src/code/target-c-call.lisp

   1 ;;;; FIXME: This file and host-c-call.lisp are separate from the
   2 ;;;; rest of the alien source code for historical reasons: CMU CL
   3 ;;;; made a distinction between the stuff in the C-CALL package and
   4 ;;;; stuff in the ALIEN package. There's no obvious boundary
   5 ;;;; there, though, and SBCL doesn't try to make this distinction,
   6 ;;;; so it might make sense to just merge these files in with the
   7 ;;;; rest of the SB-ALIEN code.
   8
   9 ;;;; This software is part of the SBCL system. See the README file for
  10 ;;;; more information.
  11 ;;;;
  12 ;;;; This software is derived from the CMU CL system, which was
  13 ;;;; written at Carnegie Mellon University and released into the
  14 ;;;; public domain. The software is in the public domain and is
  15 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  16 ;;;; files for more information.
  17
  18 (in-package "SB-ALIEN")
  19 \f
  20 ;;;; extra types
  21
  22 (define-alien-type char (integer 8))
  23 (define-alien-type short (integer 16))
  24 (define-alien-type int (integer 32))
  25 #-(and win32 x86-64)
  26 (define-alien-type long (integer #.sb-vm:n-machine-word-bits))
  27 #+(and win32 x86-64)
  28 (define-alien-type long (integer 32))
  29
  30 (define-alien-type long-long (integer 64))
  31
  32 (define-alien-type unsigned-char (unsigned 8))
  33 (define-alien-type unsigned-short (unsigned 16))
  34 (define-alien-type unsigned-int (unsigned 32))
  35 #-(and win32 x86-64)
  36 (define-alien-type unsigned-long (unsigned #.sb-vm:n-machine-word-bits))
  37 #+(and win32 x86-64)
  38 (define-alien-type unsigned-long (unsigned 32))
  39 (define-alien-type unsigned-long-long (unsigned 64))
  40
  41 (define-alien-type float single-float)
  42 (define-alien-type double double-float)
  43
  44 (define-alien-type utf8-string (c-string :external-format :utf8))
  45
  46 (eval-when (:compile-toplevel :load-toplevel :execute)
  47   (define-alien-type-translator void ()
  48     (parse-alien-type '(values) (sb-kernel:make-null-lexenv))))
  49 \f
  50
  51 (defun default-c-string-external-format ()
  52   (or *default-c-string-external-format*
  53       (setf *default-c-string-external-format*
  54             (sb-impl::default-external-format))))
  55
  56 (defun %naturalize-c-string (sap)
  57   (declare (type system-area-pointer sap))
  58   ;; It can be assumed that any modern implementation of strlen() reads 4, 8, 16,
  59   ;; or possibly even 32 bytes at a time when searching for the '\0' terminator.
  60   ;; As such, we expect it to be on average much faster than a loop over SAP-REF-8.
  61   ;; And much to my surprise, the foreign call overhead on x86-64 is so small that
  62   ;; there is not a minimum threshold length below which the foreign call costs too much.
  63   ;; With as few as 5 characters in the string, I saw 2x speedup.
  64   ;; Below that, it's about the same to do a foreign call versus staying in lisp.
  65   ;; The limiting case of a 0 length string would be faster without the foreign call,
  66   ;; but pre-checking would slow down every other case.
  67   (let* ((length (alien-funcall
  68                  (extern-alien "strlen" (function size-t system-area-pointer))
  69                  sap))
  70          (result (make-string length :element-type 'base-char)))
  71     ;; COPY-UB8 pins the lisp string, no need to do it here
  72     (sb-kernel:copy-ub8-from-system-area sap 0 result 0 length)
  73     result))