Paste: Simple mmap counter

USING: alien.c-types arrays command-line io io.encodings.binary
io.files io.files.temp io.mmap kernel math math.order math.parser
memoize namespaces sequences specialized-arrays system ;
IN: mmap-count

SPECIALIZED-ARRAY: int

MEMO: mmap-count-path ( -- path ) "counts" temp-file ;
CONSTANT: num-counters 10

: ensure-counts-file ( -- )
    mmap-count-path exists? [
        num-counters <int-array>
        mmap-count-path binary set-file-contents
    ] unless ;

: increment-at ( n -- )
    mmap-count-path int [
        [ [ 1 + ] change-nth ]
        [ nth number>string print ] 2bi
    ] with-mapped-array ;

: check-args ( -- )
    command-line get
    [ length 1 = ] [ first string>number f = not ] bi
    [ t = ] both? [ "Usage: mmap-count <n>" print 1 exit ] unless ;

: exit-out-of-bounds ( n -- )
    number>string write " not in counter range [0," num-counters 1 -
    number>string "]" 3array "" join print 1 exit ;

: handle-command ( -- )
    check-args command-line get first string>number
    dup 0 num-counters 1 - between?
    [ ensure-counts-file increment-at ] [ exit-out-of-bounds ] if ;

MAIN: handle-command