mirror of https://github.com/python/cpython
bpo-40521: Optimize PyBytes_FromStringAndSize(str, 0) (GH-21142)
Always create the empty bytes string singleton. Optimize PyBytes_FromStringAndSize(str, 0): it no longer has to check if the empty string singleton was created or not, it is always available. Add functions: * _PyBytes_Init() * bytes_get_empty(), bytes_new_empty() * bytes_create_empty_string_singleton() * unicode_create_empty_string_singleton() _Py_unicode_state: rename empty structure member to empty_string.
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@ -66,13 +66,13 @@ struct _Py_unicode_fs_codec {
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};
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struct _Py_bytes_state {
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PyObject *empty_string;
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PyBytesObject *characters[256];
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PyBytesObject *empty_string;
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};
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struct _Py_unicode_state {
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// The empty Unicode object is a singleton to improve performance.
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PyObject *empty;
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PyObject *empty_string;
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/* Single character Unicode strings in the Latin-1 range are being
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shared as well. */
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PyObject *latin1[256];
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@ -32,6 +32,7 @@ PyAPI_FUNC(int) _Py_IsLocaleCoercionTarget(const char *ctype_loc);
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/* Various one-time initializers */
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extern PyStatus _PyUnicode_Init(PyThreadState *tstate);
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extern PyStatus _PyBytes_Init(PyThreadState *tstate);
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extern int _PyStructSequence_Init(void);
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extern int _PyLong_Init(PyThreadState *tstate);
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extern PyStatus _PyTuple_Init(PyThreadState *tstate);
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@ -4,8 +4,9 @@
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#include "Python.h"
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#include "pycore_abstract.h" // _PyIndex_Check()
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#include "pycore_bytes_methods.h"
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#include "pycore_object.h"
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#include "pycore_bytes_methods.h" // _Py_bytes_startswith()
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#include "pycore_initconfig.h" // _PyStatus_OK()
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#include "pycore_object.h" // _PyObject_GC_TRACK
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#include "pycore_pymem.h" // PYMEM_CLEANBYTE
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#include "pystrhex.h"
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@ -41,6 +42,44 @@ get_bytes_state(void)
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}
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// Return a borrowed reference to the empty bytes string singleton.
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static inline PyObject* bytes_get_empty(void)
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{
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struct _Py_bytes_state *state = get_bytes_state();
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// bytes_get_empty() must not be called before _PyBytes_Init()
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// or after _PyBytes_Fini()
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assert(state->empty_string != NULL);
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return state->empty_string;
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}
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// Return a strong reference to the empty bytes string singleton.
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static inline PyObject* bytes_new_empty(void)
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{
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PyObject *empty = bytes_get_empty();
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Py_INCREF(empty);
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return (PyObject *)empty;
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}
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static int
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bytes_create_empty_string_singleton(struct _Py_bytes_state *state)
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{
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// Create the empty bytes string singleton
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PyBytesObject *op = (PyBytesObject *)PyObject_Malloc(PyBytesObject_SIZE);
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if (op == NULL) {
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return -1;
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}
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_PyObject_InitVar((PyVarObject*)op, &PyBytes_Type, 0);
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op->ob_shash = -1;
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op->ob_sval[0] = '\0';
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assert(state->empty_string == NULL);
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state->empty_string = (PyObject *)op;
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return 0;
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}
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/*
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For PyBytes_FromString(), the parameter `str' points to a null-terminated
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string containing exactly `size' bytes.
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@ -70,12 +109,7 @@ _PyBytes_FromSize(Py_ssize_t size, int use_calloc)
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assert(size >= 0);
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if (size == 0) {
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struct _Py_bytes_state *state = get_bytes_state();
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op = state->empty_string;
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if (op != NULL) {
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Py_INCREF(op);
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return (PyObject *)op;
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}
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return bytes_new_empty();
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}
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if ((size_t)size > (size_t)PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
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@ -94,13 +128,8 @@ _PyBytes_FromSize(Py_ssize_t size, int use_calloc)
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}
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_PyObject_InitVar((PyVarObject*)op, &PyBytes_Type, size);
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op->ob_shash = -1;
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if (!use_calloc)
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if (!use_calloc) {
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op->ob_sval[size] = '\0';
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/* empty byte string singleton */
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if (size == 0) {
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struct _Py_bytes_state *state = get_bytes_state();
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Py_INCREF(op);
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state->empty_string = op;
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}
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return (PyObject *) op;
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}
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@ -122,6 +151,9 @@ PyBytes_FromStringAndSize(const char *str, Py_ssize_t size)
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return (PyObject *)op;
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}
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}
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if (size == 0) {
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return bytes_new_empty();
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}
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op = (PyBytesObject *)_PyBytes_FromSize(size, 0);
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if (op == NULL)
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@ -155,11 +187,7 @@ PyBytes_FromString(const char *str)
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struct _Py_bytes_state *state = get_bytes_state();
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if (size == 0) {
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op = state->empty_string;
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if (op != NULL) {
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Py_INCREF(op);
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return (PyObject *)op;
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}
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return bytes_new_empty();
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}
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else if (size == 1) {
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op = state->characters[*str & UCHAR_MAX];
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@ -178,11 +206,8 @@ PyBytes_FromString(const char *str)
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op->ob_shash = -1;
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memcpy(op->ob_sval, str, size+1);
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/* share short strings */
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if (size == 0) {
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Py_INCREF(op);
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state->empty_string = op;
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}
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else if (size == 1) {
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if (size == 1) {
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assert(state->characters[*str & UCHAR_MAX] == NULL);
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Py_INCREF(op);
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state->characters[*str & UCHAR_MAX] = op;
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}
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@ -1272,7 +1297,7 @@ PyBytes_AsStringAndSize(PyObject *obj,
