139 lines
5.3 KiB
Racket
139 lines
5.3 KiB
Racket
#lang scheme/base
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(require mzlib/foreign (only-in '#%foreign ffi-obj)) (unsafe!)
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(provide readline readline-bytes
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add-history add-history-bytes
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history-length history-get history-delete
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set-completion-function!
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readline-newline readline-redisplay)
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;; libncurses and/or libtermcap needed on some platforms
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(void (ffi-lib "libcurses" #:fail (lambda () #f)))
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(void (ffi-lib "libtermcap" #:fail (lambda () #f)))
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(define libreadline (ffi-lib "libreadline" '("5" "6" "4" "")))
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(define make-byte-string ; helper for the two types below
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(get-ffi-obj "scheme_make_byte_string" #f (_fun _pointer -> _scheme)))
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(define _bytes/eof/free ; register a finalizer on the resulting bytes
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(make-ctype _pointer
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(lambda (x) (and (not (eof-object? x)) x))
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(lambda (x)
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(if x
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(let ([b (make-byte-string x)])
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(register-finalizer b (lambda (_) (free x)))
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b)
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eof))))
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(define _string/eof/free ; make a Scheme str from C str & free immediately
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(make-ctype _pointer
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(lambda (x) (and (not (eof-object? x)) (string->bytes/utf-8 x)))
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(lambda (x)
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(if x
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(let ([s (bytes->string/utf-8 (make-byte-string x))]) (free x) s)
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eof))))
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(define readline
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(get-ffi-obj "readline" libreadline (_fun _string -> _string/eof/free)))
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(define readline-bytes
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(get-ffi-obj "readline" libreadline (_fun _bytes -> _bytes/eof/free)))
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(define add-history
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(get-ffi-obj "add_history" libreadline (_fun _string -> _void)))
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(define add-history-bytes
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(get-ffi-obj "add_history" libreadline (_fun _bytes -> _void)))
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(define history-length
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(let ([hl (ffi-obj #"history_length" libreadline)])
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(lambda () (ptr-ref hl _int))))
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(define history-base
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(let ([hb (ffi-obj #"history_base" libreadline)])
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(lambda () (ptr-ref hb _int))))
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;; The history library has this great feature: *some* function consume
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;; an index that is relative to history_base, and *some* get a plain
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;; offset. Someone just had so much fun they had to share. This
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;; deals with this absurdity, checks the range of the index, and deals
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;; with negative offsets.
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(define (hist-idx who idx base?)
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(let* ([len (history-length)]
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[idx (cond [(<= 0 idx (sub1 len)) idx]
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[(<= (- len) idx -1) (+ len idx)]
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[else (error who "index out of history range, -~a - ~a"
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len (sub1 len))])])
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(if base? (+ idx (history-base)) idx)))
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;; actually, returns a pointer to a struct with the string, but all we
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;; care about is the string...
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(define history-get
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(get-ffi-obj "history_get" libreadline
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(_fun (i) :: (_int = (hist-idx 'history-get i #t)) -> (_ptr o _string))))
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(define history-remove ; returns HIST_ENTRY* that history_free() frees
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(get-ffi-obj "remove_history" libreadline
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(_fun (i) :: (_int = (hist-idx 'history-delete i #f)) -> _pointer)))
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(define history-free ; ignore histdata_t return value
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(get-ffi-obj "free_history_entry" libreadline (_fun _pointer -> _void)
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;; if not available, use free
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(lambda () free)))
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(define (history-delete idx)
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(history-free (history-remove idx)))
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;; Simple completion: use this with a (string -> (list-of string)) function
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;; that returns the completions for a given string (can be used with other
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;; input string types too, depending on the `type' argument). Use #f to remove
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;; a completion function that was previously set.
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(define set-completion-function!
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(case-lambda
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[(func) (set-completion-function! func _string)]
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[(func type)
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(if func
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(set-ffi-obj! "rl_completion_entry_function" libreadline
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(_fun type _int -> _pointer)
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(completion-function func))
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(set-ffi-obj! "rl_completion_entry_function" libreadline _pointer #f))]))
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(define (completion-function func)
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(let ([cur '()])
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(define (complete str state)
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(if (zero? state)
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(begin (set! cur (func str)) (complete #f 1))
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(and (pair? cur)
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(let* ([cur (begin0 (car cur) (set! cur (cdr cur)))]
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[cur (if (string? cur) (string->bytes/utf-8 cur) cur)])
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(malloc (add1 (bytes-length cur)) cur 'raw)))))
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complete))
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(set-ffi-obj! "rl_readline_name" libreadline _bytes #"mzscheme")
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;; need to capture the real input port below
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(define real-input-port (current-input-port))
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(unless (eq? 'stdin (object-name real-input-port))
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(log-warning "mzrl warning: could not capture the real input port\n"))
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(unless (terminal-port? real-input-port)
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(log-warning "mzrl warning: input port is not a terminal\n"))
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;; We need to tell readline to pull content through our own function,
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;; to avoid buffering issues between C and Racket, and to allow
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;; racket threads to run while waiting for input.
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(set-ffi-obj! "rl_getc_function" libreadline (_fun _pointer -> _int)
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(lambda (_)
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(define next-byte (read-byte real-input-port))
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(if (eof-object? next-byte) -1 next-byte)))
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;; force cursor on a new line
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(define readline-newline
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(get-ffi-obj "rl_crlf" libreadline (_fun -> _void)
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(lambda ()
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(get-ffi-obj "rl_newline" libreadline (_fun -> _void)))))
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;; force redisplay of prompt and current user input
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(define readline-redisplay
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(get-ffi-obj "rl_forced_update_display" libreadline (_fun -> _void)))
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