diff --git a/util/test_tree.c b/util/test_tree.c
new file mode 100644
index 0000000..1633d6f
--- /dev/null
+++ b/util/test_tree.c
@@ -0,0 +1,80 @@
+//$CC -g test_tree.c tree.c ../driver/random/random.c
+
+#include "stdlib.h"
+#include "stdio.h"
+
+#include "tree.h"
+
+
+tree_Tree *tree;
+
+void insert(int a) {
+	bool new;
+	int *d = tree_Insert(tree, a, &new);
+	if (new)
+		*d = 1;
+	else
+		(*d)++;
+}
+
+int count(int a) {
+	int *d = tree_Find(tree, a);
+	if (!d)
+		return 0;
+	else
+		return *d;
+}
+
+void delete (int a) {
+	tree_Node *node = tree_FindNode(tree, a);
+	if (!node)
+		return;
+
+	(*(int *)node->data)--;
+	if ((*(int *)node->data) == 0)
+		tree_Delete(tree, node);
+}
+
+
+int main() {
+	tree = tree_Create(sizeof(int));
+
+	insert(1);
+	insert(2);
+	insert(3);
+	insert(6);
+	insert(1);
+
+	printf("%d\n", count(2));
+	printf("%d\n", count(4));
+	printf("%d\n", count(1));
+	delete (1);
+	printf("%d\n", count(1));
+	delete (1);
+	printf("%d\n", count(1));
+	delete (1);
+	printf("%d\n", count(1));
+	delete (2);
+	printf("%d\n", count(1));
+
+	insert(7);
+	insert(10);
+	insert(54);
+	insert(18);
+	insert(63);
+	insert(39);
+
+	tree_Node *i = tree_FirstNode(tree);
+	while (i) {
+		printf(" %d", (int)i->key);
+		i = tree_Node_Next(i);
+	}
+	printf("\n");
+
+	i = tree_LastNode(tree);
+	while (i) {
+		printf(" %d", (int)i->key);
+		i = tree_Node_Previous(i);
+	}
+	printf("\n");
+}
diff --git a/util/tree.c b/util/tree.c
new file mode 100644
index 0000000..5d4db32
--- /dev/null
+++ b/util/tree.c
@@ -0,0 +1,164 @@
+
+#include "tree.h"
+#include "tree_internal.h"
+
+#include "../main.h"
+#include "../memory/memory.h"
+#include "../driver/random/random.h"
+#include "string.h"
+
+
+// Create allocates and creates a new default Tree object.
+tree_Tree *tree_Create(uintptr_t objectSize) {
+	tree_Tree *t  = kMalloc(sizeof(tree_Tree));
+	t->objectSize = objectSize;
+	t->size       = 0;
+	t->root       = 0;
+	return t;
+}
+
+
+static inline tree_Node *__tree_NewNode(tree_Tree *t, uintptr_t key, tree_Node *father, uintptr_t internal) {
+	t->size++;
+
+	tree_Node *node = kMalloc(sizeof(tree_Node) - 1 + t->objectSize);
+	node->left = node->right = 0;
+	node->father             = father;
+	node->key                = key;
+	node->internal           = internal;
+	return node;
+}
+
+static void __tree_DestroyNodes(tree_Node *node) {
+	if (node->left)
+		__tree_DestroyNodes(node->left);
+	if (node->right)
+		__tree_DestroyNodes(node->right);
+	kFree(node);
+}
+
+void tree_Destroy(tree_Tree *tree) {
+	if (tree->root)
+		__tree_DestroyNodes(tree->root);
+	kFree(tree);
+}
+
+
+// Will not return NULL
+// SysV ABI because of the 6 arguments
+SYSV_ABI static tree_Node *__tree_InsertNodes(tree_Tree *t, tree_Node *node, tree_Node *father, uintptr_t key, tree_Node **result, bool *added) {
+	if (!node) {
+		if (added)
+			*added = true;
+		return *result = __tree_NewNode(t, key, father, random_Rand() ^ key);
+	} else if (key < node->key) {
+		node->left = __tree_InsertNodes(t, node->left, node, key, result, added);
+		return node;
+	} else if (key > node->key) {