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/* -------------------------------------------------------------------- */
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/* Methods */
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#define STRINGLIB_GET_EMPTY() get_bytes_state()->empty_string
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#define STRINGLIB_GET_EMPTY() bytes_get_empty()
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#include "stringlib/stringdefs.h"
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@ -3053,9 +3078,9 @@ _PyBytes_Resize(PyObject **pv, Py_ssize_t newsize)
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goto error;
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}
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if (newsize == 0) {
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*pv = _PyBytes_FromSize(0, 0);
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*pv = bytes_new_empty();
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Py_DECREF(v);
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return (*pv == NULL) ? -1 : 0;
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return 0;
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}
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/* XXX UNREF/NEWREF interface should be more symmetrical */
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#ifdef Py_REF_DEBUG
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@ -3084,6 +3109,18 @@ error:
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return -1;
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}
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PyStatus
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_PyBytes_Init(PyThreadState *tstate)
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{
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struct _Py_bytes_state *state = &tstate->interp->bytes;
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if (bytes_create_empty_string_singleton(state) < 0) {
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return _PyStatus_NO_MEMORY();
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}
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return _PyStatus_OK();
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}
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void
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_PyBytes_Fini(PyThreadState *tstate)
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{
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@ -41,16 +41,15 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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#define PY_SSIZE_T_CLEAN
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#include "Python.h"
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#include "pycore_abstract.h" // _PyIndex_Check()
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#include "pycore_bytes_methods.h"
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#include "pycore_fileutils.h"
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#include "pycore_initconfig.h"
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#include "pycore_bytes_methods.h" // _Py_bytes_lower()
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#include "pycore_initconfig.h" // _PyStatus_OK()
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#include "pycore_interp.h" // PyInterpreterState.fs_codec
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#include "pycore_object.h"
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#include "pycore_pathconfig.h"
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#include "pycore_pylifecycle.h"
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#include "pycore_object.h" // _PyObject_GC_TRACK()
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#include "pycore_pathconfig.h" // _Py_DumpPathConfig()
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#include "pycore_pylifecycle.h" // _Py_SetFileSystemEncoding()
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#include "pycore_pystate.h" // _PyInterpreterState_GET()
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#include "ucnhash.h"
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#include "stringlib/eq.h"
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#include "ucnhash.h" // _PyUnicode_Name_CAPI
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#include "stringlib/eq.h" // unicode_eq()
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#ifdef MS_WINDOWS
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#include <windows.h>
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@ -236,10 +235,12 @@ static inline PyObject* unicode_get_empty(void)
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struct _Py_unicode_state *state = get_unicode_state();
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// unicode_get_empty() must not be called before _PyUnicode_Init()
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// or after _PyUnicode_Fini()
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assert(state->empty != NULL);
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return state->empty;
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assert(state->empty_string != NULL);
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return state->empty_string;
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}
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// Return a strong reference to the empty string singleton.
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static inline PyObject* unicode_new_empty(void)
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{
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PyObject *empty = unicode_get_empty();
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}
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#endif
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static int
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unicode_create_empty_string_singleton(struct _Py_unicode_state *state)
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{
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// Use size=1 rather than size=0, so PyUnicode_New(0, maxchar) can be
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// optimized to always use state->empty_string without having to check if
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// it is NULL or not.
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PyObject *empty = PyUnicode_New(1, 0);
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if (empty == NULL) {
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return -1;
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}
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PyUnicode_1BYTE_DATA(empty)[0] = 0;
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_PyUnicode_LENGTH(empty) = 0;
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assert(_PyUnicode_CheckConsistency(empty, 1));
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assert(state->empty_string == NULL);
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state->empty_string = empty;
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return 0;
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}
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PyObject *
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PyUnicode_New(Py_ssize_t size, Py_UCS4 maxchar)
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{
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unicode_is_singleton(PyObject *unicode)
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{
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struct _Py_unicode_state *state = get_unicode_state();
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if (unicode == state->empty) {
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if (unicode == state->empty_string) {
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return 1;
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}
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PyASCIIObject *ascii = (PyASCIIObject *)unicode;
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@ -15542,20 +15563,10 @@ _PyUnicode_Init(PyThreadState *tstate)
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0x2029, /* PARAGRAPH SEPARATOR */
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};
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// Use size=1 rather than size=0, so PyUnicode_New(0, maxchar) can be
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// optimized to always use state->empty without having to check if it is
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// NULL or not.
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PyObject *empty = PyUnicode_New(1, 0);
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if (empty == NULL) {
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struct _Py_unicode_state *state = &tstate->interp->unicode;
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if (unicode_create_empty_string_singleton(state) < 0) {
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return _PyStatus_NO_MEMORY();
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}
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PyUnicode_1BYTE_DATA(empty)[0] = 0;
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_PyUnicode_LENGTH(empty) = 0;
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assert(_PyUnicode_CheckConsistency(empty, 1));
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struct _Py_unicode_state *state = &tstate->interp->unicode;
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assert(state->empty == NULL);
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state->empty = empty;
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if (_Py_IsMainInterpreter(tstate)) {
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/* initialize the linebreak bloom filter */
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#endif /* __INSURE__ */
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}
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Py_CLEAR(state->empty);
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Py_CLEAR(state->empty_string);
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for (Py_ssize_t i = 0; i < 256; i++) {
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Py_CLEAR(state->latin1[i]);
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return status;
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}
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status = _PyBytes_Init(tstate);
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if (_PyStatus_EXCEPTION(status)) {
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return status;
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}
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status = _PyExc_Init(tstate);
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if (_PyStatus_EXCEPTION(status)) {
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return status;
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