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# -*- tcl -*-
# # ## ### ##### ######## #############
# (C) 2009 Andreas Kupries
# @@ Meta Begin
# Package tcl::transform::limitsize 1
# Meta as::author {Andreas Kupries}
# Meta as::copyright 2009
# Meta as::license BSD
# Meta as::notes Possibilities for extension: Trigger the
# Meta as::notes EOF when finding specific patterns in
# Meta as::notes the input. Trigger the EOF based on some
# Meta as::notes external signal routed into the limiter.
# Meta as::notes Make the limit reconfigurable.
# Meta description Implementation of a transformation
# Meta description limiting the number of bytes read
# Meta description from its channel. An observer instead of
# Meta description a transformation, forcing an artificial
# Meta description EOF marker. Based on Tcl 8.6's
# Meta description transformation reflection support.
# Meta description Exports a single command adding a new
# Meta description transform of this type to a channel. One
# Meta description argument, the channel to extend, and the
# Meta description number of bytes to allowed to be read.
# Meta description No result.
# Meta platform tcl
# Meta require tcl::transform::core
# Meta require {Tcl 8.6}
# @@ Meta End
# This may help with things like zlib compression of messages. Have
# the message format a length at the front, followed by a payload of
# that size. Now we may compress messages. On the read side we can use
# the limiter to EOF on a message, then reset the limit for the
# next. This is a half-baked idea.
# # ## ### ##### ######## #############
package require Tcl 8.6
package require tcl::transform::core
# # ## ### ##### ######## #############
namespace eval ::tcl::transform {}
proc ::tcl::transform::limitsize {chan max} {
::chan push $chan [limitsize::implementation new $max]
}
oo::class create ::tcl::transform::limitsize::implementation {
superclass tcl::transform::core ;# -> initialize, finalize, destructor
method write {c data} {
return $data
}
method read {c data} {
# Reduce the limit of bytes allowed in the future according to
# the number of bytes we have seen already.
if {$max > 0} {
incr max -[string length $data]
if {$max < 0} {
set max 0
}
}
return $data
}
method limit? {c} {
return $max
}
# # ## ### ##### ######## #############
constructor {themax} {
set max $themax
return
}
variable max
# # ## ### ##### ######## #############
}
# # ## ### ##### ######## #############
package provide tcl::transform::limitsize 1
return
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