/* 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)); | |
} |