	Utl_stripComment( p );
         Utl_cpyStr( lowerLine, p );
         Utl_toLower( lowerLine );
+	p = lowerLine;
         if ( *p == '\0' )
             continue;
         if ( sscanf( p, "%s", name ) != 1 )
@@ -600,7 +781,6 @@
         else if ( strcmp( "default-auto-subscribe-mode", name ) == 0 )
         {
             getStr( s, p );
-            Utl_toLower( s );
 	    if ( ! isValidAutoSubscribeMode( s ) )
 	    {
 		logSyntaxErr( line );
@@ -609,14 +789,8 @@
             else
                 strcpy( config.defaultAutoSubscribeMode, s );
         }
-        else if ( strcmp( "server", name ) == 0 )
-            /* Server needs line not p,
-               because password may contain uppercase */
-            getServ( line );
         else if ( strcmp( "mail-to", name ) == 0 )
             getStr( config.mailTo, p );
-        else if ( strcmp( "path-header", name ) == 0 )
-            getStr( config.pathHeader, p );
         else if ( strcmp( "expire", name ) == 0 )
             getExpire( p );
         else if ( strcmp( "auto-subscribe-mode", name ) == 0 )
@@ -625,6 +799,13 @@
             getGroups( p, TRUE );
         else if ( strcmp( "omitgroups", name ) == 0 )
             getGroups( p, FALSE );
+	/* The following need line because they may have uppercase data */
+        else if ( strcmp( "server", name ) == 0 )
+            getServ( line );
+        else if ( strcmp( "path-header", name ) == 0 )
+            getStr( config.pathHeader, p );
+	else if ( strcmp( "filter", name ) == 0 )
+	    getFilter( line );
         else
             Log_err( "Unknown config option: %s", name );
     }
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/filter.c	Wed Aug 09 22:19:17 2000 +0100
@@ -0,0 +1,307 @@
+/*
+  filter.c
+  
+  Article filtering.
+  
+  $Id: filter.c 189 2000-08-09 21:19:17Z bears $
+*/
+
+#if HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "filter.h"
+
+#include <ctype.h>
+#include "common.h"
+#include "itemlist.h"
+#include "log.h"
+#include "wildmat.h"
+
+struct
+{
+    int nFilters;
+    int maxFilters;
+    const Filter **filters;
+    Bool needGroups;
+} filter = { 0, 0, NULL, FALSE };
+
+static unsigned long
+countGroups( const char *grps )
+{
+    unsigned long res;
+
+    res = 1;
+    while ( *grps != '\0' )
+    {
+	if ( *grps == ',' )
+	    res++;
+	grps++;
+    }
+
+    return res;
+}
+static unsigned long
+countRefs( const char *refs )
+{
+    unsigned long res;
+    Bool inRef;
+
+    res = 0;
+    inRef = FALSE;
+
+    while ( *refs != '\0' )
+    {
+	if ( inRef )
+	{
+	    if ( *refs == '>' )
+	    {
+		inRef = FALSE;
+		res++;
+	    }
+	}
+	else if ( *refs == '<' )
+	    inRef = TRUE;
+	refs++;
+    }
+
+    return res;
+}
+
+/* Check a single rule to see if it passes. */
+static Bool
+checkRule( const char *thisGrp, const char *newsgroups,
+	   const Over *ov, const FilterRule *r )
+{
+    unsigned long ul;
+    ItemList *grps;
+    const char *p;
+    
+    switch( r->type )
+    {
+    case RULE_NEWSGROUP:
+	if ( Wld_match( thisGrp, r->data.grp ) )
+	    return TRUE;
+	if ( newsgroups != NULL )
+	{
+	    grps = new_Itl( newsgroups, " ,\t" );
+	    for ( p = Itl_first( grps ); p != NULL; p = Itl_next( grps ) )
+		if ( Wld_match( p, r->data.grp ) )
+		     return TRUE;
+	    del_Itl( grps );
+	}
+	return FALSE;
+
+    case RULE_SUBJECT:
+	return ( regexec( &r->data.regex, Ov_subj( ov ), 0, NULL, 0 ) == 0 );
+
+    case RULE_FROM:
+	return ( regexec( &r->data.regex, Ov_from( ov ), 0, NULL, 0 ) == 0 );
+
+    case RULE_BYTES_LT:
