Added some tree functions

Makefile

@@ -1,4 +1,4 @@
-objs = main.o tree_alloc.o
+objs = main.o tree_alloc.o util.o
 
 CC = clang
 COMMON_FLAGS = -std=c11

allocator_internal.h

@@ -41,9 +41,9 @@ typedef struct WatermarkAlloc {
   void *next_alloc;
 } WatermarkAlloc;
 
-void* align_after(void* address, int align);
-TreeAlloc *insert_node_at(void *address, int padding, int align, int size);
+void* align_after(void* address, uintptr_t align);
+TreeAlloc *insert_node_at(void *address, uintptr_t padding, uintptr_t align, uintptr_t size);
 TreeAlloc *search_by_address(TreeAlloc *root, void *address);
-TreeAlloc *search_by_size(TreeAlloc *root, int padding, int align, int size);
+TreeAlloc *search_by_size(TreeAlloc *root, uintptr_t padding, uintptr_t align, uintptr_t size);
 
 #endif

tree_alloc.c

@@ -3,42 +3,57 @@
 
 #include "allocator_internal.h"
 
-TreeAlloc *insert_node_at(void *address, int padding, int align, int size) {
+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) {
-	while (1) {
-		if (root < address) {
-			if (root->left)
-				root = root->left;
-			else
-				return root;
-		} else if (root > address) {
-			if (root->right)
-				root = root->right;
-			else
-				return root;
-		} else {
-			return root;
-		}
-	}
+  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;
+      }
+    }
+  }
 }
 
-TreeAlloc *search_by_size(TreeAlloc *root, int padding, int align, int size) {
-	while (1) {
-		if (root->size < size) {
-			if (root->left)
-				root = root->left;
-			else
-				return root;
-		} else if (root->size > address) {
-			if (root->right)
-				root = root->right;
-			else
-				return root;
-		} else {
-			return root;
-		}
-	}
+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;
+      }
+    }
+  }
 }

util.c

@@ -4,7 +4,7 @@
 void* align_after(void* address, int align) {
   uintptr_t addr = (uintptr_t) address;
   uintptr_t offset = addr % align;
-  if offset == 0 {
+  if (offset == 0) {
     return address;
   } else {
     return (void*) (addr + align - align % offset);