► |  | The 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
| Bibliography
| Index

▼ | 3 | C Types

3.1 | Type Constructors
3.2 | Numeric Types
3.3 | Other Atomic Types
3.4 | String Types
3.5 | Pointer Types
3.6 | Function Types
3.7 | C Struct Types
3.8 | C Array Types
3.9 | C Union Types
3.10 | Enumerations and Masks

On this page:

make-ctype
ctype?
ctype-sizeof
ctype-alignof
ctype->layout
compiler-sizeof

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#### 3.1`` Type Constructors

> procedure (make-ctype type scheme-to-c c-to-scheme) → ctype?
> type : ctype?
> scheme-to-c : (or/c #f (any/c . -> . any))
> c-to-scheme : (or/c #f (any/c . -> . any))

Creates a new C type value whose representation for foreign code is the same as type’s. The given conversions functions convert to and from the Racket representation of type. Either conversion function can be #f, meaning that the conversion for the corresponding direction is the identity function. If both functions are #f, type is returned.

> procedure (ctype? v) → boolean?
> v : any/c

Returns #t if v is a C type, #f otherwise.

Examples:
> > (ctype? _int)
> #t
> > (ctype? (_fun _int -> _int))
> #t
> > (ctype? #f)
> #f
> > (ctype? "foo")
> #f

> procedure (ctype-sizeof type) → exact-nonnegative-integer?
> type : ctype?
> (ctype-alignof type) → exact-nonnegative-integer?
> type : ctype?

Returns the size or alignment of a given type for the current platform.

Examples:
> > (ctype-sizeof _int)
> 4
> > (ctype-sizeof (_fun _int -> _int))
> 8
> > (ctype-alignof _int)
> 4
> > (ctype-alignof (_fun _int -> _int))
> 8

> procedure (ctype->layout type)
> → (flat-rec-contract rep symbol? (listof rep))
> type : ctype?

Returns a value to describe the eventual C representation of the type. It can be any of the following symbols:

> 'int8 'uint8 'int16 'uint16 'int32 'uint32 'int64 'uint64
> 'float 'double 'bool 'void 'pointer 'fpointer
> 'bytes 'string/ucs-4 'string/utf-16

The result can also be a list, which describes a C struct whose element representations are provided in order within the list. Finally, the result can be a vector of size 2 containing an element representation followed by an exact-integer count.

Examples:
> > (ctype->layout _int)
> 'int32
> > (ctype->layout _void)
> 'void
> > (ctype->layout (_fun _int -> _int))
> 'fpointer

> procedure (compiler-sizeof sym) → exact-nonnegative-integer?
> sym : (or/c symbol? (listof symbol?))

Possible values for sym are 'int, 'char, 'short, 'long, '*, 'void, 'float, 'double, or lists of symbols, such as '(long long). The result is the size of the corresponding type according to the C sizeof operator for the current platform. The compiler-sizeof operation should be used to gather information about the current platform, such as defining alias type like _int to a known type like _int32.

Examples:
> > (compiler-sizeof 'int)
> 4
> > (compiler-sizeof '(long long))
> 8

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