--- doc/chan.n.orig	2006-10-28 22:37:48.000000000 -0600
+++ doc/chan.n	2006-11-21 22:47:33.000000000 -0700
@@ -493,6 +493,16 @@
 only those channel names that match it (according to the rules of
 \fBstring match\fR) will be returned.
 .TP
+\fBchan pending \fImode channelId\fR
+.
+Depending on whether \fImode\fr is "input" or "output", returns the number of 
+bytes of input or output (respectively) currently buffered 
+internally for \fIchannelId\fr (especially useful in a readable event 
+callback to impose application-specific limits on input line lengths to avoid
+a potential denial-of-service attack where a hostile user crafts
+an extremely long line that exceeds the available memory to buffer it).
+Returns -1 if the channel was not opened for the mode in question.
+.TP
 \fBchan postevent \fIchannelId eventSpec\fR
 .
 This subcommand is used by command handlers specified with \fBchan
--- generic/tclBasic.c.orig	2006-10-28 21:55:59.000000000 -0600
+++ generic/tclBasic.c	2006-11-21 19:01:59.000000000 -0700
@@ -485,6 +485,10 @@
     Tcl_CreateObjCommand(interp, "::tcl::chan::rPostevent",
 	    TclChanPostEventObjCmd, (ClientData) NULL, NULL);
 
+    /* TIP #287 */
+    Tcl_CreateObjCommand(interp, "::tcl::chan::Pending",
+	    TclChanPendingObjCmd, (ClientData) NULL, NULL);
+
     /*
      * Register the built-in functions. This is empty now that they are
      * implemented as commands in the ::tcl::mathfunc namespace.
--- generic/tclInt.h.orig	2006-10-28 22:08:38.000000000 -0600
+++ generic/tclInt.h	2006-11-21 18:31:37.000000000 -0700
@@ -2286,6 +2286,9 @@
 MODULE_SCOPE int	Tcl_CdObjCmd(ClientData clientData,
 			    Tcl_Interp *interp, int objc,
 			    Tcl_Obj *CONST objv[]);
+MODULE_SCOPE int	TclChanPendingObjCmd(
+			    ClientData clientData, Tcl_Interp *interp,
+			    int objc, Tcl_Obj *CONST objv[]); /* TIP 287 */
 MODULE_SCOPE int	TclChanTruncateObjCmd(
 			    ClientData clientData, Tcl_Interp *interp,
 			    int objc, Tcl_Obj *CONST objv[]);
--- generic/tclIOCmd.c.orig	2006-10-28 21:58:27.000000000 -0600
+++ generic/tclIOCmd.c	2006-11-21 22:51:36.000000000 -0700
@@ -1619,6 +1619,74 @@
 }
 
