5.5 Defining Bindings
| (require ffi/unsafe/define) | package: base |
syntax
(define-ffi-definer define-id ffi-lib-expr option ...)
option = #:provide provide-id | #:define core-define-id | #:default-make-fail default-make-fail-expr | #:make-c-id make-c-id
(define-id id type-expr bind-option ...)
bind-option = #:c-id c-id | #:wrap wrap-expr | #:make-fail make-fail-expr | #:fail fail-expr
A define-id form binds id by extracting a binding with the name c-id from the library produced by ffi-lib-expr, where c-id defaults to id. The other options support further wrapping and configuration:
Before the extracted result is bound as id, it is passed to the result of wrap-expr, which defaults to values. Expressions such as (allocator delete) or (deallocator) are useful as wrap-exprs.
The #:make-fail and #:fail options are mutually exclusive; if make-fail-expr is provided, it is applied to 'id to obtain the last argument to get-ffi-obj; if fail-expr is provided, it is supplied directly as the last argument to get-ffi-obj. The make-not-available function is useful as make-fail-expr to cause a use of id to report an error when it is applied if c-id was not found in the foreign library.
If provided, the #:make-c-id option changes the default behavior of c-id using an ffi identifier convention, such as converting hyphens to underscores or camel case. Several conventions are provided by ffi/unsafe/define/conventions.
If provide-id is provided to define-ffi-definer, then define-id also provides its binding using provide-id. The provide-protected form is usually a good choice for provide-id.
If core-define-id is provided to define-ffi-definer, then core-define-id is used in place of define in the expansion of define-id for each binding.
If default-make-fail-expr is provided to define-ffi-definer, it serves as the default #:make-fail value for define-id.
For example,
(define-ffi-definer define-gtk gtk-lib)
binds define-gtk to extract FFI bindings from gtk-lib, so that gtk_rc_parse could be bound as
If gtk_rc_parse is not found, then define-gtk reports an error immediately. If define-gtk is instead defined with
(define-ffi-definer define-gtk gtk-lib #:default-make-fail make-not-available)
then if gtk_rc_parse is not found in gtk-lib, an error is reported only when gtk_rc_parse is called.
Changed in version 6.9.0.5 of package base: Added #:make-c-id parameter.
procedure
(make-not-available name) → (#:rest list? -> any/c)
name : symbol?
syntax
(provide-protected provide-spec ...)
5.5.1 FFI Identifier Conventions
| (require ffi/unsafe/define/conventions) | package: base |
This module provides several FFI identifier conventions for use with #:make-c-id in define-ffi-definer. A FFI identifier convention is any syntax transformer that converts one identifier to another.
Added in version 6.9.0.5 of package base.
(define-ffi-definer define-gtk gtk-lib #:make-c-id convention:hyphen->underscore) (define-gtk gtk-rc-parse (_fun _path -> _void))
(define-ffi-definer define-calib camel-lib #:make-c-id conventon:hyphen->camelcase) (define-calib camel-case-variable (_fun -> _void))