74 lines
2.4 KiB
Racket
Executable File
74 lines
2.4 KiB
Racket
Executable File
#! /usr/bin/env /usr/local/bin/racket
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#lang racket
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;; default directory used for storing dynamic application data
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(define data-dir
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(build-path (find-system-path 'home-dir)
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(build-path ".local" "share" "palps")))
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(define (call-valid? call)
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(and
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(<= (string-length call) 9)
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(andmap
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(or/c char-numeric? char-alphabetic? (curry char=? #\-))
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(string->list call))))
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(define (our-make-temporary-file [copy-from #f])
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;; when deployed as a systemd socket, this program is expected to be
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;; ran with PrivateTmp. however, in case this is not true, we still
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;; make our own directory. "red", the restricted version of "ed",
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;; has no facility for getting outside of the directory we start it
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;; in.
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(make-temporary-file "red.~a"
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#:copy-from copy-from
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#:base-dir (make-temporary-directory)))
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;; unfortunately, we cannot just exec red and let it take over the
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;; I/O. ed, being the standard text editor, only works with standard
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;; line endings, \n. telnet and BPQ, however, use \r\n. \r\n upsets
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;; ed, the standard text editor. so we need to wrap the input and
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;; output ports ourselves in order to provide this translation.
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(define (ed [path (our-make-temporary-file)])
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(match-define
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(list stdout stdin pid stderr proc)
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(parameterize ([current-directory (path-only path)])
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(process* "/usr/bin/red"
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"-p*"
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(path->string (file-name-from-path path))
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#:set-pwd? #t)))
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(define buffer (make-bytes 128))
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(define (loop)
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(let ([evt-result
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(sync
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(choice-evt (read-bytes-avail!-evt buffer stdout)
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(read-line-evt (current-input-port) 'any)))])
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(cond
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;; read-line-evt results in a string. we have something to write
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;; on stdin.
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[(string? evt-result)
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(displayln evt-result stdin)
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(flush-output stdin)
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(loop)]
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;; read-bytes-avail!-evt results in an integer. we have
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;; something to read from stdout.
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[(integer? evt-result)
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(display (bytes->string/utf-8 (subbytes buffer 0 evt-result)))
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(flush-output)
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(loop)]
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;; either event may EOF, which means that ed has died.
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[(eof-object? evt-result)
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;; clean up
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(close-output-port stdin)
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(close-input-port stdout)
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(close-input-port stderr)
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(proc 'kill)
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path])))
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(loop))
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