+		node->right = __tree_InsertNodes(t, node->right, node, key, result, added);
+		return node;
+	} else {
+		if (added)
+			*added = false;
+		*result = node;
+		return node;
+	}
+}
+
+tree_Node *tree_InsertNode(tree_Tree *t, uintptr_t key, bool *added) {
+	tree_Node *result;
+	t->root = __tree_InsertNodes(t, t->root, 0, key, &result, added);
+
+	if (*added)
+		__tree_treap_Adjust(result, &t->root);
+
+	return result;
+}
+
+void *tree_Insert(tree_Tree *t, uintptr_t key, bool *added) {
+	return tree_InsertNode(t, key, added)->data;
+}
+
+
+static tree_Node *__tree_FindNode(tree_Node *node, uintptr_t key) {
+	if (!node)
+		return NULL;
+	else if (key < node->key)
+		return __tree_FindNode(node->left, key);
+	else if (key > node->key)
+		return __tree_FindNode(node->right, key);
+	else
+		return node;
+}
+
+tree_Node *tree_FindNode(tree_Tree *t, uintptr_t key) {
+	return __tree_FindNode(t->root, key);
+}
+
+void *tree_Find(tree_Tree *t, uintptr_t key) {
+	tree_Node *node = tree_FindNode(t, key);
+	if (!node)
+		return NULL;
+	else
+		return node->data;
+}
+
+
+void tree_Delete(tree_Tree *t, tree_Node *node) {
+	while (node->left && node->right)
+		if (node->left->internal < node->right->internal)
+			__tree_Rotate(node->left, &t->root);
+		else
+			__tree_Rotate(node->right, &t->root);
+
+	if (node == t->root)
+		t->root = (node->left ? node->left : node->right);
+	__tree_Connect(node->father, (node->left ? node->left : node->right), __tree_Tell(node));
+
+	kFree(node);
+}
+
+
+tree_Node *tree_FirstNode(tree_Tree *tree) {
+	tree_Node *result = tree->root;
+	while (result->left)
+		result = result->left;
+	return result;
+}
+
+tree_Node *tree_LastNode(tree_Tree *tree) {
+	tree_Node *result = tree->root;
+	while (result->right)
+		result = result->right;
+	return result;
+}
+
+
+tree_Node *tree_Node_Next(tree_Node *node) {
+	if (node->right) {
+		tree_Node *result = node->right;
+		while (result->left)
+			result = result->left;
+		return result;
+	} else {
+		tree_Node *result = node;
+		while (result->father && __tree_Tell(result) == __tree_Right)
+			result = result->father;
+		return result->father;
+	}
+}
+
+// Node_Previous returns the previous node. Returns NULL if first.
+tree_Node *tree_Node_Previous(tree_Node *node) {
+	if (node->left) {
+		tree_Node *result = node->left;
+		while (result->right)
+			result = result->right;
+		return result;
+	} else {
+		tree_Node *result = node;
+		while (result->father && __tree_Tell(result) == __tree_Left)
+			result = result->father;
+		return result->father;
+	}
+}
diff --git a/util/tree.h b/util/tree.h
new file mode 100644
index 0000000..b8679f7
--- /dev/null
+++ b/util/tree.h
@@ -0,0 +1,75 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+typedef struct __tree_Node {
+	uintptr_t           key;          // node key
+	struct __tree_Node *left, *right; // left and right sons
+	struct __tree_Node *father;       // father node
+	uintptr_t           internal;     // internal data for balanced trees
+	char                data[1];      // placeholder for object data
+} tree_Node;
+
+// Tree is a basic tree-based associative container.
+//
+// Right now it's a Treap.
