67 lines
2.0 KiB
Scheme
67 lines
2.0 KiB
Scheme
(define-module (scmvm assembler)
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#:use-module (srfi srfi-1)
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#:use-module (scmvm vm)
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#:use-module (rnrs bytevectors)
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#:use-module (rnrs io ports)
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#:use-module ((scheme base)
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#:select (write-u8 write-bytevector))
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#:export (assemble assemble-file))
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(define (lookup-instruction inst)
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(define inst-obj (assq inst *instruction-set*))
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(if inst-obj
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inst-obj
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(error (format #f "could not find instruction ~a" inst))))
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(define label? (compose not pair?))
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(define (variable? x)
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(and (pair? x) (eq? (car x) 'variable)))
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(define (instruction? x)
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(and (not (label? x))
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(not (variable? x))))
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(define (find-labels inst-seq n)
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(cond
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[(null? inst-seq) '()]
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[(label? (car inst-seq))
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(acons (car inst-seq) n (find-labels (cdr inst-seq) n))]
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[(variable? (car inst-seq))
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(acons (cadar inst-seq) n (find-labels (cdr inst-seq) (+ n 4)))]
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[else
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(find-labels (cdr inst-seq) (if (eq? (caar inst-seq) 'push) (+ n 5) (+ n 1)))]))
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(define (write-word word)
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(define bv (make-bytevector 4))
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(bytevector-s32-native-set! bv 0 word)
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(write-bytevector bv))
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(define (assemble inst-seq port)
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(with-output-to-port port
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(lambda ()
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(define labels (find-labels inst-seq 1))
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(let loop ([seq inst-seq])
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(cond
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[(null? seq) '()]
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[(label? (car seq)) (loop (cdr seq))]
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[(variable? (car seq))
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(write-word (caddar seq))
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(loop (cdr seq))]
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[else
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(let* [(inst (car seq))
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(inst-obj (lookup-instruction (car inst)))]
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(write-u8 (instruction-code inst-obj))
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(when (eq? (car inst) 'push)
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(if (number? (cadr inst))
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(write-word (cadr inst))
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(write-word (assq-ref labels (cadr inst)))))
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(loop (cdr seq)))])))))
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(define (assemble-file file out)
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(call-with-input-file file
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(lambda (in)
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(define (read-all next)
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(if (eof-object? next)
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'()
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(cons next (read-all (read in)))))
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(assemble (read-all (read in)) out))))
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