Copyright © 2005-2006, James Bielman <jamesjb at jamesjb.com>
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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 CFFI.
These operators are defined in the
CFFI package uses the
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
CFFI-SYSthat are low-level versions of functions exported from the
CFFIpackage begin with a leading percent-sign (eg.
These types correspond to the native C integer types according to the ABI of the system the Lisp implementation is compiled against.
Foreign integer types of specific sizes, corresponding to the C types defined in
Foreign integer types corresponding to the standard C types (without the
Implementor's note: 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 necessary.
:floattype represents a C
floatand a Lisp
:doublerepresents a C
doubleand a Lisp
Return the size, in bytes, of objects having foreign type type. An error is signalled if type is not a known built-in foreign type.
Return the default alignment in bytes for structure members of foreign type type. An error is signalled if type is not a known built-in foreign type.
Implementor's note: Maybe this should take an optional keyword argument specifying an alternate alignment system, eg. :mac68k for 68000-compatible alignment on Darwin.
Return a pointer corresponding to the numeric integer address.
Return the result of numerically incrementing ptr by offset.
Allocate size bytes of foreign-addressable memory and return a pointer to the allocated block. An implementation-specific error is signalled if the memory cannot be allocated.
Free a pointer ptr allocated by
foreign-alloc. The results are undefined if ptr is used after being freed.
Bind var to a pointer to size bytes of foreign-accessible memory during body. Both ptr and the memory block it points to have dynamic extent and may be stack allocated if supported by the implementation. If size-var is supplied, it will be bound to size during body.
Dereference a pointer offset bytes from ptr to an object for reading (or writing when used with
setf) of built-in type type.
;; 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))
Invoke a foreign function called name in the foreign source code.
Each arg-type is a foreign type specifier, followed by arg, Lisp data to be converted to foreign data of type arg-type. result-type is the foreign type of the function's return value, and is assumed to be
:voidif not supplied.
%foreign-funcall-pointertakes a pointer ptr to the function, as returned by
foreign-symbol-pointer, rather than a string name.
;; Calling a standard C library function: (%foreign-funcall "sqrtf" :float 16.0 :float) => 4.0
;; 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. )
Load the foreign shared library name.
Implementor's note: 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.
%foreign-funcall: Foreign Function Calling
%foreign-funcall-pointer: Foreign Function Calling
%foreign-type-alignment: Operations on Foreign Types
%foreign-type-size: Operations on Foreign Types
%load-foreign-library: Loading Foreign Libraries
%mem-ref: Memory Access
:char: Built-In Foreign Types
:double: Built-In Foreign Types
:float: Built-In Foreign Types
:int: Built-In Foreign Types
:int16: Built-In Foreign Types
:int32: Built-In Foreign Types
:int64: Built-In Foreign Types
:int8: Built-In Foreign Types
:long: Built-In Foreign Types
:long-long: Built-In Foreign Types
:pointer: Built-In Foreign Types
:ptrdiff: Built-In Foreign Types
:short: Built-In Foreign Types
:size: Built-In Foreign Types
:ssize: Built-In Foreign Types
:time: Built-In Foreign Types
:uint16: Built-In Foreign Types
:uint32: Built-In Foreign Types
:uint64: Built-In Foreign Types
:uint8: Built-In Foreign Types
:unsigned-char: Built-In Foreign Types
:unsigned-int: Built-In Foreign Types
:unsigned-long: Built-In Foreign Types
:unsigned-long-long: Built-In Foreign Types
:unsigned-short: Built-In Foreign Types
:void: Built-In Foreign Types
foreign-alloc: Foreign Memory Allocation
foreign-free: Foreign Memory Allocation
foreign-symbol-pointer: Foreign Globals
inc-pointer: Basic Pointer Operations
make-pointer: Basic Pointer Operations
null-pointer: Basic Pointer Operations
null-pointer-p: Basic Pointer Operations
pointerp: Basic Pointer Operations
with-foreign-pointer: Foreign Memory Allocation