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.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 5ba9951..55c8867 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -41,16 +41,15 @@
#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 @@
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 @@
}
#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 @@
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 @@
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 @@
#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]);