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-SYS package.
The CFFI package uses the 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
CFFI-SYS:
CFFI-SYS that are low-level versions of functions
exported from the CFFI package begin with a leading
percent-sign (eg. %mem-ref).
CFFI
proper.
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
stdint.h.
Foreign integer types corresponding to the standard C types (without the
_tsuffix).
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.
The
:floattype represents a Cfloatand a Lispsingle-float.:doublerepresents a Cdoubleand a Lispdouble-float.
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 byforeign-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 Typesforeign-alloc: Foreign Memory Allocationforeign-free: Foreign Memory Allocationforeign-symbol-pointer: Foreign Globalsinc-pointer: Basic Pointer Operationsmake-pointer: Basic Pointer Operationsnull-pointer: Basic Pointer Operationsnull-pointer-p: Basic Pointer Operationspointerp: Basic Pointer Operationswith-foreign-pointer: Foreign Memory Allocation