scsh-0.6/scsh/syntax-helpers.scm

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;;; Macro expanding procs for scsh.
;;; Written for Clinger/Rees explicit renaming macros.
;;; Needs name-export and receive-syntax S48 packages.
;;; Also needs scsh's utilities package (for CHECK-ARG).
;;; Must be loaded into for-syntax package.
;;; Copyright (c) 1993 by Olin Shivers.
(define-syntax define-simple-syntax
(syntax-rules ()
((define-simple-syntax (name . pattern) result)
(define-syntax name (syntax-rules () ((name . pattern) result))))))
(define (name? thing)
(or (symbol? thing)
(generated? thing)))
;;; Debugging macro:
(define-simple-syntax (assert exp)
(if (not exp) (error "Assertion failed" (quote exp))))
;;; Some process forms and redirections are implicitly backquoted.
(define (backq form rename)
(list (rename 'quasiquote) form)) ; form -> `form
(define (unq form rename)
(list (rename 'unquote) form)) ; form -> ,form
(define (make-backquoter rename)
(lambda (form) (list (rename 'quasiquote) form)))
(define (make-unquoter rename)
(lambda (form) (list (rename 'unquote) form)))
;; DEBLOCK maps an expression to a list of expressions, flattening BEGINS.
;; (deblock '(begin (begin 3 4) 5 6 (begin 7 8))) => (3 4 5 6 7 8)
(define (deblock exp rename compare)
(let ((%block (rename 'begin)))
(let deblock1 ((exp exp))
(if (and (pair? exp)
(name? (car exp))
(compare %block (car exp)))
(apply append (map deblock1 (cdr exp)))
(list exp)))))
;; BLOCKIFY maps an expression list to a BEGIN form, flattening nested BEGINS.
;; (blockify '( (begin 3 4) 5 (begin 6) )) => (begin 3 4 5 6)
(define (blockify exps rename compare)
(let ((new-exps (apply append
(map (lambda (exp) (deblock exp rename compare))
exps))))
(cond ((null? new-exps)
(error "Empty BEGIN" exps))
((null? (cdr new-exps)) ; (begin exp) => exp
(car new-exps))
(else `(,(rename 'begin) . ,new-exps)))))
(define (thunkate code rename compare)
(let ((%lambda (rename 'lambda)))
`(,%lambda () ,@(deblock code rename compare))))
;;; Process forms are rewritten into code that causes them to execute
;;; in the current process.
;;; (BEGIN . scheme-code) => (STDIO->STDPORTS (LAMBDA () . scheme-code))
;;; (| pf1 pf2) => (BEGIN (FORK/PIPE (LAMBDA () pf1-code))
;;; pf2-code)
;;; (|+ conns pf1 pf2) => (BEGIN
;;; (FORK/PIPE+ `conns (LAMBDA () pf1-code))
;;; pf2-code)
;;; (epf . epf) => epf-code
;;; (prog arg1 ... argn) => (APPLY EXEC-PATH `(prog arg1 ... argn))
;;; [note the implicit backquoting of PROG, ARG1, ...]
;;; NOTE: | and |+ won't read into many Scheme's as a symbol. If your
;;; Scheme doesn't handle it, kill them, and just use the PIPE, PIPE+
;;; aliases.
(define (transcribe-process-form pf rename compare)
(if (and (list? pf) (pair? pf))
(let ((head (car pf)))
(cond
((compare head (rename 'begin))
(transcribe-begin-process-form (cdr pf) rename compare))
((compare head (rename 'epf))
(transcribe-extended-process-form (cdr pf) rename compare))
((compare head (rename 'pipe))
(transcribe-simple-pipeline (cdr pf) rename compare))
((compare head (rename '|))
(transcribe-simple-pipeline (cdr pf) rename compare))
((compare head (rename '|+))
(let ((conns (backq (cadr pf) rename))
(pfs (cddr pf)))
(transcribe-complex-pipeline conns pfs rename compare)))
((compare head (rename 'pipe+))
(let ((conns (backq (cadr pf) rename))
(pfs (cddr pf)))
(transcribe-complex-pipeline conns pfs rename compare)))
(else (let ((%apply (rename 'apply))
(%exec-path (rename 'exec-path))
(pf (backq pf rename)))
`(,%apply ,%exec-path ,pf)))))
(error "Illegal process form" pf)))
(define (transcribe-begin-process-form body rename compare)
(let ((%with-stdio-ports* (rename 'with-stdio-ports*))
(%lambda (rename 'lambda)))
`(,%with-stdio-ports* (,%lambda () . ,body))))
(define (transcribe-simple-pipeline pfs rename compare)
(if (null? pfs) (error "Empty pipeline")
(let* ((%fork/pipe (rename 'fork/pipe))
(trans-pf (lambda (pf)
(transcribe-process-form pf rename compare)))
(chunks (reverse (map trans-pf pfs)))
(last-chunk (car chunks))
(first-chunks (reverse (cdr chunks)))
(forkers (map (lambda (chunk)
`(,%fork/pipe ,(thunkate chunk rename compare)))
first-chunks)))
(blockify `(,@forkers ,last-chunk) rename compare))))
;;; Should let-bind CONNS in case it's a computed form.
