| 1 |
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| 2 | /* String object interface */
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| 3 |
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| 4 | #ifndef Py_STRINGOBJECT_H
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| 5 | #define Py_STRINGOBJECT_H
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| 6 | #ifdef __cplusplus
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| 7 | extern "C" {
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| 8 | #endif
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| 9 |
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| 10 | #include <stdarg.h>
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| 11 |
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| 12 | /*
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| 13 | Type PyStringObject represents a character string. An extra zero byte is
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| 14 | reserved at the end to ensure it is zero-terminated, but a size is
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| 15 | present so strings with null bytes in them can be represented. This
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| 16 | is an immutable object type.
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| 17 |
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| 18 | There are functions to create new string objects, to test
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| 19 | an object for string-ness, and to get the
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| 20 | string value. The latter function returns a null pointer
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| 21 | if the object is not of the proper type.
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| 22 | There is a variant that takes an explicit size as well as a
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| 23 | variant that assumes a zero-terminated string. Note that none of the
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| 24 | functions should be applied to nil objects.
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| 25 | */
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| 26 |
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| 27 | /* Caching the hash (ob_shash) saves recalculation of a string's hash value.
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| 28 | Interning strings (ob_sstate) tries to ensure that only one string
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| 29 | object with a given value exists, so equality tests can be one pointer
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| 30 | comparison. This is generally restricted to strings that "look like"
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| 31 | Python identifiers, although the intern() builtin can be used to force
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| 32 | interning of any string.
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| 33 | Together, these sped the interpreter by up to 20%. */
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| 34 |
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| 35 | typedef struct {
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| 36 | PyObject_VAR_HEAD
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| 37 | long ob_shash;
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| 38 | int ob_sstate;
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| 39 | char ob_sval[1];
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| 40 |
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| 41 | /* Invariants:
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| 42 | * ob_sval contains space for 'ob_size+1' elements.
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| 43 | * ob_sval[ob_size] == 0.
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| 44 | * ob_shash is the hash of the string or -1 if not computed yet.
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| 45 | * ob_sstate != 0 iff the string object is in stringobject.c's
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| 46 | * 'interned' dictionary; in this case the two references
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| 47 | * from 'interned' to this object are *not counted* in ob_refcnt.
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| 48 | */
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