Index: lib/xvfs/xvfs.tcl
==================================================================
--- lib/xvfs/xvfs.tcl
+++ lib/xvfs/xvfs.tcl
@@ -97,16 +97,20 @@
 	array set fileInfo $fileInfoDict
 
 	switch -exact -- $fileInfo(type) {
 		"file" {
 			set type "XVFS_FILE_TYPE_REG"
-			set fd [open $inputFile]
-			fconfigure $fd -encoding binary -translation binary -blocking true
-			set data [read $fd]
+			if {[info exists fileInfo(fileContents)]} {
+				set data $fileInfo(fileContents)
+			} else {
+				set fd [open $inputFile]
+				fconfigure $fd -encoding binary -translation binary -blocking true
+				set data [read $fd]
+				close $fd
+			}
 			set size [string length $data]
 			set data [string trimleft [binaryToCHex $data "\t\t\t"]]
-			close $fd
 		}
 		"directory" {
 			set type "XVFS_FILE_TYPE_DIR"
 			set children $fileInfo(children)
 			set size [llength $children]
@@ -203,10 +207,14 @@
 
 	processFile $fsName $inputFile $outputFile [array get fileInfo]
 	lappend outputFiles $outputFile
 
 	if {$isTopLevel} {
+		if {[info command ::xvfs::callback::addOutputFiles] ne ""} {
+			lappend outputFiles {*}[::xvfs::callback::addOutputFiles]
+		}
+
 		::xvfs::_emitLine "\};"
 	}
 
 	return $outputFiles
 }