1 .. highlightlang:: c 2 3 .. _capsules: 4 5 Capsules 6 -------- 7 8 .. index:: object: Capsule 9 10 Refer to :ref:`using-capsules` for more information on using these objects. 11 12 13 .. c:type:: PyCapsule 14 15 This subtype of :c:type:`PyObject` represents an opaque value, useful for C 16 extension modules who need to pass an opaque value (as a :c:type:`void\*` 17 pointer) through Python code to other C code. It is often used to make a C 18 function pointer defined in one module available to other modules, so the 19 regular import mechanism can be used to access C APIs defined in dynamically 20 loaded modules. 21 22 .. c:type:: PyCapsule_Destructor 23 24 The type of a destructor callback for a capsule. Defined as:: 25 26 typedef void (*PyCapsule_Destructor)(PyObject *); 27 28 See :c:func:`PyCapsule_New` for the semantics of PyCapsule_Destructor 29 callbacks. 30 31 32 .. c:function:: int PyCapsule_CheckExact(PyObject *p) 33 34 Return true if its argument is a :c:type:`PyCapsule`. 35 36 37 .. c:function:: PyObject* PyCapsule_New(void *pointer, const char *name, PyCapsule_Destructor destructor) 38 39 Create a :c:type:`PyCapsule` encapsulating the *pointer*. The *pointer* 40 argument may not be *NULL*. 41 42 On failure, set an exception and return *NULL*. 43 44 The *name* string may either be *NULL* or a pointer to a valid C string. If 45 non-*NULL*, this string must outlive the capsule. (Though it is permitted to 46 free it inside the *destructor*.) 47 48 If the *destructor* argument is not *NULL*, it will be called with the 49 capsule as its argument when it is destroyed. 50 51 If this capsule will be stored as an attribute of a module, the *name* should 52 be specified as ``modulename.attributename``. This will enable other modules 53 to import the capsule using :c:func:`PyCapsule_Import`. 54 55 56 .. c:function:: void* PyCapsule_GetPointer(PyObject *capsule, const char *name) 57 58 Retrieve the *pointer* stored in the capsule. On failure, set an exception 59 and return *NULL*. 60 61 The *name* parameter must compare exactly to the name stored in the capsule. 62 If the name stored in the capsule is *NULL*, the *name* passed in must also 63 be *NULL*. Python uses the C function :c:func:`strcmp` to compare capsule 64 names. 65 66 67 .. c:function:: PyCapsule_Destructor PyCapsule_GetDestructor(PyObject *capsule) 68 69 Return the current destructor stored in the capsule. On failure, set an 70 exception and return *NULL*. 71 72 It is legal for a capsule to have a *NULL* destructor. This makes a *NULL* 73 return code somewhat ambiguous; use :c:func:`PyCapsule_IsValid` or 74 :c:func:`PyErr_Occurred` to disambiguate. 75 76 77 .. c:function:: void* PyCapsule_GetContext(PyObject *capsule) 78 79 Return the current context stored in the capsule. On failure, set an 80 exception and return *NULL*. 81 82 It is legal for a capsule to have a *NULL* context. This makes a *NULL* 83 return code somewhat ambiguous; use :c:func:`PyCapsule_IsValid` or 84 :c:func:`PyErr_Occurred` to disambiguate. 85 86 87 .. c:function:: const char* PyCapsule_GetName(PyObject *capsule) 88 89 Return the current name stored in the capsule. On failure, set an exception 90 and return *NULL*. 91 92 It is legal for a capsule to have a *NULL* name. This makes a *NULL* return 93 code somewhat ambiguous; use :c:func:`PyCapsule_IsValid` or 94 :c:func:`PyErr_Occurred` to disambiguate. 95 96 97 .. c:function:: void* PyCapsule_Import(const char *name, int no_block) 98 99 Import a pointer to a C object from a capsule attribute in a module. The 100 *name* parameter should specify the full name to the attribute, as in 101 ``module.attribute``. The *name* stored in the capsule must match this 102 string exactly. If *no_block* is true, import the module without blocking 103 (using :c:func:`PyImport_ImportModuleNoBlock`). If *no_block* is false, 104 import the module conventionally (using :c:func:`PyImport_ImportModule`). 105 106 Return the capsule's internal *pointer* on success. On failure, set an 107 exception and return *NULL*. However, if :c:func:`PyCapsule_Import` failed to 108 import the module, and *no_block* was true, no exception is set. 109 110 .. c:function:: int PyCapsule_IsValid(PyObject *capsule, const char *name) 111 112 Determines whether or not *capsule* is a valid capsule. A valid capsule is 113 non-*NULL*, passes :c:func:`PyCapsule_CheckExact`, has a non-*NULL* pointer 114 stored in it, and its internal name matches the *name* parameter. (See 115 :c:func:`PyCapsule_GetPointer` for information on how capsule names are 116 compared.) 117 118 In other words, if :c:func:`PyCapsule_IsValid` returns a true value, calls to 119 any of the accessors (any function starting with :c:func:`PyCapsule_Get`) are 120 guaranteed to succeed. 121 122 Return a nonzero value if the object is valid and matches the name passed in. 123 Return ``0`` otherwise. This function will not fail. 124 125 .. c:function:: int PyCapsule_SetContext(PyObject *capsule, void *context) 126 127 Set the context pointer inside *capsule* to *context*. 128 129 Return ``0`` on success. Return nonzero and set an exception on failure. 130 131 .. c:function:: int PyCapsule_SetDestructor(PyObject *capsule, PyCapsule_Destructor destructor) 132 133 Set the destructor inside *capsule* to *destructor*. 134 135 Return ``0`` on success. Return nonzero and set an exception on failure. 136 137 .. c:function:: int PyCapsule_SetName(PyObject *capsule, const char *name) 138 139 Set the name inside *capsule* to *name*. If non-*NULL*, the name must 140 outlive the capsule. If the previous *name* stored in the capsule was not 141 *NULL*, no attempt is made to free it. 142 143 Return ``0`` on success. Return nonzero and set an exception on failure. 144 145 .. c:function:: int PyCapsule_SetPointer(PyObject *capsule, void *pointer) 146 147 Set the void pointer inside *capsule* to *pointer*. The pointer may not be 148 *NULL*. 149 150 Return ``0`` on success. Return nonzero and set an exception on failure. 151
