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Issue #4445: save 3 bytes of memory (on average) per bytes allocation. 

(This is a forward port of r67601).
This commit is contained in:
Mark Dickinson 2008-12-06 15:33:31 +00:00
parent 17fe364b44
commit fd24b323f9
2 changed files with 23 additions and 10 deletions
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5
Misc/NEWS
View File

@ -12,6 +12,11 @@ What's New in Python 3.1 alpha 0
Core and Builtins
-----------------
- Issue #4445: Replace "sizeof(PyBytesObject)" with
"offsetof(PyBytesObject, ob_sval) + 1" when allocating memory for
bytes instances. On a typical machine this saves 3 bytes of memory
(on average) per allocation of a bytes instance.
- Issue #4533: File read operation was dreadfully slow due to a slowly
growing read buffer. Fixed by using the same growth rate algorithm as
Python 2.x.

28
Objects/bytesobject.c
View File

@ -5,6 +5,7 @@
#include "Python.h"
#include "bytes_methods.h"
#include <stddef.h>
static Py_ssize_t
_getbuffer(PyObject *obj, Py_buffer *view)
@ -31,6 +32,14 @@ int null_strings, one_strings;
static PyBytesObject *characters[UCHAR_MAX + 1];
static PyBytesObject *nullstring;
/* PyBytesObject_SIZE gives the basic size of a string; any memory allocation
for a string of length n should request PyBytesObject_SIZE + n bytes.
Using PyBytesObject_SIZE instead of sizeof(PyBytesObject) saves
3 bytes per string allocation on a typical system.
*/
#define PyBytesObject_SIZE (offsetof(PyBytesObject, ob_sval) + 1)
/*
For both PyBytes_FromString() and PyBytes_FromStringAndSize(), the
parameter `size' denotes number of characters to allocate, not counting any
@ -83,14 +92,14 @@ PyBytes_FromStringAndSize(const char *str, Py_ssize_t size)
return (PyObject *)op;
}
if (size > PY_SSIZE_T_MAX - sizeof(PyBytesObject)) {
if (size > PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
PyErr_SetString(PyExc_OverflowError,
"byte string is too large");
return NULL;
}
/* Inline PyObject_NewVar */
op = (PyBytesObject *)PyObject_MALLOC(sizeof(PyBytesObject) + size);
op = (PyBytesObject *)PyObject_MALLOC(PyBytesObject_SIZE + size);
if (op == NULL)
return PyErr_NoMemory();
PyObject_INIT_VAR(op, &PyBytes_Type, size);
@ -117,7 +126,7 @@ PyBytes_FromString(const char *str)
assert(str != NULL);
size = strlen(str);
if (size > PY_SSIZE_T_MAX - sizeof(PyBytesObject)) {
if (size > PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
PyErr_SetString(PyExc_OverflowError,
"byte string is too long");
return NULL;
@ -138,7 +147,7 @@ PyBytes_FromString(const char *str)
}
/* Inline PyObject_NewVar */
op = (PyBytesObject *)PyObject_MALLOC(sizeof(PyBytesObject) + size);
op = (PyBytesObject *)PyObject_MALLOC(PyBytesObject_SIZE + size);
if (op == NULL)
return PyErr_NoMemory();
PyObject_INIT_VAR(op, &PyBytes_Type, size);
@ -746,13 +755,12 @@ string_repeat(register PyBytesObject *a, register Py_ssize_t n)
return (PyObject *)a;
}
nbytes = (size_t)size;
if (nbytes + sizeof(PyBytesObject) <= nbytes) {
if (nbytes + PyBytesObject_SIZE <= nbytes) {
PyErr_SetString(PyExc_OverflowError,
"repeated bytes are too long");
return NULL;
}
op = (PyBytesObject *)
PyObject_MALLOC(sizeof(PyBytesObject) + nbytes);
op = (PyBytesObject *)PyObject_MALLOC(PyBytesObject_SIZE + nbytes);
if (op == NULL)
return PyErr_NoMemory();
PyObject_INIT_VAR(op, &PyBytes_Type, size);
@ -2803,7 +2811,7 @@ static PyObject *
string_sizeof(PyBytesObject *v)
{
Py_ssize_t res;
res = sizeof(PyBytesObject) + Py_SIZE(v) * Py_TYPE(v)->tp_itemsize;
res = PyBytesObject_SIZE + Py_SIZE(v) * Py_TYPE(v)->tp_itemsize;
return PyLong_FromSsize_t(res);
}
@ -3080,7 +3088,7 @@ static PyObject *str_iter(PyObject *seq);
PyTypeObject PyBytes_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"bytes",
sizeof(PyBytesObject),
PyBytesObject_SIZE,
sizeof(char),
string_dealloc, /* tp_dealloc */
0, /* tp_print */
@ -3175,7 +3183,7 @@ _PyBytes_Resize(PyObject **pv, Py_ssize_t newsize)
_Py_DEC_REFTOTAL;
_Py_ForgetReference(v);
*pv = (PyObject *)
PyObject_REALLOC((char *)v, sizeof(PyBytesObject) + newsize);
PyObject_REALLOC((char *)v, PyBytesObject_SIZE + newsize);
if (*pv == NULL) {
PyObject_Del(v);
PyErr_NoMemory();