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improve performance of writing past the end of the file for cStringIO 

(http://bugs.python.org/issue10045)
This commit is contained in:
Fred Drake 2010-10-11 19:13:04 +00:00
parent 5e8349e5cc
commit 577acb4e30
3 changed files with 22 additions and 40 deletions
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1
Misc/ACKS
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@ -755,6 +755,7 @@ Peter Stoehr
Casper Stoel
Michael Stone
Ken Stox
Patrick Strawderman
Dan Stromberg
Daniel Stutzbach
Nathan Sullivan

3
Misc/NEWS
View File

@ -48,6 +48,9 @@ Core and Builtins
Library
-------
- Issue #10045: Improved performance when writing after seeking past the
end of the "file" in cStringIO.
- Issue #9948: Fixed problem of losing filename case information.
- Issue #9437: Fix building C extensions with non-default LDFLAGS.

58
Modules/cStringIO.c
View File

@ -339,12 +339,12 @@ IO_iternext(Iobject *self)
/* Read-write object methods */
PyDoc_STRVAR(O_seek__doc__,
PyDoc_STRVAR(IO_seek__doc__,
"seek(position) -- set the current position\n"
"seek(position, mode) -- mode 0: absolute; 1: relative; 2: relative to EOF");
static PyObject *
O_seek(Oobject *self, PyObject *args) {
IO_seek(Iobject *self, PyObject *args) {
Py_ssize_t position;
int mode = 0;
@ -359,25 +359,10 @@ O_seek(Oobject *self, PyObject *args) {
position += self->pos;
}
if (position > self->buf_size) {
char *newbuf;
self->buf_size*=2;
if (self->buf_size <= position) self->buf_size=position+1;
newbuf = (char*) realloc(self->buf,self->buf_size);
if (!newbuf) {
free(self->buf);
self->buf = 0;
self->buf_size=self->pos=0;
return PyErr_NoMemory();
}
self->buf = newbuf;
}
else if (position < 0) position=0;
if (position < 0) position=0;
self->pos=position;
while (--position >= self->string_size) self->buf[position]=0;
Py_INCREF(Py_None);
return Py_None;
}
@ -414,6 +399,19 @@ O_cwrite(PyObject *self, const char *c, Py_ssize_t l) {
oself->buf = newbuf;
}
if (oself->string_size < oself->pos) {
/* In case of overseek, pad with null bytes the buffer region between
the end of stream and the current position.
0 lo string_size hi
| |<---used--->|<----------available----------->|
| | <--to pad-->|<---to write---> |
0 buf position
*/
memset(oself->buf + oself->string_size, '\0',
(oself->pos - oself->string_size) * sizeof(char));
}
memcpy(oself->buf+oself->pos,c,l);
assert(oself->pos + l < INT_MAX);
@ -497,12 +495,12 @@ static struct PyMethodDef O_methods[] = {
{"readline", (PyCFunction)IO_readline, METH_VARARGS, IO_readline__doc__},
{"readlines", (PyCFunction)IO_readlines,METH_VARARGS, IO_readlines__doc__},
{"reset", (PyCFunction)IO_reset, METH_NOARGS, IO_reset__doc__},
{"seek", (PyCFunction)IO_seek, METH_VARARGS, IO_seek__doc__},
{"tell", (PyCFunction)IO_tell, METH_NOARGS, IO_tell__doc__},
{"truncate", (PyCFunction)IO_truncate, METH_VARARGS, IO_truncate__doc__},
/* Read-write StringIO specific methods: */
{"close", (PyCFunction)O_close, METH_NOARGS, O_close__doc__},
{"seek", (PyCFunction)O_seek, METH_VARARGS, O_seek__doc__},
{"write", (PyCFunction)O_write, METH_VARARGS, O_write__doc__},
{"writelines", (PyCFunction)O_writelines, METH_O, O_writelines__doc__},
{NULL, NULL} /* sentinel */
@ -595,26 +593,6 @@ I_close(Iobject *self, PyObject *unused) {
return Py_None;
}
static PyObject *
I_seek(Iobject *self, PyObject *args) {
Py_ssize_t position;
int mode = 0;
if (!IO__opencheck(IOOOBJECT(self))) return NULL;
if (!PyArg_ParseTuple(args, "n|i:seek", &position, &mode))
return NULL;
if (mode == 2) position += self->string_size;
else if (mode == 1) position += self->pos;
if (position < 0) position=0;
self->pos=position;
Py_INCREF(Py_None);
return Py_None;
}
static struct PyMethodDef I_methods[] = {
/* Common methods: */
{"flush", (PyCFunction)IO_flush, METH_NOARGS, IO_flush__doc__},
@ -624,12 +602,12 @@ static struct PyMethodDef I_methods[] = {
{"readline", (PyCFunction)IO_readline, METH_VARARGS, IO_readline__doc__},
{"readlines", (PyCFunction)IO_readlines,METH_VARARGS, IO_readlines__doc__},
{"reset", (PyCFunction)IO_reset, METH_NOARGS, IO_reset__doc__},
{"seek", (PyCFunction)IO_seek, METH_VARARGS, IO_seek__doc__},
{"tell", (PyCFunction)IO_tell, METH_NOARGS, IO_tell__doc__},
{"truncate", (PyCFunction)IO_truncate, METH_VARARGS, IO_truncate__doc__},
/* Read-only StringIO specific methods: */
{"close", (PyCFunction)I_close, METH_NOARGS, O_close__doc__},
{"seek", (PyCFunction)I_seek, METH_VARARGS, O_seek__doc__},
{NULL, NULL}
};