package ctypes
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doc/ctypes.stubs/Cstubs_structs/module-type-TYPE/index.html
Module type Cstubs_structs.TYPESource
include Ctypes_types.TYPE
Values representing C types
The type of values representing C types. There are two types associated with each typ value: the C type used to store and pass values, and the corresponding OCaml type. The type parameter indicates the OCaml type, so a value of type t typ is used to read and write OCaml values of type t. There are various uses of typ values, including
- constructing function types for binding native functions using
Foreign.foreign
- constructing pointers for reading and writing locations in C-managed storage using
ptr
The void type
Value representing the C void type. Void values appear in OCaml as the unit type, so using void in an argument or result type specification produces a function which accepts or returns unit.
Dereferencing a pointer to void is an error, as in C, and will raise IncompleteType.
Scalar types
The scalar types consist of the Arithmetic types and the Pointer types.
Arithmetic types
The arithmetic types consist of the signed and unsigned integer types (including character types) and the floating types. There are values representing both exact-width integer types (of 8, 16, 32 and 64 bits) and types whose size depend on the platform (signed and unsigned short, int, long, long long).
Signed integer types
Value representing the C type (signed) long.
Value representing the C type (signed) long long.
Value representing an integer type with the same storage requirements as an OCaml int.
Unsigned integer types
Value representing the C type unsigned char.
Value representing an 8-bit unsigned integer C type.
Value representing a 16-bit unsigned integer C type.
Value representing a 32-bit unsigned integer C type.
Value representing a 64-bit unsigned integer C type.
Value representing the C type size_t, an alias for one of the unsigned integer types. The actual size and alignment requirements for size_t vary between platforms.
Value representing the C type unsigned short.
Value representing the C type int.
Value representing the C type unsigned int.
Value representing the C type unsigned long.
Value representing the C type unsigned long long.
Floating types
Complex types
Value representing the C99 long-double-precision long double complex type.
Pointer types
C-compatible pointers
Construct a pointer type from an existing type (called the reference type).
Construct a pointer type from an existing type (called the reference type). This behaves like ptr, except that null pointers appear in OCaml as None.
A high-level representation of the string type.
On the C side this behaves like char *; on the OCaml side values read and written using string are simply native OCaml strings.
To avoid problems with the garbage collector, values passed using string are copied into immovable C-managed storage before being passed to C.
The string type representation is suitable for use in function argument types such as the following:
string @-> returning int
where the lifetime of the C-managed storage does not need to extend beyond the duration of the function call. However, it is not suitable for use in struct or union fields
field s "x" string
because it does not provide a way to manage the lifetime of the C-managed storage.
A high-level representation of the string type. This behaves like string, except that null pointers appear in OCaml as None.
OCaml pointers
Value representing the directly mapped storage of an OCaml string.
Value representing the directly mapped storage of an OCaml byte array.
Array types
C array types
Construct a sized array type from a length and an existing type (called the element type).
Bigarray types
val bigarray :
< element : 'a
; layout : Bigarray_compat.c_layout
; ba_repr : 'b
; dims : 'dims
; bigarray : 'bigarray
; carray : _ >
Ctypes_static.bigarray_class ->
'dims ->
('a, 'b) Bigarray_compat.kind ->
'bigarray typConstruct a sized C-layout bigarray type representation from a bigarray class, the dimensions, and the Bigarray_compat.kind.
val fortran_bigarray :
< element : 'a
; layout : Bigarray_compat.fortran_layout
; ba_repr : 'b
; dims : 'dims
; bigarray : 'bigarray
; carray : _ >
Ctypes_static.bigarray_class ->
'dims ->
('a, 'b) Bigarray_compat.kind ->
'bigarray typConstruct a sized Fortran-layout bigarray type representation from a bigarray class, the dimensions, and the Bigarray_compat.kind.
typ_of_bigarray_kind k is the type corresponding to the Bigarray kind k.
Struct and union types
Construct a new structure type. The type value returned is incomplete and can be updated using field until it is passed to seal, at which point the set of fields is fixed.
The type ('_s structure typ) of the expression returned by the call structure tag includes a weak type variable, which can be explicitly instantiated to ensure that the OCaml values representing different C structure types have incompatible types. Typical usage is as follows:
type tagname
let tagname : tagname structure typ = structure "tagname"
val field :
't typ ->
string ->
'a typ ->
('a, ('s, [< `Struct | `Union ]) Ctypes_static.structured as 't) fieldfield ty label ty' adds a field of type ty' with label label to the structure or union type ty and returns a field value that can be used to read and write the field in structure or union instances (e.g. using getf and setf).
Attempting to add a field to a union type that has been sealed with seal is an error, and will raise ModifyingSealedType.
seal t completes the struct or union type t so that no further fields can be added. Struct and union types must be sealed before they can be used in a way that involves their size or alignment; see the documentation for IncompleteType for further details.
View types
val view :
?format_typ:((Format.formatter -> unit) -> Format.formatter -> unit) ->
?format:(Format.formatter -> 'b -> unit) ->
read:('a -> 'b) ->
write:('b -> 'a) ->
'a typ ->
'b typview ~read:r ~write:w t creates a C type representation t' which behaves like t except that values read using t' are subsequently transformed using the function r and values written using t' are first transformed using the function w.
For example, given suitable definitions of string_of_char_ptr and char_ptr_of_string, the type representation
view ~read:string_of_char_ptr ~write:char_ptr_of_string (ptr char)
can be used to pass OCaml strings directly to and from bound C functions, or to read and write string members in structs and arrays. (In fact, the string type representation is defined in exactly this way.)
The optional argument format_typ is used by the Ctypes.format_typ and string_of_typ functions to print the type at the top level and elsewhere. If format_typ is not supplied the printer for t is used instead.
The optional argument format is used by the Ctypes.format and string_of functions to print the values. If format_val is not supplied the printer for t is used instead.
typedef t name creates a C type representation t' which is equivalent to t except its name is printed as name.
This is useful when generating C stubs involving "anonymous" types, for example: typedef struct { int f } typedef_name;
Abstract types
Create an abstract type specification from the size and alignment requirements for the type.
Injection of concrete types
lift_typ t turns a concrete type representation into an abstract type representation.
For example, retrieving struct layout from C involves working with an abstract representation of types which do not support operations such as sizeof. The lift_typ function makes it possible to use concrete type representations wherever such abstract type representations are needed.
Function types
Abstract interface to C function type descriptions
The type of values representing C function types. A value of type t fn can be used to bind to C functions and to describe type of OCaml functions passed to C.
Construct a function type from a type and an existing function type. This corresponds to prepending a parameter to a C function parameter list. For example,
int @-> ptr void @-> returning float
describes a function type that accepts two arguments -- an integer and a pointer to void -- and returns a float.
Function pointer types
The type of values representing C function pointer types.
Construct a function pointer type from an existing function type (called the reference type).