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bpo-47005: Improve performance of bytearray_repeat and bytearray_irepeat #31856

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Merged
sweeneyde merged 3 commits into from
Mar 17, 2022
Merged

bpo-47005: Improve performance of bytearray_repeat and bytearray_irepeat #31856

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9e5b720
improve performance of bytearray_repeat and bytearray_irepeat
eendebakpt Mar 13, 2022
42bbf49
use Py_MIN; add comment
eendebakpt Mar 13, 2022
a28f791
📜🤖 Added by blurb_it.
blurb-it[bot] Mar 13, 2022
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-03-13-21-04-20.bpo-47005.OHBfCc.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Improve performance of ``bytearray_repeat`` and ``bytearray_irepeat`` by reducing the number of invocations of ``memcpy``.
28 changes: 22 additions & 6 deletions Objects/bytearrayobject.c
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Expand Up @@ -335,9 +335,19 @@ bytearray_repeat(PyByteArrayObject *self, Py_ssize_t count)
if (mysize == 1)
memset(result->ob_bytes, buf[0], size);
else {
Py_ssize_t i;
for (i = 0; i < count; i++)
memcpy(result->ob_bytes + i*mysize, buf, mysize);
Py_ssize_t i, j;

i = 0;
if (i < size) {
memcpy(result->ob_bytes, buf, mysize);
i = mysize;
}
// repeatedly double the number of bytes copied
while (i < size) {
j = Py_MIN(i, size - i);
memcpy(result->ob_bytes + i, result->ob_bytes, j);
i += j;
}
}
}
return (PyObject *)result;
Expand All @@ -363,9 +373,15 @@ bytearray_irepeat(PyByteArrayObject *self, Py_ssize_t count)
if (mysize == 1)
memset(buf, buf[0], size);
else {
Py_ssize_t i;
for (i = 1; i < count; i++)
memcpy(buf + i*mysize, buf, mysize);
Py_ssize_t i, j;

i = mysize;
// repeatedly double the number of bytes copied
while (i < size) {
j = Py_MIN(i, size - i);
memcpy(buf + i, buf, j);
i += j;
}
}

Py_INCREF(self);
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