--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/source/fitz/tree.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,137 @@
+// Copyright (C) 2004-2021 Artifex Software, Inc.
+//
+// This file is part of MuPDF.
+//
+// MuPDF is free software: you can redistribute it and/or modify it under the
+// terms of the GNU Affero General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// MuPDF is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+// details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
+//
+// Alternative licensing terms are available from the licensor.
+// For commercial licensing, see <https://www.artifex.com/> or contact
+// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
+// CA 94129, USA, for further information.
+
+#include "mupdf/fitz.h"
+
+#include <string.h>
+
+/* AA-tree */
+
+struct fz_tree
+{
+	char *key;
+	void *value;
+	fz_tree *left, *right;
+	int level;
+};
+
+static fz_tree tree_sentinel = { "", NULL, &tree_sentinel, &tree_sentinel, 0 };
+
+static fz_tree *fz_tree_new_node(fz_context *ctx, const char *key, void *value)
+{
+	fz_tree *node = fz_malloc_struct(ctx, fz_tree);
+	fz_try(ctx)
+	{
+		node->key = fz_strdup(ctx, key);
+		node->value = value;
+		node->left = node->right = &tree_sentinel;
+		node->level = 1;
+	}
+	fz_catch(ctx)
+	{
+		fz_free(ctx, node);
+		fz_rethrow(ctx);
+	}
+	return node;
+}
+
+void *fz_tree_lookup(fz_context *ctx, fz_tree *node, const char *key)
+{
+	if (node)
+	{
+		while (node != &tree_sentinel)
+		{
+			int c = strcmp(key, node->key);
+			if (c == 0)
+				return node->value;
+			else if (c < 0)
+				node = node->left;
+			else
+				node = node->right;
+		}
+	}
+	return NULL;
+}
+
+static fz_tree *fz_tree_skew(fz_tree *node)
+{
+	if (node->level != 0)
+	{
+		if (node->left->level == node->level)
+		{
+			fz_tree *save = node;
+			node = node->left;
+			save->left = node->right;
+			node->right = save;
+		}
+		node->right = fz_tree_skew(node->right);
+	}
+	return node;
+}
+
+static fz_tree *fz_tree_split(fz_tree *node)
+{
+	if (node->level != 0 && node->right->right->level == node->level)
+	{
+		fz_tree *save = node;
+		node = node->right;
+		save->right = node->left;
+		node->left = save;
+		node->level++;
+		node->right = fz_tree_split(node->right);
+	}
+	return node;
+}
+
+fz_tree *fz_tree_insert(fz_context *ctx, fz_tree *node, const char *key, void *value)
+{
+	if (node && node != &tree_sentinel)
+	{
+		int c = strcmp(key, node->key);
+		if (c < 0)
+			node->left = fz_tree_insert(ctx, node->left, key, value);
+		else
+			node->right = fz_tree_insert(ctx, node->right, key, value);
+		node = fz_tree_skew(node);
+		node = fz_tree_split(node);
+		return node;
+	}
+	else
+	{
+		return fz_tree_new_node(ctx, key, value);
+	}
+}
+
+void fz_drop_tree(fz_context *ctx, fz_tree *node, void (*dropfunc)(fz_context *ctx, void *value))
+{
+	if (node)
+	{
+		if (node->left != &tree_sentinel)
+			fz_drop_tree(ctx, node->left, dropfunc);
+		if (node->right != &tree_sentinel)
+			fz_drop_tree(ctx, node->right, dropfunc);
+		fz_free(ctx, node->key);
+		if (dropfunc)
+			dropfunc(ctx, node->value);
+		fz_free(ctx, node);
+	}
+}