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 .. versionadded:: 2.7 13 14 15 .. c:type:: PyCapsule 16 17 This subtype of :c:type:`PyObject` represents an opaque value, useful for C 18 extension modules who need to pass an opaque value (as a :c:type:`void\*` 19 pointer) through Python code to other C code. It is often used to make a C 20 function pointer defined in one module available to other modules, so the 21 regular import mechanism can be used to access C APIs defined in dynamically 22 loaded modules. 23 24 25 .. c:type:: PyCapsule_Destructor 26 27 The type of a destructor callback for a capsule. Defined as:: 28 29 typedef void (*PyCapsule_Destructor)(PyObject *); 30 31 See :c:func:`PyCapsule_New` for the semantics of PyCapsule_Destructor 32 callbacks. 33 34 35 .. c:function:: int PyCapsule_CheckExact(PyObject *p) 36 37 Return true if its argument is a :c:type:`PyCapsule`. 38 39 40 .. c:function:: PyObject* PyCapsule_New(void *pointer, const char *name, PyCapsule_Destructor destructor) 41 42 Create a :c:type:`PyCapsule` encapsulating the *pointer*. The *pointer* 43 argument may not be *NULL*. 44 45 On failure, set an exception and return *NULL*. 46 47 The *name* string may either be *NULL* or a pointer to a valid C string. If 48 non-*NULL*, this string must outlive the capsule. (Though it is permitted to 49 free it inside the *destructor*.) 50 51 If the *destructor* argument is not *NULL*, it will be called with the 52 capsule as its argument when it is destroyed. 53 54 If this capsule will be stored as an attribute of a module, the *name* should 55 be specified as ``modulename.attributename``. This will enable other modules 56 to import the capsule using :c:func:`PyCapsule_Import`. 57 58 59 .. c:function:: void* PyCapsule_GetPointer(PyObject *capsule, const char *name) 60 61 Retrieve the *pointer* stored in the capsule. On failure, set an exception 62 and return *NULL*. 63 64 The *name* parameter must compare exactly to the name stored in the capsule. 65 If the name stored in the capsule is *NULL*, the *name* passed in must also 66 be *NULL*. Python uses the C function :c:func:`strcmp` to compare capsule 67 names. 68 69 70 .. c:function:: PyCapsule_Destructor PyCapsule_GetDestructor(PyObject *capsule) 71 72 Return the current destructor stored in the capsule. On failure, set an 73 exception and return *NULL*. 74 75 It is legal for a capsule to have a *NULL* destructor. This makes a *NULL* 76 return code somewhat ambiguous; use :c:func:`PyCapsule_IsValid` or 77 :c:func:`PyErr_Occurred` to disambiguate. 78 79 80 .. c:function:: void* PyCapsule_GetContext(PyObject *capsule) 81 82 Return the current context stored in the capsule. On failure, set an 83 exception and return *NULL*. 84 85 It is legal for a capsule to have a *NULL* context. This makes a *NULL* 86 return code somewhat ambiguous; use :c:func:`PyCapsule_IsValid` or 87 :c:func:`PyErr_Occurred` to disambiguate. 88 89 90 .. c:function:: const char* PyCapsule_GetName(PyObject *capsule) 91 92 Return the current name stored in the capsule. On failure, set an exception 93 and return *NULL*. 94 95 It is legal for a capsule to have a *NULL* name. This makes a *NULL* return 96 code somewhat ambiguous; use :c:func:`PyCapsule_IsValid` or 97 :c:func:`PyErr_Occurred` to disambiguate. 98 99 100 .. c:function:: void* PyCapsule_Import(const char *name, int no_block) 101 102 Import a pointer to a C object from a capsule attribute in a module. The 103 *name* parameter should specify the full name to the attribute, as in 104 ``module.attribute``. The *name* stored in the capsule must match this 105 string exactly. If *no_block* is true, import the module without blocking 106 (using :c:func:`PyImport_ImportModuleNoBlock`). If *no_block* is false, 107 import the module conventionally (using :c:func:`PyImport_ImportModule`). 108 109 Return the capsule's internal *pointer* on success. On failure, set an 110 exception and return *NULL*. 111 112 113 .. c:function:: int PyCapsule_IsValid(PyObject *capsule, const char *name) 114 115 Determines whether or not *capsule* is a valid capsule. A valid capsule is 116 non-*NULL*, passes :c:func:`PyCapsule_CheckExact`, has a non-*NULL* pointer 117 stored in it, and its internal name matches the *name* parameter. (See 118 :c:func:`PyCapsule_GetPointer` for information on how capsule names are 119 compared.) 120 121 In other words, if :c:func:`PyCapsule_IsValid` returns a true value, calls to 122 any of the accessors (any function starting with :c:func:`PyCapsule_Get`) are 123 guaranteed to succeed. 124 125 Return a nonzero value if the object is valid and matches the name passed in. 126 Return ``0`` otherwise. This function will not fail. 127 128 129 .. c:function:: int PyCapsule_SetContext(PyObject *capsule, void *context) 130 131 Set the context pointer inside *capsule* to *context*. 132 133 Return ``0`` on success. Return nonzero and set an exception on failure. 134 135 136 .. c:function:: int PyCapsule_SetDestructor(PyObject *capsule, PyCapsule_Destructor destructor) 137 138 Set the destructor inside *capsule* to *destructor*. 139 140 Return ``0`` on success. Return nonzero and set an exception on failure. 141 142 143 .. c:function:: int PyCapsule_SetName(PyObject *capsule, const char *name) 144 145 Set the name inside *capsule* to *name*. If non-*NULL*, the name must 146 outlive the capsule. If the previous *name* stored in the capsule was not 147 *NULL*, no attempt is made to free it. 148 149 Return ``0`` on success. Return nonzero and set an exception on failure. 150 151 152 .. c:function:: int PyCapsule_SetPointer(PyObject *capsule, void *pointer) 153 154 Set the void pointer inside *capsule* to *pointer*. The pointer may not be 155 *NULL*. 156 157 Return ``0`` on success. Return nonzero and set an exception on failure. 158
