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#include <stddef.h>
#include "allocator_internal.h"
TreeAlloc *insert_node_at(void *address, uintptr_t padding, uintptr_t align, uintptr_t size) {
return NULL;
}
/*
* Search for the node whose allocated region contains an address.
*/
TreeAlloc *search_by_address(TreeAlloc *root, void *address) {
TreeAlloc *head = root;
while (1) {
if (head > (TreeAlloc*) address) {
if (head->left == NULL) {
return NULL;
} else {
head = head->left;
}
} else {
if (head->right == NULL || head->right > (TreeAlloc*) address) {
return head;
} else {
head = head->right;
}
}
}
}
static uintptr_t effective_size(TreeAlloc *head, uintptr_t padding, uintptr_t align) {
return head->size - (align_after(head + padding, align) - (void*) head);
}
/*
* This is the most optimistic estimate of size that we can use which also preserves the ordering over
* the tree. I had planned to use effective_size before I realized that it would break the tree
* ordering.
*/
static uintptr_t pessimistic_size(TreeAlloc *head, uintptr_t padding, uintptr_t align) {
return head->size - padding - align + 1;
}
TreeAlloc *search_by_size(TreeAlloc *root, uintptr_t padding, uintptr_t align, uintptr_t size) {
TreeAlloc *head = root;
while (1) {
uintptr_t esize = pessimistic_size(head, padding, align);
if (esize < size) {
if (head->right == NULL) {
return NULL;
} else {
head = head->right;
}
} else {
if (head->left == NULL || pessimistic_size(head->left, padding, align) < size) {
return head;
} else {
head = head->left;
}
}
}
}
TreeAlloc *get_sibling(TreeAlloc *ta) {
TreeAlloc *p = ta->parent;
if (!p)
return NULL;
else if (p->left == ta)
return p->right;
else
return p->left;
}
void rotate_left(TreeAlloc *ta) {
TreeAlloc *parent, *tmp;
parent = ta->parent;
tmp = ta->right;
if (!tmp) return;
ta->right = tmp->left;
tmp->left = ta;
ta->parent = tmp;
if (ta->right) ta->right->parent = ta;
if (parent) {
if (ta == parent->left)
parent->left = tmp;
else
parent->right = tmp;
}
tmp->parent = parent;
}
void rotate_right(TreeAlloc *ta) {
TreeAlloc *parent, *tmp;
parent = ta->parent;
tmp = ta->left;
if (!tmp) return;
ta->left = tmp->right;
tmp->right = ta;
ta->parent = tmp;
if (ta->left) ta->left->parent = ta;
if (parent) {
if (ta == parent->left)
parent->left = tmp;
else
parent->right = tmp;
}
tmp->parent = parent;
}
void repair_tree_after_insert(TreeAlloc *ta) {
TreeAlloc *parent = ta->parent;
if (parent == NULL) {
ta->color = COLOR_BLACK;
return;
}
TreeAlloc *grandparent = parent->parent;
TreeAlloc *uncle = get_sibling(parent);
if (parent->color == COLOR_RED) {
if (uncle != NULL && uncle->color == COLOR_RED) {
parent->color = COLOR_BLACK;
uncle->color = COLOR_BLACK;
grandparent = COLOR_RED;
repair_tree(grandparent);
} else {
if (ta == parent->left && parent == grandparent->left) {
rotate_left(parent);
ta = ta->left;
} else {
rotate_right(parent);
ta = ta->right;
}
parent = ta->parent;
grandparent = parent->parent;
if (ta == parent->left) {
rotate_right(grandparent);
} else {
rotate_left(grandparent);
}
parent->color = COLOR_BLACK;
grandparent->color = COLOR_RED;
}
}
}
// TODO: Rewrite for self-balancing tree.
void remove_node(TreeAlloc** root_ptr, TreeAlloc* node) {
TreeAlloc *replace = NULL;
if (node->left == NULL) {
replace = node->right;
} else if (node->right != NULL) {
replace = node->right;
TreeAlloc *head = node->left;
while (head->right != NULL) {
head = head->right;
}
head->right = head->parent->right;
head->right->parent = head;
}
if (node->parent == NULL) {
replace->parent = NULL;
*root_ptr = replace;
} else {
if (node == node->parent->left) {
node->parent->left = replace;
} else {
node->parent->right = replace;
}
}
}
// Inserts a node into an empty tree.
void insert_singleton(TreeAlloc **root_ptr, TreeAlloc *to_insert) {
*root_ptr = to_insert;
to_insert->parent = NULL;
repair_tree_after_insert(to_insert);
}
void insert_right(TreeAlloc** root_ptr, TreeAlloc* to_insert, TreeAlloc* after) {
if (after->right != NULL) {
after->right->parent = to_insert;
to_insert->right = after->right;
}
after->right = to_insert;
to_insert->parent = after;
repair_tree_after_insert(to_insert);
}
void insert_left(TreeAlloc** root_ptr, TreeAlloc* to_insert, TreeAlloc* before) {
if (before->left != NULL) {
before->left->parent = to_insert;
to_insert->left = before->left;
}
before->left = to_insert;
to_insert->parent = before;
repair_tree_after_insert(to_insert);
}
void unalloc(Arena *arena, void *addr) {
if (arena->root_treealloc == NULL) {
arena->error("attempt to unallocate when there are no allocations!");
return;
}
// Find the node this address belongs to
TreeAlloc *node = search_by_address(arena->root_treealloc, addr);
if (node == NULL) {
arena->error("attempt to free memory outside any allocations!");
return;
}
// Handle the watermark allocator in this region
if (node->type == RT_WATERMARK) {
// TODO: handle watermark deallocation
return;
}
// Get rid of it
remove_node(&arena->root_treealloc, node);
// If there's free space on either side of it, merge it with the free space into a bigger chunk of
// free space.
uintptr_t size = node->size;
FreeSpace *start = (FreeSpace*) node;
if (node->before != NULL && node->before->type == RT_FREESPACE) {
start = (FreeSpace*) node->before;
size += node->before->size;
remove_node((TreeAlloc**) &arena->root_freespace, node->before);
}
if (node->after != NULL && node->after->type == RT_FREESPACE) {
size += node->after->size;
remove_node((TreeAlloc**) &arena->root_freespace, node->after);
}
start->type = RT_FREESPACE;
start->size = size;
// And finally, insert the resulting free space.
if (arena->root_freespace == NULL) {
insert_singleton((TreeAlloc**) &arena->root_freespace, (TreeAlloc*) start);
} else {
TreeAlloc *insert_point = search_by_size((TreeAlloc*) arena->root_freespace, 0, 1, size);
if (insert_point == NULL) {
TreeAlloc *head = (TreeAlloc*) arena->root_freespace;
while (head->right != NULL) {
head = head->right;
}
insert_right((TreeAlloc**) &arena->root_freespace, (TreeAlloc*) start, head);
} else {
insert_left((TreeAlloc**) &arena->root_freespace, (TreeAlloc*) start, insert_point);
}
}
// TODO
}
void *alloc(Arena arena, uintptr_t size, uintptr_t align) {
// TODO
return NULL;
}
void *alloc_growable(Arena arena, uintptr_t size, uintptr_t align) {
// TODO
return NULL;
}