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# queue.tcl --
#
# Queue implementation for Tcl.
#
# Copyright (c) 1998-2000 by Ajuba Solutions.
# Copyright (c) 2008-2010 Andreas Kupries
#
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
#
# RCS: @(#) $Id: queue_oo.tcl,v 1.2 2010/09/10 17:31:04 andreas_kupries Exp $
package require Tcl 8.5
package require TclOO 0.6.1- ; # This includes 1 and higher.
# Cleanup first
catch {namespace delete ::struct::queue::queue_oo}
catch {rename ::struct::queue::queue_oo {}}
oo::class create ::struct::queue::queue_oo {
variable qat qret qadd
# variable qat - Index in qret of next element to return
# variable qret - List of elements waiting for return
# variable qadd - List of elements added and not yet reached for return.
constructor {} {
set qat 0
set qret [list]
set qadd [list]
return
}
# clear --
#
# Clear a queue.
#
# Results:
# None.
method clear {} {
set qat 0
set qret [list]
set qadd [list]
return
}
# get --
#
# Get an item from a queue.
#
# Arguments:
# count number of items to get; defaults to 1
#
# Results:
# item first count items from the queue; if there are not enough
# items in the queue, throws an error.
method get {{count 1}} {
if { $count < 1 } {
return -code error "invalid item count $count"
} elseif { $count > [my size] } {
return -code error "insufficient items in queue to fill request"
}
my Shift?
if { $count == 1 } {
# Handle this as a special case, so single item gets aren't
# listified
set item [lindex $qret $qat]
incr qat
my Shift?
return $item
}
# Otherwise, return a list of items
if {$count > ([llength $qret] - $qat)} {
# Need all of qret (from qat on) and parts of qadd, maybe all.
set max [expr {$qat + $count - 1 - [llength $qret]}]
set result [concat [lrange $qret $qat end] [lrange $qadd 0 $max]]
my Shift
set qat $max
} else {
# Request can be satisified from qret alone.
set max [expr {$qat + $count - 1}]
set result [lrange $qret $qat $max]
set qat $max
}
incr qat
my Shift?
return $result
}
# peek --
#
# Retrieve the value of an item on the queue without removing it.
#
# Arguments:
# count number of items to peek; defaults to 1
#
# Results:
# items top count items from the queue; if there are not enough items
# to fulfill the request, throws an error.
method peek {{count 1}} {
variable queues
if { $count < 1 } {
return -code error "invalid item count $count"
} elseif { $count > [my size] } {
return -code error "insufficient items in queue to fill request"
}
my Shift?
if { $count == 1 } {
# Handle this as a special case, so single item pops aren't
# listified
return [lindex $qret $qat]
}
# Otherwise, return a list of items
if {$count > [llength $qret] - $qat} {
# Need all of qret (from qat on) and parts of qadd, maybe all.
set over [expr {$qat + $count - 1 - [llength $qret]}]
return [concat [lrange $qret $qat end] [lrange $qadd 0 $over]]
} else {
# Request can be satisified from qret alone.
return [lrange $qret $qat [expr {$qat + $count - 1}]]
}
}
# put --
#
# Put an item into a queue.
#
# Arguments:
# args items to put.
#
# Results:
# None.
method put {args} {
if {![llength $args]} {
return -code error "wrong # args: should be \"[self] put item ?item ...?\""
}
foreach item $args {
lappend qadd $item
}
return
}
# unget --
#
# Put an item into a queue. At the _front_!
#
# Arguments:
# item item to put at the front of the queue
#
# Results:
# None.
method unget {item} {
if {![llength $qret]} {
set qret [list $item]
} elseif {$qat == 0} {
set qret [linsert [my K $qret [unset qret]] 0 $item]
} else {
# step back and modify return buffer
incr qat -1
set qret [lreplace [my K $qret [unset qret]] $qat $qat $item]
}
return
}
# size --
#
# Return the number of objects on a queue.
#
# Results:
# count number of items on the queue.
method size {} {
return [expr {
[llength $qret] + [llength $qadd] - $qat
}]
}
# ### ### ### ######### ######### #########
method Shift? {} {
if {$qat < [llength $qret]} return
# inlined Shift
set qat 0
set qret $qadd
set qadd [list]
return
}
method Shift {} {
set qat 0
set qret $qadd
set qadd [list]
return
}
method K {x y} { set x }
}
# ### ### ### ######### ######### #########
## Ready
namespace eval ::struct {
# Get 'queue::queue' into the general structure namespace for
# pickup by the main management.
proc queue_tcl {args} {
if {[llength $args]} {
uplevel 1 [::list ::struct::queue::queue_oo create {*}$args]
} else {
uplevel 1 [::list ::struct::queue::queue_oo new]
}
}
}
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