 /*
+ *---------------------------------------------------------------------------
+ *
+ * TclChanPendingObjCmd --
+ *
+ *	This function is invoked to process the Tcl "chan pending" 
+ *	command (TIP #287). See the user documentation for details on 
+ *	what it does.
+ *
+ * Results:
+ *	A standard Tcl result.
+ *
+ * Side effects:
+ *	Sets interp's result to the number of bytes of buffered input or
+ *	output (depending on whether the first argument is "input" or
+ *	"output"), or -1 if the channel wasn't opened for that mode.
+ *
+ *---------------------------------------------------------------------------
+ */
+
+	/* ARGSUSED */
+int
+TclChanPendingObjCmd(
+    ClientData unused,		/* Not used. */
+    Tcl_Interp *interp,		/* Current interpreter. */
+    int objc,			/* Number of arguments. */
+    Tcl_Obj *CONST objv[])	/* Argument objects. */
+{
+    Tcl_Channel chan;
+    int index, mode;
+    char *arg;
+    static CONST char *options[] = {"input", "output", (char *) NULL};
+    enum options {PENDING_INPUT, PENDING_OUTPUT};
+
+    if (objc != 3) {
+	Tcl_WrongNumArgs(interp, 1, objv, "mode channelId");
+	return TCL_ERROR;
+    }
+
+    if (Tcl_GetIndexFromObj(interp, objv[1], options, "mode", 0, 
+	    &index) != TCL_OK) {
+	return TCL_ERROR;
+    }
+
+    arg = Tcl_GetString(objv[2]);
+    chan = Tcl_GetChannel(interp, arg, &mode);
+    if (chan == NULL) {
+	return TCL_ERROR;
+    }
+
+    switch ((enum options) index) {
+    case PENDING_INPUT:
+	if ((mode & TCL_READABLE) == 0) {
+	    Tcl_SetObjResult(interp, Tcl_NewIntObj(-1));
+	} else {
+	    Tcl_SetObjResult(interp, Tcl_NewIntObj(Tcl_InputBuffered(chan)));
+	}
+	return TCL_OK;
+    case PENDING_OUTPUT:
+	if ((mode & TCL_WRITABLE) == 0) {
+	    Tcl_SetObjResult(interp, Tcl_NewIntObj(-1));
+	} else {
+	    Tcl_SetObjResult(interp, Tcl_NewIntObj(Tcl_OutputBuffered(chan)));
+	}
+	return TCL_OK;
+    }
+}
+
+/*
  *----------------------------------------------------------------------
  *
  * Tcl_ChanTruncateObjCmd --
--- library/init.tcl.orig	2006-09-22 12:13:29.000000000 -0600
+++ library/init.tcl	2006-11-21 19:03:59.000000000 -0700
@@ -78,7 +78,9 @@
     # Set up the 'chan' ensemble (TIP #208).
     namespace eval chan {
         # TIP #219. Added methods: create, postevent.
+        # TIP #287. Added method: pending.
         namespace ensemble create -command ::chan -map {
+            pending     ::tcl::chan::Pending
             blocked     ::fblocked
             close       ::close
             configure   ::fconfigure
--- tests/chan.test.orig	2006-10-29 13:59:35.000000000 -0700
+++ tests/chan.test	2006-11-21 22:35:24.000000000 -0700
@@ -24,7 +24,7 @@
 } -returnCodes error -result "wrong # args: should be \"chan subcommand ?argument ...?\""
 test chan-1.2 {chan command general syntax} -body {
     chan FOOBAR
-} -returnCodes error -result "unknown or ambiguous subcommand \"FOOBAR\": must be blocked, close, configure, copy, create, eof, event, flush, gets, names, postevent, puts, read, seek, tell, or truncate"
+} -returnCodes error -result "unknown or ambiguous subcommand \"FOOBAR\": must be blocked, close, configure, copy, create, eof, event, flush, gets, names, pending, postevent, puts, read, seek, tell, or truncate"
 
 test chan-2.1 {chan command: blocked subcommand} -body {
     chan blocked foo bar
@@ -96,6 +96,116 @@
     catch {removeFile $file}
 }
 
