Function

Summary

Accesses a foreign array and can be compiled to efficient code.

Package

fli

Signature

foreign-typed-aref type array index => value

(setf foreign-typed-aref) value type array index => value

Arguments

type

A type specifier.

array

A foreign pointer.

index

A valid byte index for array .

Values

value

An element of array .

Description

The function foreign-typed-aref accesses a foreign array and is compiled to efficient code when compiled at safety 0. It corresponds to sys:typed-aref which accesses Lisp vectors.

type must evaluate to double-float , single-float , (unsigned-byte 32) , (signed-byte 32) , (unsigned-byte 16) , (signed-byte 16) , (unsigned-byte 8) or (signed-byte 8) .

array is a foreign pointer to an FLI array. Memory can be allocated with:

(fli:allocate-foreign-object 

 :type :double

 :nelems 

 (ceiling byte-size

          (fli:size-of :double)))

to get sufficient alignment for any call to foreign-typed-aref .

In the case the memory is allocated by the operating system the best approach is to reference it from Lisp by a pointer type, to avoid making a :c-array foreign type dynamically.

index is a byte index for array and should be (mod (* 2 1024 1024)) , but if it is declared to be of type fixnum then the compiler will optimize it slightly better. Some parts of the FLI (for example, allocate-foreign-object) assume fixnum sizes so it is best to use fixnums only.

Note: Efficient access to a Lisp vector object is also available. See sys:typed-aref in the LispWorks Reference Manual .

See also

foreign-aref