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/Include/internal/pycore_interp.h b/Include/internal/pycore_interp.h
index bf1769e..cfc2747 100644
--- a/Include/internal/pycore_interp.h
+++ b/Include/internal/pycore_interp.h
@@ -66,13 +66,13 @@
};
struct _Py_bytes_state {
+ PyObject *empty_string;
PyBytesObject *characters[256];
- PyBytesObject *empty_string;
};
struct _Py_unicode_state {
// The empty Unicode object is a singleton to improve performance.
- PyObject *empty;
+ PyObject *empty_string;
/* Single character Unicode strings in the Latin-1 range are being
shared as well. */
PyObject *latin1[256];
diff --git a/Include/internal/pycore_pylifecycle.h b/Include/internal/pycore_pylifecycle.h
index 3b21737..bffc95b 100644
--- a/Include/internal/pycore_pylifecycle.h
+++ b/Include/internal/pycore_pylifecycle.h
@@ -32,6 +32,7 @@
/* Various one-time initializers */
extern PyStatus _PyUnicode_Init(PyThreadState *tstate);
+extern PyStatus _PyBytes_Init(PyThreadState *tstate);
extern int _PyStructSequence_Init(void);
extern int _PyLong_Init(PyThreadState *tstate);
extern PyStatus _PyTuple_Init(PyThreadState *tstate);
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index ce006e1..782bc8e 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -4,8 +4,9 @@
#include "Python.h"
#include "pycore_abstract.h" // _PyIndex_Check()
-#include "pycore_bytes_methods.h"
-#include "pycore_object.h"
+#include "pycore_bytes_methods.h" // _Py_bytes_startswith()
+#include "pycore_initconfig.h" // _PyStatus_OK()
+#include "pycore_object.h" // _PyObject_GC_TRACK
#include "pycore_pymem.h" // PYMEM_CLEANBYTE
#include "pystrhex.h"
@@ -41,6 +42,44 @@
}
+// Return a borrowed reference to the empty bytes string singleton.
+static inline PyObject* bytes_get_empty(void)
+{
+ struct _Py_bytes_state *state = get_bytes_state();
+ // bytes_get_empty() must not be called before _PyBytes_Init()
+ // or after _PyBytes_Fini()
+ assert(state->empty_string != NULL);
+ return state->empty_string;
+}
+
+
+// Return a strong reference to the empty bytes string singleton.
+static inline PyObject* bytes_new_empty(void)
+{
+ PyObject *empty = bytes_get_empty();
+ Py_INCREF(empty);
+ return (PyObject *)empty;
+}
+
+
+static int
+bytes_create_empty_string_singleton(struct _Py_bytes_state *state)
+{
+ // Create the empty bytes string singleton
+ PyBytesObject *op = (PyBytesObject *)PyObject_Malloc(PyBytesObject_SIZE);
+ if (op == NULL) {
+ return -1;
+ }
+ _PyObject_InitVar((PyVarObject*)op, &PyBytes_Type, 0);
+ op->ob_shash = -1;
+ op->ob_sval[0] = '\0';
+
+ assert(state->empty_string == NULL);
+ state->empty_string = (PyObject *)op;
+ return 0;
+}
+
+
/*
For PyBytes_FromString(), the parameter `str' points to a null-terminated
string containing exactly `size' bytes.
@@ -70,12 +109,7 @@
assert(size >= 0);
if (size == 0) {
- struct _Py_bytes_state *state = get_bytes_state();
- op = state->empty_string;
- if (op != NULL) {
- Py_INCREF(op);
- return (PyObject *)op;
- }
+ return bytes_new_empty();
}
if ((size_t)size > (size_t)PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
@@ -94,13 +128,8 @@
}
_PyObject_InitVar((PyVarObject*)op, &PyBytes_Type, size);
op->ob_shash = -1;
- if (!use_calloc)
+ if (!use_calloc) {
op->ob_sval[size] = '\0';
- /* empty byte string singleton */
- if (size == 0) {
- struct _Py_bytes_state *state = get_bytes_state();
- Py_INCREF(op);
- state->empty_string = op;
}
return (PyObject *) op;
}
@@ -122,6 +151,9 @@
return (PyObject *)op;
}
}
+ if (size == 0) {
+ return bytes_new_empty();
+ }
op = (PyBytesObject *)_PyBytes_FromSize(size, 0);
if (op == NULL)
@@ -155,11 +187,7 @@
struct _Py_bytes_state *state = get_bytes_state();
if (size == 0) {
- op = state->empty_string;
- if (op != NULL) {
- Py_INCREF(op);
- return (PyObject *)op;
- }
+ return bytes_new_empty();
}
else if (size == 1) {
op = state->characters[*str & UCHAR_MAX];
@@ -178,11 +206,8 @@
op->ob_shash = -1;
memcpy(op->ob_sval, str, size+1);
/* share short strings */
- if (size == 0) {
- Py_INCREF(op);
- state->empty_string = op;
- }
- else if (size == 1) {
+ if (size == 1) {
+ assert(state->characters[*str & UCHAR_MAX] == NULL);
Py_INCREF(op);
state->characters[*str & UCHAR_MAX] = op;
}
@@ -1272,7 +1297,7 @@
/* -------------------------------------------------------------------- */
/* Methods */
-#define STRINGLIB_GET_EMPTY() get_bytes_state()->empty_string
+#define STRINGLIB_GET_EMPTY() bytes_get_empty()
#include "stringlib/stringdefs.h"
@@ -3053,9 +3078,9 @@
goto error;
}
if (newsize == 0) {
- *pv = _PyBytes_FromSize(0, 0);
+ *pv = bytes_new_empty();
Py_DECREF(v);
- return (*pv == NULL) ? -1 : 0;
+ return 0;
}
/* XXX UNREF/NEWREF interface should be more symmetrical */
#ifdef Py_REF_DEBUG
@@ -3084,6 +3109,18 @@
return -1;
}
+
+PyStatus
+_PyBytes_Init(PyThreadState *tstate)
+{
+ struct _Py_bytes_state *state = &tstate->interp->bytes;
+ if (bytes_create_empty_string_singleton(state) < 0) {
+ return _PyStatus_NO_MEMORY();
+ }
+ return _PyStatus_OK();
+}
+
+
void
_PyBytes_Fini(PyThreadState *tstate)
{
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]);
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 4b658f8..cd993ea 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -607,6 +607,11 @@
return status;
}
+ status = _PyBytes_Init(tstate);
+ if (_PyStatus_EXCEPTION(status)) {
+ return status;
+ }
+
status = _PyExc_Init(tstate);
if (_PyStatus_EXCEPTION(status)) {
return status;