57 lines
1.6 KiB
Scheme
57 lines
1.6 KiB
Scheme
(library
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(binary-format)
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(export size-type binary-format le32 le64 bytes)
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(import (rnrs)
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(list-utils))
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(define-syntax size-type
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(syntax-rules (le32 le64 bytes)
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((_ le32) 4)
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((_ le64) 8)
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((_ (bytes count)) count)))
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(define-syntax unpack-type
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(syntax-rules (le32 le64 bytes)
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((_ bv offset le32)
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(bytevector-u32-ref bv offset (endianness little)))
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((_ bv offset le64)
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(bytevector-u64-ref bv offset (endianness little)))
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((_ bv offset (bytes count))
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(let ((copy (make-bytevector count)))
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(bytevector-copy! bv offset copy 0 count)
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copy))))
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(define-syntax binary-format
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(syntax-rules ()
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((_ (name pack-name unpack-name) (field type) ...)
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(begin
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(define-record-type name (fields field ...))
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(define (unpack-name bv offset)
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(let ((offset offset))
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(define (inc-offset n v)
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(set! offset (+ offset n))
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v)
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((record-constructor (record-constructor-descriptor name))
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(inc-offset (size-type type) (unpack-type bv offset type)) ...)))))))
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;;; since le32, le64 and bytes are used as auxiliary keywords, we must export
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;;; definitions of them as well.
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;;; FIXME: use a macro to remove duplication
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(define-syntax le32
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(lambda (x)
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(syntax-violation 'le32 "misplaced auxiliary keyword" x)))
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(define-syntax le64
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(lambda (x)
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(syntax-violation 'le64 "misplaced auxiliary keyword" x)))
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(define-syntax bytes
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(lambda (x)
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(syntax-violation 'bytes "misplaced auxiliary keyword" x))))
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