chickadee » foreign » access » define-foreign-type

Defines an alias for TYPE with the name NAME (a symbol). TYPE may be a type-specifier or a string naming a C type. The namespace of foreign type specifiers is separate from the normal Scheme namespace. The optional arguments ARGCONVERT and RETCONVERT should evaluate to procedures that map argument- and result-values to a value that can be transformed to TYPE:

(define-foreign-type char-vector 
  nonnull-c-string
  (compose list->string vector->list)
  (compose list->vector string->list) )

(define strlen
  (foreign-lambda int "strlen" char-vector) )

(strlen '#(#\a #\b #\c))                      ==> 3

(define memset
  (foreign-lambda char-vector "memset" char-vector char int) )

(memset '#(#_ #_ #_) #\X 3)                ==> #(#\X #\X #\X)

Foreign type-definitions are only visible in the compilation-unit in which they are defined, so use include to use the same definitions in multiple files.