fe04097 Nov 4, 2012
@luismbo @orivej @jhoehle
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\input texinfo @c -*-texinfo-*-
@c %**start of header
@settitle CFFI-SYS Interface Specification
@c Show types in the same index as the functions.
@synindex tp fn
Copyright @copyright{} 2005-2006, James Bielman <jamesjb at>
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the ``Software''), to deal in the Software without
restriction, including without limitation the rights to use, copy,
modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
@sc{The software is provided ``as is'', without warranty of any kind,
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whether in an action of contract, tort or otherwise, arising from,
out of or in connection with the software or the use or other
dealings in the software.}
@end quotation
@end copying
@macro impnote {text}
@emph{Implementor's note: \text\}
@end macro
@c %**end of header
@dircategory Software development
* CFFI Sys spec: (cffi-sys-spec). CFFI Sys spec.
@end direntry
@title CFFI-SYS Interface Specification
@c @subtitle Version X.X
@c @author James Bielman
@vskip 0pt plus 1filll
@end titlepage
@node Top
@top cffi-sys
@end ifnottex
* Introduction::
* Built-In Foreign Types::
* Operations on Foreign Types::
* Basic Pointer Operations::
* Foreign Memory Allocation::
* Memory Access::
* Foreign Function Calling::
* Loading Foreign Libraries::
* Foreign Globals::
* Symbol Index::
@end menu
@node Introduction
@chapter Introduction
@acronym{CFFI}, the Common Foreign Function Interface, purports to be
a portable foreign function interface for Common Lisp.
This specification defines a set of low-level primitives that must be
defined for each Lisp implementation supported by @acronym{CFFI}.
These operators are defined in the @code{CFFI-SYS} package.
The @code{CFFI} package uses the @code{CFFI-SYS} interface
to implement an extensible foreign type system with support for
typedefs, structures, and unions, a declarative interface for
defining foreign function calls, and automatic conversion of
foreign function arguments to/from Lisp types.
Please note the following conventions that apply to everything in
@itemize @bullet
Functions in @code{CFFI-SYS} that are low-level versions of functions
exported from the @code{CFFI} package begin with a leading
percent-sign (eg. @code{%mem-ref}).
Where ``foreign type'' is mentioned as the kind of an argument, the
meaning is restricted to that subset of all foreign types defined in
@ref{Built-In Foreign Types}. Support for higher-level types is
always defined in terms of those lower-level types in @code{CFFI}
@end itemize
@node Built-In Foreign Types
@chapter Built-In Foreign Types
@deftp {Foreign Type} :char
@deftpx {Foreign Type} :unsigned-char
@deftpx {Foreign Type} :short
@deftpx {Foreign Type} :unsigned-short
@deftpx {Foreign Type} :int
@deftpx {Foreign Type} :unsigned-int
@deftpx {Foreign Type} :long
@deftpx {Foreign Type} :unsigned-long
@deftpx {Foreign Type} :long-long
@deftpx {Foreign Type} :unsigned-long-long
These types correspond to the native C integer types according to the
ABI of the system the Lisp implementation is compiled against.
@end deftp
@deftp {Foreign Type} :int8
@deftpx {Foreign Type} :uint8
@deftpx {Foreign Type} :int16
@deftpx {Foreign Type} :uint16
@deftpx {Foreign Type} :int32
@deftpx {Foreign Type} :uint32
@deftpx {Foreign Type} :int64
@deftpx {Foreign Type} :uint64
Foreign integer types of specific sizes, corresponding to the C types
defined in @code{stdint.h}.
@end deftp
@deftp {Foreign Type} :size
@deftpx {Foreign Type} :ssize
@deftpx {Foreign Type} :ptrdiff
@deftpx {Foreign Type} :time
Foreign integer types corresponding to the standard C types (without
the @code{_t} suffix).
@end deftp
@impnote{I'm sure there are more of these that could be useful, let's
add any types that can't be defined portably to this list as
@deftp {Foreign Type} :float
@deftpx {Foreign Type} :double
The @code{:float} type represents a C @code{float} and a Lisp
@code{single-float}. @code{:double} represents a C @code{double} and a
Lisp @code{double-float}.
@end deftp
@deftp {Foreign Type} :pointer
A foreign pointer to an object of any type, corresponding to
@code{void *}.
@end deftp
@deftp {Foreign Type} :void
No type at all. Only valid as the return type of a function.