+	return ( Ov_bytes( ov ) < r->data.amount );
+
+    case RULE_BYTES_EQ:
+	return ( Ov_bytes( ov ) == r->data.amount );
+
+    case RULE_BYTES_GT:
+	return ( Ov_bytes( ov ) > r->data.amount );
+
+    case RULE_LINES_LT:
+	return ( Ov_lines( ov ) < r->data.amount );
+
+    case RULE_LINES_EQ:
+	return ( Ov_lines( ov ) == r->data.amount );
+
+    case RULE_LINES_GT:
+	return ( Ov_lines( ov ) > r->data.amount );
+
+    case RULE_MSGID:
+	return ( regexec( &r->data.regex, Ov_msgId( ov ), 0, NULL, 0 ) == 0 );
+
+    case RULE_NOREFS_LT:
+	ul = countRefs( Ov_ref( ov ) );
+	return ( ul < r->data.amount );
+
+    case RULE_NOREFS_EQ:
+	ul = countRefs( Ov_ref( ov ) );
+	return ( ul == r->data.amount );
+
+    case RULE_NOREFS_GT:
+	ul = countRefs( Ov_ref( ov ) );
+	return ( ul > r->data.amount );
+
+    case RULE_XPOSTS_LT:
+	if ( newsgroups == NULL )
+	    return FALSE;
+	ul = countGroups( newsgroups );
+	return ( ul < r->data.amount );
+
+    case RULE_XPOSTS_EQ:
+	if ( newsgroups == NULL )
+	    return FALSE;
+	ul = countGroups( newsgroups );
+	return ( ul == r->data.amount );
+
+    case RULE_XPOSTS_GT:
+	if ( newsgroups == NULL )
+	    return FALSE;
+	ul = countGroups( newsgroups );
+	return ( ul > r->data.amount );
+    }
+
+    ASSERT( FALSE );	/* Shouldn't get here */
+}
+
+/* Check a single filter to see if it fires. */
+static Bool
+checkFilter( const char *thisGrp, const char *newsgroups,
+	     const Over *ov, const Filter *f )
+{
+    int i;
+
+    for ( i = 0; i < f->nRules; i++ )
+	if ( ! checkRule( thisGrp, newsgroups, ov, &f->rules[i] ) )
+	     return FALSE;
+
+    return TRUE;
+}
+
+/* Add a filter to the list of filters. */
+void
+Flt_addFilter( const Filter *f )
+{
+    ASSERT( f != NULL );
+
+    if ( ( filter.nFilters + 1 ) > filter.maxFilters )
+    {
+	filter.filters =
+	    ( const Filter ** ) realloc( filter.filters,
+					 ( filter.maxFilters + 5 )
+					 * sizeof( Filter * ) );
+	if ( filter.filters == NULL )
+	{
+	    Log_err( "Could not realloc filter list" );
+	    exit( EXIT_FAILURE );
+	}
+	filter.maxFilters += 5;
+    }
+    filter.filters[ filter.nFilters++ ] = f;
+}
+
+/*
+ * Run the rules over the supplied overview. If a specific rule fires,
+ * returns its action. If no rule fires, return the default read mode.
+ */
+FilterAction
+Flt_checkFilters( const char *thisGrp, const char *newsgroups,
+		  const Over *ov, FetchMode mode )
+{
+    int i;
+
+    for ( i = 0; i < filter.nFilters; i++ )
+	if ( checkFilter( thisGrp, newsgroups, ov, filter.filters[ i ] ) )
+	{
+	    Log_dbg( "Filter %d fired on message %s", i, Ov_msgId( ov ) );
+	    return filter.filters[ i ]->action;
+	}
+
+    switch( mode )
+    {
+    case FULL:		return FILTER_FULL;
+    case THREAD:	return FILTER_THREAD;
+    case OVER:		return FILTER_XOVER;
+    }
+
+    ASSERT( FALSE );	/* Shouldn't get here */
+}
+
+Filter *
+new_Filter( void )
+{
+    Filter *f;
+
+    if ( ! ( f = ( Filter * ) malloc( sizeof( Filter ) ) ) )
+    {
+        Log_err( "Cannot allocate Filter" );
+        exit( EXIT_FAILURE );
+    }
+    f->nRules = 0;
+    f->maxRules = 0;
+    f->rules = NULL;
+    f->action = FILTER_FULL;
+    return f;
+}
+
+void
+del_Filter( Filter *f )
+{
+    if ( f == NULL )
+	return;
+
+    if ( f->rules != NULL )
+	free( f->rules );
+    free( f );    
+}
+
+FilterAction
+Flt_action( const Filter *f )
+{
+    return f->action;
+}
+
+int
+Flt_nRules( const Filter *f )
+{
+    return f->nRules;
+}
+
+/*
+ * Do we have a rule requiring us to fetch the Newsgroups: headers of
+ * articles?
