139 lines
3.6 KiB
C
139 lines
3.6 KiB
C
/* 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 ? (((n) + 3) & ~3) : \
|
|
fancy_roundup(n))
|
|
|
|
|
|
int
|
|
PyNode_AddChild(register 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 (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 *);
|
|
|
|
|
|
void
|
|
PyNode_Free(node *n)
|
|
{
|
|
if (n != NULL) {
|
|
freechildren(n);
|
|
PyObject_FREE(n);
|
|
}
|
|
}
|
|
|
|
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));
|
|
}
|