@end deftp
@node Operations on Foreign Types
@chapter Operations on Built-in Foreign Types
@defun %foreign-type-size type @result{} size
Return the @var{size}, in bytes, of objects having foreign type
@var{type}. An error is signalled if @var{type} is not a known
built-in foreign type.
@end defun
@defun %foreign-type-alignment type @result{} alignment
Return the default alignment in bytes for structure members of foreign
type @var{type}. An error is signalled if @var{type} is not a known
built-in foreign type.
@impnote{Maybe this should take an optional keyword argument specifying an
alternate alignment system, eg. :mac68k for 68000-compatible alignment
on Darwin.}
@end defun
@node Basic Pointer Operations
@chapter Basic Pointer Operations
@defun pointerp ptr @result{} boolean
Return true if @var{ptr} is a foreign pointer.
@end defun
@defun null-pointer @result{} pointer
Return a null foreign pointer.
@end defun
@defun null-pointer-p ptr @result{} boolean
Return true if @var{ptr} is a null foreign pointer.
@end defun
@defun make-pointer address @result{} pointer
Return a pointer corresponding to the numeric integer @var{address}.
@end defun
@defun inc-pointer ptr offset @result{} pointer
Return the result of numerically incrementing @var{ptr} by @var{offset}.
@end defun
@node Foreign Memory Allocation
@chapter Foreign Memory Allocation
@defun foreign-alloc size @result{} pointer
Allocate @var{size} bytes of foreign-addressable memory and return
a @var{pointer} to the allocated block. An implementation-specific
error is signalled if the memory cannot be allocated.
@end defun
@defun foreign-free ptr @result{} unspecified
Free a pointer @var{ptr} allocated by @code{foreign-alloc}. The
results are undefined if @var{ptr} is used after being freed.
@end defun
@defmac with-foreign-pointer (var size &optional size-var) &body body
Bind @var{var} to a pointer to @var{size} bytes of
foreign-accessible memory during @var{body}. Both @var{ptr} and the
memory block it points to have dynamic extent and may be stack
allocated if supported by the implementation. If @var{size-var} is
supplied, it will be bound to @var{size} during @var{body}.
@end defmac
@node Memory Access
@chapter Memory Access
@deffn {Accessor} %mem-ref ptr type &optional offset
Dereference a pointer @var{offset} bytes from @var{ptr} to an object
for reading (or writing when used with @code{setf}) of built-in type
@end deffn
@heading Example
;; An impractical example, since time returns the time as well,
;; but it demonstrates %MEM-REF. Better (simple) examples wanted!
(with-foreign-pointer (p (foreign-type-size :time))
(foreign-funcall "time" :pointer p :time)
(%mem-ref p :time))
@end lisp
@node Foreign Function Calling
@chapter Foreign Function Calling
@defmac %foreign-funcall name @{arg-type arg@}* &optional result-type @result{} object
@defmacx %foreign-funcall-pointer ptr @{arg-type arg@}* &optional result-type @result{} object
Invoke a foreign function called @var{name} in the foreign source code.
Each @var{arg-type} is a foreign type specifier, followed by
@var{arg}, Lisp data to be converted to foreign data of type
@var{arg-type}. @var{result-type} is the foreign type of the
function's return value, and is assumed to be @code{:void} if not
@code{%foreign-funcall-pointer} takes a pointer @var{ptr} to the
function, as returned by @code{foreign-symbol-pointer}, rather than a
string @var{name}.
@end defmac
@heading Examples
;; Calling a standard C library function:
(%foreign-funcall "sqrtf" :float 16.0 :float) @result{} 4.0
@end lisp
;; Dynamic allocation of a buffer and passing to a function:
(with-foreign-ptr (buf 255 buf-size)
(%foreign-funcall "gethostname" :pointer buf :size buf-size :int)
;; Convert buf to a Lisp string using MAKE-STRING and %MEM-REF or
;; a portable CFFI function such as CFFI:FOREIGN-STRING-TO-LISP.
@end lisp
@node Loading Foreign Libraries
@chapter Loading Foreign Libraries
@defun %load-foreign-library name @result{} unspecified
Load the foreign shared library @var{name}.
@impnote{There is a lot of behavior to decide here. Currently I lean
toward not requiring NAME to be a full path to the library so
we can search the system library directories (maybe even get
LD_LIBRARY_PATH from the environment) as necessary.}
@end defun
@node Foreign Globals
@chapter Foreign Globals
@defun foreign-symbol-pointer name @result{} pointer
Return a pointer to a foreign symbol @var{name}.
@end defun
@node Symbol Index
@unnumbered Symbol Index
@printindex fn