Pointers and extern

Pointers are the primary way Rux exchanges memory with C and other native libraries. Typed pointers, *const for read-only buffers, and *opaque for handles all map directly onto C pointer types.

extern func memcpy(dst: *opaque, src: *const opaque, n: uint) -> *opaque;

let src = [1, 2, 3, 4];
var dst: int32[4];
memcpy(dst.data, src.data, sizeof(int32) * src.length);

Pass a buffer by handing the callee its data pointer and length; the address identifies the first byte and the length bounds the access. Because C strings are null-terminated and Rux slices are not, account for the terminator explicitly when crossing the boundary.

See the Foreign Function Interface chapter for more on calling native code.

See Also

• Pointers — addresses and how a pointer is stored
• Pointer Types — *const and *opaque, which map onto C pointer types
• Foreign Function Interface — declaring and calling native functions