From 0376fdb483464ded73a5c1a8bba97b196af23b6d Mon Sep 17 00:00:00 2001
From: Andreas Stöckel <astoecke@techfak.uni-bielefeld.de>
Date: Fri, 6 Feb 2015 02:24:07 +0100
Subject: Continue writing parser for plain document format

---
 src/plugins/plain/DynamicTokenTree.cpp | 115 +++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 src/plugins/plain/DynamicTokenTree.cpp

(limited to 'src/plugins/plain/DynamicTokenTree.cpp')

diff --git a/src/plugins/plain/DynamicTokenTree.cpp b/src/plugins/plain/DynamicTokenTree.cpp
new file mode 100644
index 0000000..25f6a54
--- /dev/null
+++ b/src/plugins/plain/DynamicTokenTree.cpp
@@ -0,0 +1,115 @@
+/*
+    Ousía
+    Copyright (C) 2014  Benjamin Paaßen, Andreas Stöckel
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program 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 General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "DynamicTokenTree.hpp"
+
+namespace ousia {
+
+/* Class DynamicTokenTree::Node */
+
+DynamicTokenTree::Node::Node() : descriptor(nullptr) {}
+
+/* Class DynamicTokenTree */
+
+bool DynamicTokenTree::registerToken(const std::string &token,
+                                     const TokenDescriptor *descriptor) noexcept
+{
+	// Abort if the token is empty -- this would taint the root node
+	if (token.empty()) {
+		return false;
+	}
+
+	// Iterate over each character in the given string and insert them as
+	// (new) nodes
+	Node *node = &root;
+	for (size_t i = 0; i < token.size(); i++) {
+		// Insert a new node if this one does not exist
+		const char c = token[i];
+		auto it = node->children.find(c);
+		if (it == node->children.end()) {
+			it = node->children.emplace(c, std::unique_ptr<Node>(new Node{})).first;
+		}
+		node = it->second.get();
+	}
+
+	// If the resulting node already has a descriptor set, we're screwed.
+	if (node->descriptor != nullptr) {
+		return false;
+	}
+
+	// Otherwise just set the descriptor to the given descriptor.
+	node->descriptor = descriptor;
+	return true;
+}
+
+bool DynamicTokenTree::unregisterToken(const std::string &token) noexcept
+{
+	// We cannot remove empty tokens as we need to access the fist character
+	// upfront
+	if (token.empty()) {
+		return false;
+	}
+
+	// First pass -- search the node in the path that can be deleted
+	Node *subtreeRoot = &root;
+	char subtreeKey = token[0];
+	Node *node = &root;
+	for (size_t i = 0; i < token.size() - 1; i++) {
+		// Go to the next node, abort if the tree ends unexpectedly
+		auto it = node->children.find(token[i]);
+		if (it == node->children.end()) {
+			return false;
+		}
+
+		// Reset the subtree handler if this node has another descriptor
+		Node *child = it->second.get();
+		if ((child->descriptor != nullptr || child->children.size() > 1)) {
+			subtreeRoot = child;
+			subtreeKey = token[i + 1];
+		}
+		node = child;
+	}
+
+	// If the leaf node, we cannot delete the subtree. Set the
+	// descriptor to nullptr instead
+	if (!node->children.empty()) {
+		node->descriptor = nullptr;
+		return true;
+	}
+
+	// If we end up here, we can safely delete the complete subtree
+	subtreeRoot->children.erase(subtreeKey);
+	return true;
+}
+
+const TokenDescriptor *DynamicTokenTree::hasToken(
+    const std::string &token) const noexcept
+{
+	Node const *node = &root;
+	for (size_t i = 0; i < token.size(); i++) {
+		const char c = token[i];
+		auto it = node->children.find(c);
+		if (it == node->children.end()) {
+			return nullptr;
+		}
+		node = it->second.get();
+	}
+	return node->descriptor;
+}
+}
+
-- 
cgit v1.2.3