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GvR's idea to use memset() for the most common special case of repeating

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a single character.  Shaves another 10% off the running time by avoiding
the lg2(N) loops and cache effects for the other cases.
This commit is contained in:
Raymond Hettinger 2003-01-06 22:42:41 +00:00
parent 2720b0dff8
commit 0a2f849b79
1 changed files with 5 additions and 1 deletions
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6
Objects/stringobject.c
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@ -966,6 +966,11 @@ string_repeat(register PyStringObject *a, register int n)
PyObject_INIT_VAR(op, &PyString_Type, size); PyObject_INIT_VAR(op, &PyString_Type, size);
op->ob_shash = -1; op->ob_shash = -1;
op->ob_sstate = SSTATE_NOT_INTERNED; op->ob_sstate = SSTATE_NOT_INTERNED;
op->ob_sval[size] = '\0';
if (a->ob_size == 1 && n > 0) {
memset(op->ob_sval, a->ob_sval[0] , n);
return (PyObject *) op;
}
i = 0; i = 0;
if (i < size) { if (i < size) {
memcpy(op->ob_sval, a->ob_sval, (int) a->ob_size); memcpy(op->ob_sval, a->ob_sval, (int) a->ob_size);
@ -976,7 +981,6 @@ string_repeat(register PyStringObject *a, register int n)
memcpy(op->ob_sval+i, op->ob_sval, j); memcpy(op->ob_sval+i, op->ob_sval, j);
i += j; i += j;
} }
op->ob_sval[size] = '\0';
return (PyObject *) op; return (PyObject *) op;
} }