36 lines
1 KiB
Tcl
36 lines
1 KiB
Tcl
package require Tcl 8.6
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oo::class create StraddlingCheckerboardCypher {
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variable encmap decmap
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constructor table {
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# Sanity check the table
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foreach ch [lindex $table 0] i {"" 0 1 2 3 4 5 6 7 8 9} {
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if {$ch eq "" && $i ne "" && [lsearch -index 0 $table $i] < 1} {
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error "bad checkerboard table"
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}
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}
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# Synthesize the escaped number row
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foreach row $table {
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if {"/" ni $row} continue
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set pfx [lindex $row 0][expr {[lsearch -exact $row "/"]-1}]
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lappend table [list $pfx 0 1 2 3 4 5 6 7 8 9]
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break
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}
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# Build the actual per-character mapping
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foreach row $table {
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foreach ch [lrange $row 1 end] n {0 1 2 3 4 5 6 7 8 9} {
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if {$ch in {"" "/"}} continue; # Skip escape cases
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lappend encmap $ch [lindex $row 0]$n
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lappend decmap [lindex $row 0]$n $ch
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}
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}
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}
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# These methods just sanitize their input and apply the map
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method encode msg {
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string map $encmap [regsub -all {[^A-Z0-9.]} [string toupper $msg] ""]
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}
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method decode msg {
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string map $decmap [regsub -all {[^0-9]} $msg ""]
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}
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}
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