125 lines
4.1 KiB
Racket
125 lines
4.1 KiB
Racket
#lang scribble/doc
|
|
@(require "utils.rkt")
|
|
|
|
@title{Miscellaneous Support}
|
|
|
|
|
|
@defproc[(regexp-replaces [objname (or/c string? bytes? symbol?)]
|
|
[substs (listof (list regexp? string?))])
|
|
string?]{
|
|
|
|
A function that is convenient for many interfaces where the foreign
|
|
library has some naming convention that you want to use in your
|
|
interface as well. The @racket[objname] argument can be any value
|
|
that will be used to name the foreign object; it is first converted
|
|
into a string, and then modified according to the given
|
|
@racket[substs] list in sequence, where each element in this list is a
|
|
list of a regular expression and a substitution string. Usually,
|
|
@racket[regexp-replace*] is used to perform the substitution, except
|
|
for cases where the regular expression begins with a @litchar{^} or
|
|
ends with a @litchar{$}, in which case @racket[regexp-replace] is
|
|
used.
|
|
|
|
For example, the following makes it convenient to define Racket
|
|
bindings such as @racket[foo-bar] for foreign names like
|
|
@racket[MyLib_foo_bar]:
|
|
|
|
@racketblock[
|
|
(define mylib (ffi-lib "mylib"))
|
|
(define-syntax defmyobj
|
|
(syntax-rules (:)
|
|
[(_ name : type ...)
|
|
(define name
|
|
(get-ffi-obj
|
|
(regexp-replaces 'name '((#rx"-" "_")
|
|
(#rx"^" "MyLib_")))
|
|
mylib (_fun type ...)))]))
|
|
(defmyobj foo-bar : _int -> _int)
|
|
]}
|
|
|
|
|
|
@defproc[(list->cblock [lst list?] [type ctype?]) any]{
|
|
|
|
Allocates a memory block of an appropriate size, and initializes it
|
|
using values from @racket[lst] and the given @racket[type]. The
|
|
@racket[lst] must hold values that can all be converted to C values
|
|
according to the given @racket[type].}
|
|
|
|
|
|
@defproc[(vector->cblock [vec vector?] [type type?]) any]{
|
|
|
|
Like @racket[list->cblock], but for Racket vectors.}
|
|
|
|
|
|
@defproc[(vector->cpointer [vec vector?]) cpointer?]{
|
|
|
|
Returns a pointer to an array of @racket[_scheme] values, which is the
|
|
internal representation of @racket[vec].}
|
|
|
|
@defproc[(flvector->cpointer [flvec flvector?]) cpointer?]{
|
|
|
|
Returns a pointer to an array of @racket[_double] values, which is the
|
|
internal representation of @racket[flvec].}
|
|
|
|
@defproc[(saved-errno) exact-integer?]{
|
|
|
|
Returns the value most recently saved (in the current thread) after a
|
|
foreign call with a non-@racket[#f] @racket[#:save-errno] option (see
|
|
@racket[_fun] and @racket[_cprocedure]).}
|
|
|
|
@defproc[(lookup-errno [sym (or/c 'EINTR 'EEXIST 'EAGAIN)])
|
|
exact-integer?]{
|
|
|
|
Returns a platform-specific value corresponding to a Posix @tt{errno}
|
|
symbol. The set of supported symbols is likely to expand in the
|
|
future.}
|
|
|
|
|
|
@defproc[(cast [v any/c] [from-type ctype?] [to-type ctype?]) any/c]{
|
|
|
|
Converts @racket[v] from a value matching @racket[from-type] to a
|
|
value matching @racket[to-type], where @racket[(ctype-sizeof from-type)]
|
|
matches @racket[(ctype-sizeof to-type)].
|
|
|
|
The conversion is equivalent to
|
|
|
|
@racketblock[
|
|
(let ([p (malloc from-type)])
|
|
(ptr-set! p from-type v)
|
|
(ptr-ref p to-type))
|
|
]
|
|
|
|
Beware of potential pitfalls with @racket[cast]:
|
|
|
|
@itemlist[
|
|
|
|
@item{If @racket[v] is a pointer that refers to memory that is
|
|
managed by the garbage collector, @racket[from-type] and
|
|
@racket[to-type] normally should be based on
|
|
@racket[_gcpointer], not @racket[_pointer]; see also
|
|
@racket[_gcable].}
|
|
|
|
@item{If @racket[v] is a pointer with an offset component (e.g., from
|
|
@racket[ptr-add]), the offset is folded into the pointer base
|
|
for the result. Consequently, @racket[cast] generally should
|
|
not be used on a source pointer that refers to memory that is
|
|
managed by the garbage collector and that has an offset, unless
|
|
the memory is specially allocated to allow interior pointers.}
|
|
|
|
]}
|
|
|
|
|
|
@defproc[(cblock->list [cblock any/c] [type ctype?] [length exact-nonnegative-integer?])
|
|
list?]{
|
|
|
|
Converts C @racket[cblock], which is a vector of @racket[type]s, to a
|
|
Racket list. The arguments are the same as in the
|
|
@racket[list->cblock]. The @racket[length] must be specified because
|
|
there is no way to know where the block ends.}
|
|
|
|
|
|
@defproc[(cblock->vector [cblock any/c] [type ctype?] [length exact-nonnegative-integer?])
|
|
vector?]{
|
|
|
|
Like @racket[cblock->vector], but for Racket vectors.}
|