+# TIP 287: chan pending
+test chan-16.1 {chan command: pending subcommand} -body {
+    chan pending
+} -returnCodes error -result "wrong # args: should be \"chan pending mode channelId\""
+test chan-16.2 {chan command: pending subcommand} -body {
+    chan pending stdin
+} -returnCodes error -result "wrong # args: should be \"chan pending mode channelId\""
+test chan-16.3 {chan command: pending subcommand} -body {
+    chan pending stdin stdout stderr
+} -returnCodes error -result "wrong # args: should be \"chan pending mode channelId\""
+test chan-16.4 {chan command: pending subcommand} -body {
+    chan pending {input output} stdout
+} -returnCodes error -result "bad mode \"input output\": must be input or output"
+test chan-16.5 {chan command: pending input subcommand} -body {
+    chan pending input stdout 
+} -result -1
+test chan-16.6 {chan command: pending input subcommand} -body {
+    chan pending input stdin
+} -result 0
+test chan-16.7 {chan command: pending input subcommand} -body {
+    chan pending input FOOBAR
+} -returnCodes error -result "can not find channel named \"FOOBAR\""
+test chan-16.8 {chan command: pending input subcommand} -setup {
+    set file [makeFile {} testAvailable]
+    set f [open $file w+]
+    chan configure $f -translation lf -buffering line
+} -body {
+    chan puts $f foo
+    chan puts $f bar
+    chan puts $f baz
+    chan seek $f 0
+    chan gets $f
+    chan pending input $f
+} -result 8 -cleanup {
+    catch {chan close $f}
+    catch {removeFile $file}
+}
+test chan-16.9 {chan command: pending input subcommand} -setup {
+    proc chan-16.9-accept {sock addr port} {
+        chan configure $sock -blocking 0 -buffering line -buffersize 32
+        chan event $sock readable [list chan-16.9-readable $sock]
+    }
+
+    proc chan-16.9-readable {sock} {
+        set r [chan gets $sock line]
+        set l [string length $line]
+        set e [chan eof $sock]
+        set b [chan blocked $sock]
+        set i [chan pending input $sock]
+
+        lappend ::chan-16.9-data $r $l $e $b $i
+
+        if {$r != -1 || $e || $l || !$b || $i > 128} {
+            set data [read $sock $i]
+            lappend ::chan-16.9-data [string range $data 0 2]
+            lappend ::chan-16.9-data [string range $data end-2 end]
+            set ::chan-16.9-done 1
+        }
+    }
+
+    proc chan-16.9-client {} {
+        chan puts -nonewline $::client ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890
+        chan flush $::client
+        after 100 chan-16.9-client
+    }
+
+    set ::server [socket -server chan-16.9-accept -myaddr 127.0.0.1 0]
+    set ::client [socket 127.0.0.1 [lindex [fconfigure $::server -sockname] 2]]
+    set ::chan-16.9-data [list]
+    set ::chan-16.9-done 0
+} -body {
+    after idle chan-16.9-client 
+    vwait ::chan-16.9-done
+    set ::chan-16.9-data
+} -result {-1 0 0 1 36 -1 0 0 1 72 -1 0 0 1 108 -1 0 0 1 144 ABC 890} -cleanup {
+    catch {chan close $client}
+    catch {chan close $server}
+    rename chan-16.9-accept {}
+    rename chan-16.9-readable {}
+    rename chan-16.9-client {}
+    unset -nocomplain ::chan-16.9-data
+    unset -nocomplain ::chan-16.9-done
+    unset -nocomplain ::server
+    unset -nocomplain ::client
+}
+test chan-16.10 {chan command: pending output subcommand} -body {
+    chan pending output stdin
+} -result -1
+test chan-16.11 {chan command: pending output subcommand} -body {
+    chan pending output stdout
+} -result 0
+test chan-16.12 {chan command: pending output subcommand} -body {
+    chan pending output FOOBAR
+} -returnCodes error -result "can not find channel named \"FOOBAR\""
+test chan-16.13 {chan command: pending output subcommand} -setup {
+    set file [makeFile {} testPendingOutput]
+    set f [open $file w+]
+    chan configure $f -translation lf -buffering full -buffersize 1024
+} -body {
+    set result [list]
+    chan puts $f [string repeat x 512]
+    lappend result [chan pending output $f]
+    chan flush $f
+    lappend result [chan pending output $f]
+} -result [list 513 0] -cleanup {
+    unset -nocomplain result
+    catch {chan close $f}
+    catch {removeFile $file}
+}
+
 cleanupTests
 return
 
--- tests/ioCmd.test.orig	2006-10-28 23:06:44.000000000 -0600
+++ tests/ioCmd.test	2006-11-21 19:29:42.000000000 -0700
@@ -628,7 +628,7 @@
 test iocmd-20.1 {chan, unknown method} {
     catch {chan foo} msg
     set msg
-} {unknown or ambiguous subcommand "foo": must be blocked, close, configure, copy, create, eof, event, flush, gets, names, postevent, puts, read, seek, tell, or truncate}
+} {unknown or ambiguous subcommand "foo": must be blocked, close, configure, copy, create, eof, event, flush, gets, names, pending, postevent, puts, read, seek, tell, or truncate}
 
 # --- --- --- --------- --------- ---------
 # chan create, and method "initalize"
