Objects/capsule.c

   1 /* Wrap void * pointers to be passed between C modules */
   2
   3 #include "Python.h"
   4
   5 /* Internal structure of PyCapsule */
   6 typedef struct {
   7     PyObject_HEAD
   8     void *pointer;
   9     const char *name;
  10     void *context;
  11     PyCapsule_Destructor destructor;
  12 } PyCapsule;
  13
  14
  15
  16 static int
  17 _is_legal_capsule(PyCapsule *capsule, const char *invalid_capsule)
  18 {
  19     if (!capsule || !PyCapsule_CheckExact(capsule) || capsule->pointer == NULL) {
  20         PyErr_SetString(PyExc_ValueError, invalid_capsule);
  21         return 0;
  22     }
  23     return 1;
  24 }
  25
  26 #define is_legal_capsule(capsule, name) \
  27     (_is_legal_capsule(capsule, \
  28      name " called with invalid PyCapsule object"))
  29
  30
  31 static int
  32 name_matches(const char *name1, const char *name2) {
  33     /* if either is NULL, */
  34     if (!name1 || !name2) {
  35         /* they're only the same if they're both NULL. */
  36         return name1 == name2;
  37     }
  38     return !strcmp(name1, name2);
  39 }
  40
  41
  42
  43 PyObject *
  44 PyCapsule_New(void *pointer, const char *name, PyCapsule_Destructor destructor)
  45 {
  46     PyCapsule *capsule;
  47
  48     if (!pointer) {
  49         PyErr_SetString(PyExc_ValueError, "PyCapsule_New called with null pointer");
  50         return NULL;
  51     }
  52
  53     capsule = PyObject_NEW(PyCapsule, &PyCapsule_Type);
  54     if (capsule == NULL) {
  55         return NULL;
  56     }
  57
  58     capsule->pointer = pointer;
  59     capsule->name = name;
  60     capsule->context = NULL;
  61     capsule->destructor = destructor;
  62
  63     return (PyObject *)capsule;
  64 }
  65
  66
  67 int
  68 PyCapsule_IsValid(PyObject *o, const char *name)
  69 {
  70     PyCapsule *capsule = (PyCapsule *)o;
  71
  72     return (capsule != NULL &&
  73             PyCapsule_CheckExact(capsule) &&
  74             capsule->pointer != NULL &&
  75             name_matches(capsule->name, name));
  76 }
  77
  78
  79 void *
  80 PyCapsule_GetPointer(PyObject *o, const char *name)
  81 {
  82     PyCapsule *capsule = (PyCapsule *)o;
  83
  84     if (!is_legal_capsule(capsule, "PyCapsule_GetPointer")) {
  85         return NULL;
  86     }
  87
  88     if (!name_matches(name, capsule->name)) {
  89         PyErr_SetString(PyExc_ValueError, "PyCapsule_GetPointer called with incorrect name");
  90         return NULL;
  91     }
  92
  93     return capsule->pointer;
  94 }
  95
  96
  97 const char *
  98 PyCapsule_GetName(PyObject *o)
  99 {
 100     PyCapsule *capsule = (PyCapsule *)o;
 101
 102     if (!is_legal_capsule(capsule, "PyCapsule_GetName")) {
 103         return NULL;
 104     }
 105     return capsule->name;
 106 }
 107
 108
 109 PyCapsule_Destructor
 110 PyCapsule_GetDestructor(PyObject *o)
 111 {
 112     PyCapsule *capsule = (PyCapsule *)o;
 113
 114     if (!is_legal_capsule(capsule, "PyCapsule_GetDestructor")) {
 115         return NULL;
 116     }
 117     return capsule->destructor;
 118 }
 119
 120
 121 void *
 122 PyCapsule_GetContext(PyObject *o)
 123 {
 124     PyCapsule *capsule = (PyCapsule *)o;
 125
 126     if (!is_legal_capsule(capsule, "PyCapsule_GetContext")) {
 127         return NULL;
 128     }
 129     return capsule->context;
 130 }
 131
 132
 133 int
 134 PyCapsule_SetPointer(PyObject *o, void *pointer)
 135 {
 136     PyCapsule *capsule = (PyCapsule *)o;
 137
 138     if (!pointer) {
 139         PyErr_SetString(PyExc_ValueError, "PyCapsule_SetPointer called with null pointer");
 140         return -1;
 141     }
 142
 143     if (!is_legal_capsule(capsule, "PyCapsule_SetPointer")) {
 144         return -1;
 145     }
 146
 147     capsule->pointer = pointer;
 148     return 0;
 149 }
 150
 151
 152 int
 153 PyCapsule_SetName(PyObject *o, const char *name)
 154 {
 155     PyCapsule *capsule = (PyCapsule *)o;
 156
 157     if (!is_legal_capsule(capsule, "PyCapsule_SetName")) {
 158         return -1;
 159     }
 160
 161     capsule->name = name;
 162     return 0;
 163 }
 164
 165
 166 int
 167 PyCapsule_SetDestructor(PyObject *o, PyCapsule_Destructor destructor)
 168 {
 169     PyCapsule *capsule = (PyCapsule *)o;
 170
 171     if (!is_legal_capsule(capsule, "PyCapsule_SetDestructor")) {
 172         return -1;
 173     }
 174
 175     capsule->destructor = destructor;
 176     return 0;
 177 }
 178
 179
 180 int
