7 Unexported Primitive Functions

▼ |  | FFI: Racket Foreign Interface

1 | Overview
2 | Loading Foreign Libraries
3 | C Types
4 | Pointer Functions
5 | Derived Utilities
6 | Miscellaneous Support
7 | Unexported Primitive Functions
| Index

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ffi-obj
ffi-obj?
ffi-obj-lib
ffi-obj-name
ctype-basetype
ctype-scheme->c
ctype-c->scheme
ffi-call
ffi-callback
ffi-callback?

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### 7`` Unexported Primitive Functions

Parts of the ffi/unsafe library are implemented by the Racket built-in '#%foreign module. The '#%foreign module is not intended for direct use, but it exports the following procedures. If you find any of these useful, please let us know.

( ffi-obj objname lib) → any
objname : ( or/c string? bytes? symbol?)
lib : ( or/c ffi-lib? path-string? #f)

Pulls out a foreign object from a library, returning a Racket value that can be used as a pointer. If a name is provided instead of a foreign-library value, ffi-lib is used to create a library object.

( ffi-obj? x) → boolean?
x : any/c
( ffi-obj-lib obj) → ffi-lib?
obj : ffi-obj?
( ffi-obj-name obj) → string?
obj : ffi-obj?

A predicate for objects returned by ffi-obj, and accessor functions that return its corresponding library object and name. These values can also be used as C pointer objects.

( ctype-basetype type) → ( or/c ctype? #f)
type : ctype?
( ctype-scheme->c type) → procedure?
type : ctype?
( ctype-c->scheme type) → procedure?
type : ctype?

Accessors for the components of a C type object, made by make-ctype. The ctype-basetype selector returns a symbol for primitive types that names the type, a list of ctypes for cstructs, and another ctype for user-defined ctypes.

( ffi-call ptr in-types out-type [abi]) → any
ptr : any/c
in-types : ( listof ctype?)
out-type : ctype?
abi : ( or/c symbol/c #f) = #f

The primitive mechanism that creates Racket “callout” values. The given ptr (any pointer value, including ffi-obj values) is wrapped in a Racket-callable primitive function that uses the types to specify how values are marshaled.

The optional abi argument determines the foreign ABI that is used. #f or 'default will use a platform-dependent default; other possible values are 'stdcall and 'sysv (the latter corresponds to “cdecl”). This is especially important on Windows, where most system functions are 'stdcall, which is not the default.

( ffi-callback |  | proc |  |  |  |
|  | in-types |  |  |  |
|  | out-type |  |  |  |
| [ | abi |  |  |  |
|  | atomic?]) |  | → |  | ffi-callback?

proc : any/c
in-types : any/c
out-type : any/c
abi : ( or/c symbol/c #f) = #f
atomic? : any/c = #f

The symmetric counterpart of ffi-call. It receives a Racket procedure and creates a callback object, which can also be used as a pointer. This object can be used as a C-callable function, which invokes proc using the types to specify how values are marshaled.

( ffi-callback? x) → boolean?
x : any/c

A predicate for callback values that are created by ffi-callback.
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