+ */
+Bool
+Flt_getNewsgroups( void )
+{
+    return filter.needGroups;
+}
+
+FilterRule
+Flt_rule( const Filter *f, int ruleNo )
+{
+    ASSERT( ruleNo < f->nRules );
+    return f->rules[ ruleNo ];
+}
+
+void
+Flt_setAction( Filter *f, FilterAction action )
+{
+    f->action = action;
+}
+
+void
+Flt_addRule( Filter *f, FilterRule rule )
+{
+    /* Does the rule require Newsgroups: headers to be fetched? */
+    if ( rule.type == RULE_NEWSGROUP ||
+	 ( rule.type >= RULE_XPOSTS_LT && rule.type <= RULE_XPOSTS_GT ) )
+	filter.needGroups = TRUE;
+	
+    if ( f->nRules + 1 > f->maxRules )
+    {
+	f->rules =
+	    ( FilterRule * ) realloc( f->rules,
+				      ( f->maxRules + 5 )
+				      * sizeof( FilterRule ) );
+
+	if ( f->rules == NULL )
+	{
+	    Log_err( "Could not realloc rule list" );
+	    exit( EXIT_FAILURE );
+	}
+	f->maxRules += 5;
+    }
+    f->rules[ f->nRules++ ] = rule;
+}
+
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/filter.h	Wed Aug 09 22:19:17 2000 +0100
@@ -0,0 +1,95 @@
+/*
+  filter.h
+
+  Article filtering.
+
+  $Id: filter.h 189 2000-08-09 21:19:17Z bears $
+*/
+
+#ifndef	FILTER_H
+#define	FILTER_H
+
+#include <sys/types.h>
+#include <regex.h>
+#include "fetchlist.h"
+#include "over.h"
+
+/* The possible actions in a filter. */
+typedef enum {
+    FILTER_FULL,
+    FILTER_XOVER,
+    FILTER_THREAD,
+    FILTER_DISCARD
+} FilterAction;
+
+/* Representation of a rule. */
+typedef enum {
+    RULE_NEWSGROUP,					/* Wildmat data */
+    RULE_SUBJECT,					/* Regex data */
+    RULE_FROM,
+    RULE_MSGID,
+    RULE_BYTES_LT, RULE_BYTES_EQ, RULE_BYTES_GT,	/* Number data */
+    RULE_LINES_LT, RULE_LINES_EQ, RULE_LINES_GT,
+    RULE_NOREFS_LT, RULE_NOREFS_EQ, RULE_NOREFS_GT,
+    RULE_XPOSTS_LT, RULE_XPOSTS_EQ, RULE_XPOSTS_GT
+} FilterRuleType;
+
+typedef union {
+    regex_t regex;
+    unsigned long amount;
+    char *grp;
+} FilterRuleData;
+
+typedef struct {
+    FilterRuleType type;
+    FilterRuleData data;
+} FilterRule;
+
+/* A single filter is a collection of rules with an action. */
+typedef struct {
+    int nRules;
+    int maxRules;
+    FilterRule *rules;
+    FilterAction action;
+} Filter;
+
+/* Add a filter to the list of filters. */
+void
+Flt_addFilter( const Filter *f );
+
+/*
+ * Run the rules over the supplied overview. If a specific rule fires,
+ * returns its action. If no rule fires, return the default read mode.
+ */
+FilterAction
+Flt_checkFilters( const char *thisGrp, const char *newsgroups,
+		  const Over *ov, FetchMode mode );
+
+/*
+ * Build and access a filter
+ */
+Filter *
+new_Filter( void );
+
+void
+del_Filter( Filter *f );
+
+FilterAction
+Flt_action( const Filter *f );
+
+int
+Flt_nRules( const Filter *f );
+
+Bool
+Flt_getNewsgroups( void );
+
+FilterRule
+Flt_rule( const Filter *f, int ruleNo );
+
+void
+Flt_setAction( Filter *f, FilterAction action );
+
+void
+Flt_addRule( Filter *f, FilterRule rule );
+
+#endif	/* FILTER_H */