Python中的字符串对象(Python 源码剖析第三章)

时间：2010-11-12 来源：Ray Z

PyString_FromString 1 PyObject*　PyString_FromString(const char *str)
2 {
3     register size_t size;
4     register PyStringObject *op;
5
6     assert(str != NULL);
7     size = strlen(str);
8     if (size > PY_SSIZE_T_MAX - PyStringObject_SIZE) {
9         PyErr_SetString(PyExc_OverflowError,
10             "string is too long for a Python string");
11         return NULL;
12     }
13     if (size == 0 && (op = nullstring) != NULL) {
14 #ifdef COUNT_ALLOCS
15         null_strings++;
16 #endif
17         Py_INCREF(op);
18         return (PyObject *)op;
19     }
20     if (size == 1 && (op = characters[*str & UCHAR_MAX]) != NULL) {
21 #ifdef COUNT_ALLOCS
22         one_strings++;
23 #endif
24         Py_INCREF(op);
25         return (PyObject *)op;
26     }
27
28     /* Inline PyObject_NewVar */
29     op = (PyStringObject *)PyObject_MALLOC(PyStringObject_SIZE + size);
30     if (op == NULL)
31         return PyErr_NoMemory();
32     PyObject_INIT_VAR(op, &PyString_Type, size);
33     op->ob_shash = -1;
34     op->ob_sstate = SSTATE_NOT_INTERNED;
35     Py_MEMCPY(op->ob_sval, str, size+1);
36     /* share short strings */
37     if (size == 0) {
38         PyObject *t = (PyObject *)op;
39         PyString_InternInPlace(&t);
40         op = (PyStringObject *)t;
41         nullstring = op;
42         Py_INCREF(op);
43     } else if (size == 1) {
44         PyObject *t = (PyObject *)op;
45         PyString_InternInPlace(&t);
46         op = (PyStringObject *)t;
47         characters[*str & UCHAR_MAX] = op;
48         Py_INCREF(op);
49     }
50     return (PyObject *) op;
51 }