+typedef struct {
+	uintptr_t  objectSize; // size in bytes of the object
+	tree_Node *root;       // root of the tree, NULL if empty
+	uintptr_t  size;       // number of objects in the tree
+} tree_Tree;
+
+// Create allocates and creates a new default Tree object.
+tree_Tree *tree_Create(uintptr_t objectSize);
+
+// Destroy properly frees all data related to the structure, and itself.
+void tree_Destroy(tree_Tree *tree);
+
+// Insert inserts a new object (or locates an existing one).
+//
+// If *added is not NULL, it is set to true if the key does
+// not exist and is actually added.
+//
+// Newly allocated data is not zeroed, nor initialized in any way.
+//
+// Returns the pointer to the newly allocated (or existing) data.
+void *tree_Insert(tree_Tree *tree, uintptr_t key, bool *added);
+
+// InsertNode does the same as Insert, but returns Node* instead of data.
+tree_Node *tree_InsertNode(tree_Tree *tree, uintptr_t key, bool *added);
+
+// Find locates an existing object by its key.
+//
+// Returns NULL if the object does not exist.
+void *tree_Find(tree_Tree *tree, uintptr_t key);
+
+// FindNode returns an existing tree node by its key.
+//
+// Used for iterating the tree objects.
+tree_Node *tree_FindNode(tree_Tree *tree, uintptr_t key);
+
+// FirstNode returns the first node in increasing order.
+tree_Node *tree_FirstNode(tree_Tree *tree);
+
+// LastNode returns the last node in increasing order.
+tree_Node *tree_LastNode(tree_Tree *tree);
+
+// Delete deletes an existing node from the tree.
+void tree_Delete(tree_Tree *tree, tree_Node *node);
+
+// Node_Next returns the next node. Returns NULL if the node is the last.
+tree_Node *tree_Node_Next(tree_Node *node);
+
+// Node_Previous returns the previous node. Returns NULL if first.
+tree_Node *tree_Node_Previous(tree_Node *node);
+
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/util/tree_internal.h b/util/tree_internal.h
new file mode 100644
index 0000000..207cd35
--- /dev/null
+++ b/util/tree_internal.h
@@ -0,0 +1,60 @@
+#pragma once
+
+#include "tree.h"
+
+
+typedef enum {
+	__tree_Left,
+	__tree_Right,
+} __tree_ConnectType;
+
+static inline __tree_ConnectType __tree_ConnectType_Invert(__tree_ConnectType type) {
+	return (__tree_ConnectType)(!type);
+}
+
+static inline __tree_ConnectType __tree_Tell(tree_Node *son) {
+	if (!son->father)
+		return __tree_Left;
+	if (son->father->left == son)
+		return __tree_Left;
+	else
+		return __tree_Right;
+}
+
+static inline tree_Node *__tree_Get(tree_Node *father, __tree_ConnectType type) {
+	return (type == __tree_Left) ? father->left : father->right;
+}
+
+static inline void __tree_Connect(tree_Node *father, tree_Node *son, __tree_ConnectType type) {
+	if (son)
+		son->father = father;
+	if (father) {
+		if (type == __tree_Left)
+			father->left = son;
+		else
+			father->right = son;
+	}
+}
+
+// Rotates the node up.
+static inline void __tree_Rotate(tree_Node *node, tree_Node **root) {
+	if (!node->father)
+		return;
+
+	__tree_ConnectType type = __tree_Tell(node);
+
+	tree_Node *f = node->father,
+			  *b = __tree_Get(node, __tree_ConnectType_Invert(type));
+	__tree_Connect(f->father, node, __tree_Tell(f));
+	__tree_Connect(node, f, __tree_ConnectType_Invert(type));
+	__tree_Connect(f, b, type);
+
+	if (!node->father)
+		*root = node;
+}
+
+// Adjust the tree as a Treap
+static inline void __tree_treap_Adjust(tree_Node *node, tree_Node **root) {
+	while (node->father && node->father->internal > node->internal)
+		__tree_Rotate(node, root);
+}