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The Library
object represents a native library loaded by the ctypes open()
method. Its methods let you declare symbols exported by the library, and to manage the library.
Method overview
close(); |
; |
Methods
close()
Closes the library. You need to call this once you're done using the library.
close();
Parameters
None.
declare()
Declares an API from the native library, allowing it to be used from JavaScript. This can be used both for exported data symbols and for functions.
CData declare( name[, abi, returnType argType1, ...] );
Parameters
name
- The name of the symbol exported by the native library that is to be declared as usable from JavaScript
abi
- The
ABI
used by the exported function; this will bectypes.default_abi
for most libraries, except for Windows libraries, which will bectypes.winapi_abi
orctypes.stdcall_abi
. See ABI constants. You don't need to provide this for exported data; it's only needed for function declarations. returnType
- The
CType
type returned by the defined API, if it's a function. This parameter should not be provided if the API is an exported data symbol. argType1...argTypeN
- Zero or more parameter
CType
may be specified for the parameters of the function being declared. These should not be provided if the API is an exported data symbol rather than a function.
Return value
A FunctionType
CData
object representing the declared API.
Exceptions thrown
TypeError
- The return type was specified as an array.
Alternative Syntax
Another use for ctypes.declare is to get non-function/non-methods from libraries. The syntax for this is seen in Firefox codebase here:
https://dxr.mozilla.org/mozilla-central/source/js/src/ctypes/Library.cpp?offset=0#271
This shows that we can also supply only two arguments to the declare function. The first being the same as in the above example, name, which is the name of the symbol to export. And in place of the abi argument, we will pass in the type of this export. For example, from the Objective-C library we can export the symbol which holds the address to an external block. This would be done like this:
var objc = ctypes.open(ctypes.libraryName('objc')); objc.declare('_NSConcreteGlobalBlock', ctypes.voidptr_t);
-
See Also