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bpo-40521: Optimize PyBytes_FromStringAndSize(str, 0) (GH-21142)

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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.
This commit is contained in:
Victor Stinner 2020-06-25 14:07:40 +02:00 • committed by GitHub
parent 0f8ec1fff0
commit 91698d8caa
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5 changed files with 107 additions and 53 deletions
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59
Objects/unicodeobject.c
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@ -41,16 +41,15 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#define PY_SSIZE_T_CLEAN
#include "Python.h"
#include "pycore_abstract.h" // _PyIndex_Check()
#include "pycore_bytes_methods.h"
#include "pycore_fileutils.h"
#include "pycore_initconfig.h"
#include "pycore_bytes_methods.h" // _Py_bytes_lower()
#include "pycore_initconfig.h" // _PyStatus_OK()
#include "pycore_interp.h" // PyInterpreterState.fs_codec
#include "pycore_object.h"
#include "pycore_pathconfig.h"
#include "pycore_pylifecycle.h"
#include "pycore_object.h" // _PyObject_GC_TRACK()
#include "pycore_pathconfig.h" // _Py_DumpPathConfig()
#include "pycore_pylifecycle.h" // _Py_SetFileSystemEncoding()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "ucnhash.h"
#include "stringlib/eq.h"
#include "ucnhash.h" // _PyUnicode_Name_CAPI
#include "stringlib/eq.h" // unicode_eq()
#ifdef MS_WINDOWS
#include <windows.h>
@ -236,10 +235,12 @@ static inline PyObject* unicode_get_empty(void)
struct _Py_unicode_state *state = get_unicode_state();
// unicode_get_empty() must not be called before _PyUnicode_Init()
// or after _PyUnicode_Fini()
assert(state->empty != NULL);
return state->empty;
assert(state->empty_string != NULL);
return state->empty_string;
}
// Return a strong reference to the empty string singleton.
static inline PyObject* unicode_new_empty(void)
{
PyObject *empty = unicode_get_empty();
@ -1385,6 +1386,26 @@ _PyUnicode_Dump(PyObject *op)
}
#endif
static int
unicode_create_empty_string_singleton(struct _Py_unicode_state *state)
{
// Use size=1 rather than size=0, so PyUnicode_New(0, maxchar) can be
// optimized to always use state->empty_string without having to check if
// it is NULL or not.
PyObject *empty = PyUnicode_New(1, 0);
if (empty == NULL) {
return -1;
}
PyUnicode_1BYTE_DATA(empty)[0] = 0;
_PyUnicode_LENGTH(empty) = 0;
assert(_PyUnicode_CheckConsistency(empty, 1));
assert(state->empty_string == NULL);
state->empty_string = empty;
return 0;
}
PyObject *
PyUnicode_New(Py_ssize_t size, Py_UCS4 maxchar)
{
@ -1972,7 +1993,7 @@ static int
unicode_is_singleton(PyObject *unicode)
{
struct _Py_unicode_state *state = get_unicode_state();
if (unicode == state->empty) {
if (unicode == state->empty_string) {
return 1;
}
PyASCIIObject *ascii = (PyASCIIObject *)unicode;
@ -15542,20 +15563,10 @@ _PyUnicode_Init(PyThreadState *tstate)
0x2029, /* PARAGRAPH SEPARATOR */
};
// Use size=1 rather than size=0, so PyUnicode_New(0, maxchar) can be
// optimized to always use state->empty without having to check if it is
// NULL or not.
PyObject *empty = PyUnicode_New(1, 0);
if (empty == NULL) {
struct _Py_unicode_state *state = &tstate->interp->unicode;
if (unicode_create_empty_string_singleton(state) < 0) {
return _PyStatus_NO_MEMORY();
}
PyUnicode_1BYTE_DATA(empty)[0] = 0;
_PyUnicode_LENGTH(empty) = 0;
assert(_PyUnicode_CheckConsistency(empty, 1));
struct _Py_unicode_state *state = &tstate->interp->unicode;
assert(state->empty == NULL);
state->empty = empty;
if (_Py_IsMainInterpreter(tstate)) {
/* initialize the linebreak bloom filter */
@ -16223,7 +16234,7 @@ _PyUnicode_Fini(PyThreadState *tstate)
#endif /* __INSURE__ */
}
Py_CLEAR(state->empty);
Py_CLEAR(state->empty_string);
for (Py_ssize_t i = 0; i < 256; i++) {
Py_CLEAR(state->latin1[i]);