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/* Parse tree node implementation */
#include "Python.h"
#include "node.h"
#include "errcode.h"
node *
PyNode_New(int type)
{
node *n = PyMem_NEW(node, 1);
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. */
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;
return result;
}
/* A gimmick to make massive numbers of reallocs quicker. The result is
* a number >= the input. For n=0 we must return 0.
* For n=1, we return 1, to avoid wasting memory in common 1-child nodes
* (XXX are those actually common?).
* Else for n <= 128, round up to the closest multiple of 4. Why 4?
* Rounding up to a multiple of an exact power of 2 is very efficient.
* Else 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).
* This would be straightforward if a node stored its current capacity. The
* code is tricky to avoid that.
*/
#define XXXROUNDUP(n) ((n) == 1 ? 1 : \
(n) <= 128 ? (((n) + 3) & ~3) : \
fancy_roundup(n))
int
PyNode_AddChild(register node *n1, int type, char *str, int lineno)
{
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 < required_capacity) {
n = n1->n_child;
PyMem_RESIZE(n, node, required_capacity);
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_nchildren = 0;
n->n_child = NULL;
return 0;
}
/* Forward */
static void freechildren(node *);
void
PyNode_Free(node *n)
{
if (n != NULL) {
freechildren(n);
PyMem_DEL(n);
}
}
static void
freechildren(node *n)
{
int i;
for (i = NCH(n); --i >= 0; )
freechildren(CHILD(n, i));
if (n->n_child != NULL)
PyMem_DEL(n->n_child);
if (STR(n) != NULL)
PyMem_DEL(STR(n));
}
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