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132 lines
5.2 KiB
132 lines
5.2 KiB
#ifndef Py_DICTOBJECT_H |
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#define Py_DICTOBJECT_H |
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#ifdef __cplusplus |
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extern "C" { |
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#endif |
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/* Dictionary object type -- mapping from hashable object to object */ |
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/* The distribution includes a separate file, Objects/dictnotes.txt, |
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describing explorations into dictionary design and optimization. |
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It covers typical dictionary use patterns, the parameters for |
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tuning dictionaries, and several ideas for possible optimizations. |
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*/ |
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/* |
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There are three kinds of slots in the table: |
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1. Unused. me_key == me_value == NULL |
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Does not hold an active (key, value) pair now and never did. Unused can |
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transition to Active upon key insertion. This is the only case in which |
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me_key is NULL, and is each slot's initial state. |
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2. Active. me_key != NULL and me_key != dummy and me_value != NULL |
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Holds an active (key, value) pair. Active can transition to Dummy upon |
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key deletion. This is the only case in which me_value != NULL. |
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3. Dummy. me_key == dummy and me_value == NULL |
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Previously held an active (key, value) pair, but that was deleted and an |
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active pair has not yet overwritten the slot. Dummy can transition to |
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Active upon key insertion. Dummy slots cannot be made Unused again |
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(cannot have me_key set to NULL), else the probe sequence in case of |
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collision would have no way to know they were once active. |
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Note: .popitem() abuses the me_hash field of an Unused or Dummy slot to |
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hold a search finger. The me_hash field of Unused or Dummy slots has no |
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meaning otherwise. |
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*/ |
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/* PyDict_MINSIZE is the minimum size of a dictionary. This many slots are |
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* allocated directly in the dict object (in the ma_smalltable member). |
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* It must be a power of 2, and at least 4. 8 allows dicts with no more |
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* than 5 active entries to live in ma_smalltable (and so avoid an |
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* additional malloc); instrumentation suggested this suffices for the |
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* majority of dicts (consisting mostly of usually-small instance dicts and |
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* usually-small dicts created to pass keyword arguments). |
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*/ |
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#define PyDict_MINSIZE 8 |
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typedef struct { |
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long me_hash; /* cached hash code of me_key */ |
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PyObject *me_key; |
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PyObject *me_value; |
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} PyDictEntry; |
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/* |
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To ensure the lookup algorithm terminates, there must be at least one Unused |
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slot (NULL key) in the table. |
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The value ma_fill is the number of non-NULL keys (sum of Active and Dummy); |
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ma_used is the number of non-NULL, non-dummy keys (== the number of non-NULL |
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values == the number of Active items). |
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To avoid slowing down lookups on a near-full table, we resize the table when |
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it's two-thirds full. |
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*/ |
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typedef struct _dictobject PyDictObject; |
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struct _dictobject { |
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PyObject_HEAD |
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int ma_fill; /* # Active + # Dummy */ |
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int ma_used; /* # Active */ |
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/* The table contains ma_mask + 1 slots, and that's a power of 2. |
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* We store the mask instead of the size because the mask is more |
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* frequently needed. |
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*/ |
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int ma_mask; |
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/* ma_table points to ma_smalltable for small tables, else to |
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* additional malloc'ed memory. ma_table is never NULL! This rule |
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* saves repeated runtime null-tests in the workhorse getitem and |
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* setitem calls. |
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*/ |
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PyDictEntry *ma_table; |
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PyDictEntry *(*ma_lookup)(PyDictObject *mp, PyObject *key, long hash); |
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PyDictEntry ma_smalltable[PyDict_MINSIZE]; |
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}; |
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PyAPI_DATA(PyTypeObject) PyDict_Type; |
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#define PyDict_Check(op) PyObject_TypeCheck(op, &PyDict_Type) |
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PyAPI_FUNC(PyObject *) PyDict_New(void); |
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PyAPI_FUNC(PyObject *) PyDict_GetItem(PyObject *mp, PyObject *key); |
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PyAPI_FUNC(int) PyDict_SetItem(PyObject *mp, PyObject *key, PyObject *item); |
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PyAPI_FUNC(int) PyDict_DelItem(PyObject *mp, PyObject *key); |
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PyAPI_FUNC(void) PyDict_Clear(PyObject *mp); |
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PyAPI_FUNC(int) PyDict_Next( |
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PyObject *mp, int *pos, PyObject **key, PyObject **value); |
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PyAPI_FUNC(PyObject *) PyDict_Keys(PyObject *mp); |
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PyAPI_FUNC(PyObject *) PyDict_Values(PyObject *mp); |
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PyAPI_FUNC(PyObject *) PyDict_Items(PyObject *mp); |
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PyAPI_FUNC(int) PyDict_Size(PyObject *mp); |
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PyAPI_FUNC(PyObject *) PyDict_Copy(PyObject *mp); |
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/* PyDict_Update(mp, other) is equivalent to PyDict_Merge(mp, other, 1). */ |
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PyAPI_FUNC(int) PyDict_Update(PyObject *mp, PyObject *other); |
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/* PyDict_Merge updates/merges from a mapping object (an object that |
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supports PyMapping_Keys() and PyObject_GetItem()). If override is true, |
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the last occurrence of a key wins, else the first. The Python |
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dict.update(other) is equivalent to PyDict_Merge(dict, other, 1). |
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*/ |
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PyAPI_FUNC(int) PyDict_Merge(PyObject *mp, |
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PyObject *other, |
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int override); |
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/* PyDict_MergeFromSeq2 updates/merges from an iterable object producing |
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iterable objects of length 2. If override is true, the last occurrence |
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of a key wins, else the first. The Python dict constructor dict(seq2) |
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is equivalent to dict={}; PyDict_MergeFromSeq(dict, seq2, 1). |
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*/ |
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PyAPI_FUNC(int) PyDict_MergeFromSeq2(PyObject *d, |
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PyObject *seq2, |
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int override); |
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PyAPI_FUNC(PyObject *) PyDict_GetItemString(PyObject *dp, const char *key); |
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PyAPI_FUNC(int) PyDict_SetItemString(PyObject *dp, const char *key, PyObject *item); |
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PyAPI_FUNC(int) PyDict_DelItemString(PyObject *dp, const char *key); |
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#ifdef __cplusplus |
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} |
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#endif |
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#endif /* !Py_DICTOBJECT_H */
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