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148c331769
* libguile/foreign.c (scm_pointer_to_scm, scm_scm_to_pointer): New
functions, useful to pass and receive SCM values to and from foreign
functions.
* module/system/foreign.scm: Export the new functions.
* doc/ref/api-foreign.texi (Foreign Variables): Add docs.
* test-suite/tests/foreign.test ("pointer<->scm"): Tests.
203 lines
6.7 KiB
Scheme
203 lines
6.7 KiB
Scheme
;;;; Copyright (C) 2010, 2011 Free Software Foundation, Inc.
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;;;;
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;;;; This library is free software; you can redistribute it and/or
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;;;; modify it under the terms of the GNU Lesser General Public
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;;;; License as published by the Free Software Foundation; either
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;;;; version 2.1 of the License, or (at your option) any later version.
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;;;;
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;;;; This library is distributed in the hope that it will be useful,
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;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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;;;; Lesser General Public License for more details.
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;;;;
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;;;; You should have received a copy of the GNU Lesser General Public
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;;;; License along with this library; if not, write to the Free Software
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;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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;;;;
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(define-module (system foreign)
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#:use-module (rnrs bytevectors)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-9)
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#:use-module (srfi srfi-9 gnu)
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#:export (void
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float double
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short
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unsigned-short
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int unsigned-int long unsigned-long size_t
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int8 uint8
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uint16 int16
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uint32 int32
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uint64 int64
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sizeof alignof
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%null-pointer
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null-pointer?
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pointer?
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make-pointer
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pointer->scm
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scm->pointer
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pointer-address
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pointer->bytevector
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bytevector->pointer
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set-pointer-finalizer!
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dereference-pointer
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string->pointer
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pointer->string
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pointer->procedure
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;; procedure->pointer (see below)
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make-c-struct parse-c-struct
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define-wrapped-pointer-type))
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(eval-when (load eval compile)
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(load-extension (string-append "libguile-" (effective-version))
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"scm_init_foreign"))
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;;;
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;;; Pointers.
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;;;
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(define (null-pointer? pointer)
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"Return true if POINTER is the null pointer."
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(= (pointer-address pointer) 0))
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(if (defined? 'procedure->pointer)
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(export procedure->pointer))
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;;;
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;;; Structures.
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;;;
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(define bytevector-pointer-ref
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(case (sizeof '*)
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((8) (lambda (bv offset)
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(make-pointer (bytevector-u64-native-ref bv offset))))
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((4) (lambda (bv offset)
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(make-pointer (bytevector-u32-native-ref bv offset))))
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(else (error "what machine is this?"))))
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(define bytevector-pointer-set!
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(case (sizeof '*)
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((8) (lambda (bv offset ptr)
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(bytevector-u64-native-set! bv offset (pointer-address ptr))))
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((4) (lambda (bv offset ptr)
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(bytevector-u32-native-set! bv offset (pointer-address ptr))))
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(else (error "what machine is this?"))))
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(define *writers*
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`((,float . ,bytevector-ieee-single-native-set!)
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(,double . ,bytevector-ieee-double-native-set!)
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(,int8 . ,bytevector-s8-set!)
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(,uint8 . ,bytevector-u8-set!)
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(,int16 . ,bytevector-s16-native-set!)
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(,uint16 . ,bytevector-u16-native-set!)
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(,int32 . ,bytevector-s32-native-set!)
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(,uint32 . ,bytevector-u32-native-set!)
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(,int64 . ,bytevector-s64-native-set!)
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(,uint64 . ,bytevector-u64-native-set!)
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(* . ,bytevector-pointer-set!)))
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(define *readers*
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`((,float . ,bytevector-ieee-single-native-ref)
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(,double . ,bytevector-ieee-double-native-ref)
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(,int8 . ,bytevector-s8-ref)
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(,uint8 . ,bytevector-u8-ref)
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(,int16 . ,bytevector-s16-native-ref)
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(,uint16 . ,bytevector-u16-native-ref)
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(,int32 . ,bytevector-s32-native-ref)
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(,uint32 . ,bytevector-u32-native-ref)
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(,int64 . ,bytevector-s64-native-ref)
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(,uint64 . ,bytevector-u64-native-ref)
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(* . ,bytevector-pointer-ref)))
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(define (align off alignment)
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(1+ (logior (1- off) (1- alignment))))
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(define (write-c-struct bv offset types vals)
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(let lp ((offset offset) (types types) (vals vals))
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(cond
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((not (pair? types))
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(or (null? vals)
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(error "too many values" vals)))
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((not (pair? vals))
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(error "too few values" types))
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(else
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;; alignof will error-check
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(let* ((type (car types))
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(offset (align offset (alignof type))))
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(if (pair? type)
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(write-c-struct bv offset (car types) (car vals))
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((assv-ref *writers* type) bv offset (car vals)))
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(lp (+ offset (sizeof type)) (cdr types) (cdr vals)))))))
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(define (read-c-struct bv offset types)
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(let lp ((offset offset) (types types) (vals '()))
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(cond
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((not (pair? types))
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(reverse vals))
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(else
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;; alignof will error-check
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(let* ((type (car types))
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(offset (align offset (alignof type))))
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(lp (+ offset (sizeof type)) (cdr types)
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(cons (if (pair? type)
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(read-c-struct bv offset (car types))
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((assv-ref *readers* type) bv offset))
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vals)))))))
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(define (make-c-struct types vals)
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(let ((bv (make-bytevector (sizeof types) 0)))
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(write-c-struct bv 0 types vals)
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(bytevector->pointer bv)))
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(define (parse-c-struct foreign types)
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(let ((size (fold (lambda (type total)
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(+ (sizeof type)
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(align total (alignof type))))
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0
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types)))
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(read-c-struct (pointer->bytevector foreign size) 0 types)))
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;;;
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;;; Wrapped pointer types.
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;;;
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(define-syntax define-wrapped-pointer-type
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(lambda (stx)
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"Define helper procedures to wrap pointer objects into Scheme
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objects with a disjoint type. Specifically, this macro defines PRED, a
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predicate for the new Scheme type, WRAP, a procedure that takes a
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pointer object and returns an object that satisfies PRED, and UNWRAP
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which does the reverse. PRINT must name a user-defined object printer."
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(syntax-case stx ()
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((_ type-name pred wrap unwrap print)
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(with-syntax ((%wrap (datum->syntax #'wrap (gensym "wrap"))))
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#'(begin
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(define-record-type type-name
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(%wrap pointer)
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pred
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(pointer unwrap))
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(define wrap
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;; Use a weak hash table to preserve pointer identity, i.e.,
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;; PTR1 == PTR2 <-> (eq? (wrap PTR1) (wrap PTR2)).
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(let ((ptr->obj (make-weak-value-hash-table 3000)))
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(lambda (ptr)
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;; XXX: We can't use `hash-create-handle!' +
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;; `set-cdr!' here because the former would create a
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;; weak-cdr pair but the latter wouldn't register a
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;; disappearing link (see `scm_hash_fn_set_x'.)
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(or (hash-ref ptr->obj ptr)
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(let ((o (%wrap ptr)))
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(hash-set! ptr->obj ptr o)
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o)))))
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(set-record-type-printer! type-name print)))))))
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