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134 lines
3.6 KiB
134 lines
3.6 KiB
/* Parse tree node implementation */ |
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#include "Python.h" |
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#include "node.h" |
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#include "errcode.h" |
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node * |
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PyNode_New(int type) |
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{ |
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node *n = (node *) PyObject_MALLOC(1 * sizeof(node)); |
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if (n == NULL) |
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return NULL; |
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n->n_type = type; |
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n->n_str = NULL; |
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n->n_lineno = 0; |
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n->n_nchildren = 0; |
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n->n_child = NULL; |
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return n; |
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} |
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/* See comments at XXXROUNDUP below. Returns -1 on overflow. */ |
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static int |
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fancy_roundup(int n) |
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{ |
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/* Round up to the closest power of 2 >= n. */ |
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int result = 256; |
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assert(n > 128); |
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while (result < n) { |
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result <<= 1; |
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if (result <= 0) |
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return -1; |
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} |
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return result; |
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} |
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/* A gimmick to make massive numbers of reallocs quicker. The result is |
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* a number >= the input. In PyNode_AddChild, it's used like so, when |
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* we're about to add child number current_size + 1: |
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* |
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* if XXXROUNDUP(current_size) < XXXROUNDUP(current_size + 1): |
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* allocate space for XXXROUNDUP(current_size + 1) total children |
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* else: |
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* we already have enough space |
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* |
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* Since a node starts out empty, we must have |
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* |
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* XXXROUNDUP(0) < XXXROUNDUP(1) |
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* |
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* so that we allocate space for the first child. One-child nodes are very |
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* common (presumably that would change if we used a more abstract form |
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* of syntax tree), so to avoid wasting memory it's desirable that |
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* XXXROUNDUP(1) == 1. That in turn forces XXXROUNDUP(0) == 0. |
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* |
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* Else for 2 <= n <= 128, we round up to the closest multiple of 4. Why 4? |
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* Rounding up to a multiple of an exact power of 2 is very efficient, and |
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* most nodes with more than one child have <= 4 kids. |
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* |
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* Else we call fancy_roundup() to grow proportionately to n. We've got an |
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* extreme case then (like test_longexp.py), and on many platforms doing |
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* anything less than proportional growth leads to exorbitant runtime |
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* (e.g., MacPython), or extreme fragmentation of user address space (e.g., |
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* Win98). |
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* |
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* In a run of compileall across the 2.3a0 Lib directory, Andrew MacIntyre |
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* reported that, with this scheme, 89% of PyMem_RESIZE calls in |
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* PyNode_AddChild passed 1 for the size, and 9% passed 4. So this usually |
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* wastes very little memory, but is very effective at sidestepping |
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* platform-realloc disasters on vulnernable platforms. |
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* |
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* Note that this would be straightforward if a node stored its current |
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* capacity. The code is tricky to avoid that. |
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*/ |
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#define XXXROUNDUP(n) ((n) <= 1 ? (n) : \ |
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(n) <= 128 ? (((n) + 3) & ~3) : \ |
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fancy_roundup(n)) |
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int |
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PyNode_AddChild(register node *n1, int type, char *str, int lineno) |
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{ |
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const int nch = n1->n_nchildren; |
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int current_capacity; |
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int required_capacity; |
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node *n; |
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if (nch == INT_MAX || nch < 0) |
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return E_OVERFLOW; |
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current_capacity = XXXROUNDUP(nch); |
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required_capacity = XXXROUNDUP(nch + 1); |
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if (current_capacity < 0 || required_capacity < 0) |
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return E_OVERFLOW; |
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if (current_capacity < required_capacity) { |
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n = n1->n_child; |
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n = (node *) PyObject_REALLOC(n, |
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required_capacity * sizeof(node)); |
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if (n == NULL) |
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return E_NOMEM; |
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n1->n_child = n; |
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} |
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n = &n1->n_child[n1->n_nchildren++]; |
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n->n_type = type; |
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n->n_str = str; |
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n->n_lineno = lineno; |
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n->n_nchildren = 0; |
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n->n_child = NULL; |
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return 0; |
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} |
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/* Forward */ |
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static void freechildren(node *); |
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void |
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PyNode_Free(node *n) |
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{ |
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if (n != NULL) { |
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freechildren(n); |
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PyObject_FREE(n); |
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} |
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} |
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static void |
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freechildren(node *n) |
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{ |
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int i; |
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for (i = NCH(n); --i >= 0; ) |
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freechildren(CHILD(n, i)); |
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if (n->n_child != NULL) |
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PyObject_FREE(n->n_child); |
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if (STR(n) != NULL) |
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PyObject_FREE(STR(n)); |
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}
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