(define (transcribe-complex-pipeline conns pfs rename compare)
(if (null? pfs) (error "Empty pipeline")
(let* ((%fork/pipe+ (rename 'fork/pipe+))
(trans-pf (lambda (pf)
(transcribe-process-form pf rename compare)))
(chunks (reverse (map trans-pf pfs)))
(last-chunk (car chunks))
(first-chunks (reverse (cdr chunks)))
(forkers (map (lambda (chunk)
`(,%fork/pipe+ ,conns
,(thunkate chunk rename compare)))
first-chunks)))
(blockify `(,@forkers ,last-chunk) rename compare))))
(define (transcribe-extended-process-form epf rename compare)
(let* ((pf (car epf)) ; First form is the process form.
(redirs (cdr epf)) ; Others are redirection forms.
(trans-redir (lambda (r) (transcribe-redirection r rename compare)))
(redir-chunks (map trans-redir redirs))
(pf-chunk (transcribe-process-form pf rename compare)))
(blockify `(,@redir-chunks ,pf-chunk) rename compare)))
(define (transcribe-redirection redir rename compare)
(let* ((backq (make-backquoter rename))
(parse-spec (lambda (x default-fdes) ; Parse an ([fdes] arg) form.
;; X must be a list of 1 or 2 elts.
(check-arg (lambda (x) (and (list? x)
(< 0 (length x) 3)))
x transcribe-redirection)
(let ((a (car x))
(b (cdr x)))
(if (null? b) (values default-fdes (backq a))
(values (backq a) (backq (car b)))))))
(oops (lambda () (error "unknown i/o redirection" redir)))
(%open (rename 'shell-open))
; (%dup-port (rename 'dup-port))
(%dup->fdes (rename 'dup->fdes))
; (%run/port (rename 'run/port))
(%open-string-source (rename 'open-string-source))
(%open/create+trunc (rename 'open/create+trunc))
(%open/write+append+create (rename 'open/write+append+create))
(%q (lambda (x) (list (rename 'quote) x)))
(%close (rename 'close))
(%move->fdes (rename 'move->fdes))
(%set! (rename 'set!))
(%<<-port-holder (rename '<<-port-holder))
(%let (rename 'let))
(%port (rename 'port))
(%stdports->stdio (rename 'stdports->stdio)))
(cond ((pair? redir)
(let ((args (cdr redir))
(op (car redir)))
(cond
((compare op (rename '<))
(receive (fdes fname) (parse-spec args 0)
`(,%open ,fname 0 ,fdes)))
((compare op (rename '>))
(receive (fdes fname) (parse-spec args 1)
`(,%open ,fname ,%open/create+trunc ,fdes)))
;;; BUG BUG -- EPF is backquoted by parse-spec.
; ((<<<) ; Just a RUN/PORT with a specific target fdes.
; (receive (fdes epf) (parse-spec args 0)
; `(,%dup-port (,%run/port . ,epf) ,fdes))) ; Add a WITH-PORT.
;; We save the port in the global variable <<-port-holder to prevent a
;; GC from closing the port before the exec().
((compare op (rename '<<))
(receive (fdes exp) (parse-spec args 0)
`(,%let ((,%port (,%open-string-source ,exp)))
(,%set! ,%<<-port-holder ,%port)
(,%move->fdes ,%port ,fdes))))
((compare op (rename '>>))
(receive (fdes fname) (parse-spec args 1)
`(,%open ,fname ,%open/write+append+create ,fdes)))
((compare op (rename '=))
(assert (= 2 (length args))) ; Syntax check.
`(,%dup->fdes ,(backq (cadr args)) ,(backq (car args))))
((compare op (rename '-)) ; (- fdes) => close the fdes.
(assert (= 1 (length args))) ; Syntax check.
`(,%close ,(backq (car args))))
(else (oops)))))
((compare redir (rename 'stdports))
`(,%stdports->stdio))
(else (oops)))))
;;; <<< should be {