 181 PyCapsule_SetContext(PyObject *o, void *context)
 182 {
 183     PyCapsule *capsule = (PyCapsule *)o;
 184
 185     if (!is_legal_capsule(capsule, "PyCapsule_SetContext")) {
 186         return -1;
 187     }
 188
 189     capsule->context = context;
 190     return 0;
 191 }
 192
 193
 194 void *
 195 PyCapsule_Import(const char *name, int no_block)
 196 {
 197     PyObject *object = NULL;
 198     void *return_value = NULL;
 199     char *trace;
 200     size_t name_length = (strlen(name) + 1) * sizeof(char);
 201     char *name_dup = (char *)PyMem_MALLOC(name_length);
 202
 203     if (!name_dup) {
 204         return NULL;
 205     }
 206
 207     memcpy(name_dup, name, name_length);
 208
 209     trace = name_dup;
 210     while (trace) {
 211         char *dot = strchr(trace, '.');
 212         if (dot) {
 213             *dot++ = '\0';
 214         }
 215
 216         if (object == NULL) {
 217             if (no_block) {
 218                 object = PyImport_ImportModuleNoBlock(trace);
 219             } else {
 220                 object = PyImport_ImportModule(trace);
 221                 if (!object) {
 222                     PyErr_Format(PyExc_ImportError, "PyCapsule_Import could not import module \"%s\"", trace);
 223                 }
 224             }
 225         } else {
 226             PyObject *object2 = PyObject_GetAttrString(object, trace);
 227             Py_DECREF(object);
 228             object = object2;
 229         }
 230         if (!object) {
 231             goto EXIT;
 232         }
 233
 234         trace = dot;
 235     }
 236
 237     /* compare attribute name to module.name by hand */
 238     if (PyCapsule_IsValid(object, name)) {
 239         PyCapsule *capsule = (PyCapsule *)object;
 240         return_value = capsule->pointer;
 241     } else {
 242         PyErr_Format(PyExc_AttributeError,
 243             "PyCapsule_Import \"%s\" is not valid",
 244             name);
 245     }
 246
 247 EXIT:
 248     Py_XDECREF(object);
 249     if (name_dup) {
 250         PyMem_FREE(name_dup);
 251     }
 252     return return_value;
 253 }
 254
 255
 256 static void
 257 capsule_dealloc(PyObject *o)
 258 {
 259     PyCapsule *capsule = (PyCapsule *)o;
 260     if (capsule->destructor) {
 261         capsule->destructor(o);
 262     }
 263     PyObject_DEL(o);
 264 }
 265
 266
 267 static PyObject *
 268 capsule_repr(PyObject *o)
 269 {
 270     PyCapsule *capsule = (PyCapsule *)o;
 271     const char *name;
 272     const char *quote;
 273
 274     if (capsule->name) {
 275         quote = "\"";
 276         name = capsule->name;
 277     } else {
 278         quote = "";
 279         name = "NULL";
 280     }
 281
 282     return PyString_FromFormat("<capsule object %s%s%s at %p>",
 283         quote, name, quote, capsule);
 284 }
 285
 286
 287
 288 PyDoc_STRVAR(PyCapsule_Type__doc__,
 289 "Capsule objects let you wrap a C \"void *\" pointer in a Python\n\
 290 object.  They're a way of passing data through the Python interpreter\n\
 291 without creating your own custom type.\n\
 292 \n\
 293 Capsules are used for communication between extension modules.\n\
 294 They provide a way for an extension module to export a C interface\n\
 295 to other extension modules, so that extension modules can use the\n\
 296 Python import mechanism to link to one another.\n\
 297 ");
 298
 299 PyTypeObject PyCapsule_Type = {
 300     PyVarObject_HEAD_INIT(&PyType_Type, 0)
 301     "PyCapsule",                /*tp_name*/
 302     sizeof(PyCapsule),          /*tp_basicsize*/
 303     0,                          /*tp_itemsize*/
 304     /* methods */
 305     capsule_dealloc, /*tp_dealloc*/
 306     0,                          /*tp_print*/
 307     0,                          /*tp_getattr*/
 308     0,                          /*tp_setattr*/
 309     0,                          /*tp_reserved*/
 310     capsule_repr, /*tp_repr*/
 311     0,                          /*tp_as_number*/
 312     0,                          /*tp_as_sequence*/
 313     0,                          /*tp_as_mapping*/
 314     0,                          /*tp_hash*/
 315     0,                          /*tp_call*/
 316     0,                          /*tp_str*/
 317     0,                          /*tp_getattro*/
 318     0,                          /*tp_setattro*/
 319     0,                          /*tp_as_buffer*/
 320     0,                          /*tp_flags*/
 321     PyCapsule_Type__doc__       /*tp_doc*/
 322 };
 323
 324