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cpython/Parser/node.c at 3.5 · python/cpython · GitHub
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node.c
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node.c
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/* Parse tree node implementation */
#include
"Python.h"
#include
"node.h"
#include
"errcode.h"
node
*
PyNode_New
(
int
type
)
{
node
*
n
=
(
node
*
)
PyObject_MALLOC
(
1
*
sizeof
(
node
));
if
(
n
==
NULL
)
return
NULL
;
n
->
n_type
=
type
;
n
->
n_str
=
NULL
;
n
->
n_lineno
=
0
;
n
->
n_nchildren
=
0
;
n
->
n_child
=
NULL
;
return
n
;
}
/* See comments at XXXROUNDUP below. Returns -1 on overflow. */
static
int
fancy_roundup
(
int
n
)
{
/* Round up to the closest power of 2 >= n. */
int
result
=
256
;
assert
(
n
>
128
);
while
(
result
<
n
) {
result
<<=
1
;
if
(
result
<=
0
)
return
-1
;
}
return
result
;
}
/* A gimmick to make massive numbers of reallocs quicker. The result is
* a number >= the input. In PyNode_AddChild, it's used like so, when
* we're about to add child number current_size + 1:
*
* if XXXROUNDUP(current_size) < XXXROUNDUP(current_size + 1):
* allocate space for XXXROUNDUP(current_size + 1) total children
* else:
* we already have enough space
*
* Since a node starts out empty, we must have
*
* XXXROUNDUP(0) < XXXROUNDUP(1)
*
* so that we allocate space for the first child. One-child nodes are very
* common (presumably that would change if we used a more abstract form
* of syntax tree), so to avoid wasting memory it's desirable that
* XXXROUNDUP(1) == 1. That in turn forces XXXROUNDUP(0) == 0.
*
* Else for 2 <= n <= 128, we round up to the closest multiple of 4. Why 4?
* Rounding up to a multiple of an exact power of 2 is very efficient, and
* most nodes with more than one child have <= 4 kids.
*
* Else we call fancy_roundup() to grow proportionately to n. We've got an
* extreme case then (like test_longexp.py), and on many platforms doing
* anything less than proportional growth leads to exorbitant runtime
* (e.g., MacPython), or extreme fragmentation of user address space (e.g.,
* Win98).
*
* In a run of compileall across the 2.3a0 Lib directory, Andrew MacIntyre
* reported that, with this scheme, 89% of PyObject_REALLOC calls in
* PyNode_AddChild passed 1 for the size, and 9% passed 4. So this usually
* wastes very little memory, but is very effective at sidestepping
* platform-realloc disasters on vulnerable platforms.
*
* Note that this would be straightforward if a node stored its current
* capacity. The code is tricky to avoid that.
*/
#define
XXXROUNDUP
(
n
) ((n) <= 1 ? (n) : \
(n) <= 128 ? (int)_Py_SIZE_ROUND_UP((n), 4) : \
fancy_roundup(n))
int
PyNode_AddChild
(
node
*
n1
,
int
type
,
char
*
str
,
int
lineno
,
int
col_offset
)
{
const
int
nch
=
n1
->
n_nchildren
;
int
current_capacity
;
int
required_capacity
;
node
*
n
;
if
(
nch
==
INT_MAX
||
nch
<
0
)
return
E_OVERFLOW
;
current_capacity
=
XXXROUNDUP
(
nch
);
required_capacity
=
XXXROUNDUP
(
nch
+
1
);
if
(
current_capacity
<
0
||
required_capacity
<
0
)
return
E_OVERFLOW
;
if
(
current_capacity
<
required_capacity
) {
if
((
size_t
)
required_capacity
>
PY_SIZE_MAX
/
sizeof
(
node
)) {
return
E_NOMEM
;
}
n
=
n1
->
n_child
;
n
=
(
node
*
)
PyObject_REALLOC
(
n
,
required_capacity
*
sizeof
(
node
));
if
(
n
==
NULL
)
return
E_NOMEM
;
n1
->
n_child
=
n
;
}
n
=
&
n1
->
n_child
[
n1
->
n_nchildren
++
];
n
->
n_type
=
type
;
n
->
n_str
=
str
;
n
->
n_lineno
=
lineno
;
n
->
n_col_offset
=
col_offset
;
n
->
n_nchildren
=
0
;
n
->
n_child
=
NULL
;
return
0
;
}
/* Forward */
static
void
freechildren
(
node
*
);
static
Py_ssize_t
sizeofchildren
(
node
*
n
);
void
PyNode_Free
(
node
*
n
)
{
if
(
n
!=
NULL
) {
freechildren
(
n
);
PyObject_FREE
(
n
);
}
}
Py_ssize_t
_PyNode_SizeOf
(
node
*
n
)
{
Py_ssize_t
res
=
0
;
if
(
n
!=
NULL
)
res
=
sizeof
(
node
)
+
sizeofchildren
(
n
);
return
res
;
}
static
void
freechildren
(
node
*
n
)
{
int
i
;
for
(
i
=
NCH
(
n
);
--
i
>=
0
; )
freechildren
(
CHILD
(
n
,
i
));
if
(
n
->
n_child
!=
NULL
)
PyObject_FREE
(
n
->
n_child
);
if
(
STR
(
n
)
!=
NULL
)
PyObject_FREE
(
STR
(
n
));
}
static
Py_ssize_t
sizeofchildren
(
node
*
n
)
{
Py_ssize_t
res
=
0
;
int
i
;
for
(
i
=
NCH
(
n
);
--
i
>=
0
; )
res
+=
sizeofchildren
(
CHILD
(
n
,
i
));
if
(
n
->
n_child
!=
NULL
)
/* allocated size of n->n_child array */
res
+=
XXXROUNDUP
(
NCH
(
n
))
*
sizeof
(
node
);
if
(
STR
(
n
)
!=
NULL
)
res
+=
strlen
(
STR
(
n
))
+
1
;
return
res
;
}
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