shareable-vectors.txt - clic - Clic is an command line interactive client for gopher written in Common LISP
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       shareable-vectors.txt (1537B)
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            1 
            2 # Shareable Byte Vectors
            3 
            4 Function: make-shareable-byte-vector size
            5 
            6 Create a vector of element type (UNSIGNED-BYTE 8) suitable for passing
            7 to WITH-POINTER-TO-VECTOR-DATA.
            8 
            9 ;; Minimal implementation:
           10 (defun make-shareable-byte-vector (size)
           11   (make-array size :element-type '(unsigned-byte 8)))
           12 
           13 
           14 Macro: with-pointer-to-vector-data (ptr-var vector) &body body
           15 
           16 Bind PTR-VAR to a pointer to the data contained in a shareable byte
           17 vector.
           18 
           19 VECTOR must be a shareable vector created by MAKE-SHAREABLE-BYTE-VECTOR.
           20 
           21 PTR-VAR may point directly into the Lisp vector data, or it may point
           22 to a temporary block of foreign memory which will be copied to and
           23 from VECTOR.
           24 
           25 Both the pointer object in PTR-VAR and the memory it points to have
           26 dynamic extent.  The results are undefined if foreign code attempts to
           27 access this memory outside this dynamic contour.
           28 
           29 The implementation must guarantee the memory pointed to by PTR-VAR
           30 will not be moved during the dynamic contour of this operator, either
           31 by creating the vector in a static area or temporarily disabling the
           32 garbage collector.
           33 
           34 ;; Minimal (copying) implementation:
           35 (defmacro with-pointer-to-vector-data ((ptr-var vector) &body body)
           36   (let ((vector-var (gensym))
           37         (size-var (gensym)))
           38     `(let* ((,vector-var ,vector)
           39             (,size-var (length ,vector-var)))
           40        (with-foreign-ptr (,ptr-var ,size-var)
           41          (mem-write-vector ,vector-var ,ptr :uint8)
           42          (prog1
           43              (progn ,@body)
           44            (mem-read-vector ,vector-var ,ptr-var :uint8 ,size-var))))))