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/*
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 "TokenTrie.hpp"
namespace ousia {
/* Class DynamicTokenTree::Node */
TokenTrie::Node::Node() : type(Tokens::Empty) {}
/* Class DynamicTokenTree */
bool TokenTrie::registerToken(const std::string &token,
TokenId type) 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::make_shared<Node>()).first;
}
node = it->second.get();
}
// If the resulting node already has a type set, we're screwed.
if (node->type != Tokens::Empty) {
return false;
}
// Otherwise just set the type to the given type.
node->type = type;
return true;
}
bool TokenTrie::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(); 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 type
node = it->second.get();
if ((node->type != Tokens::Empty || node->children.size() > 1) &&
(i + 1 != token.size())) {
subtreeRoot = node;
subtreeKey = token[i + 1];
}
}
// If the node type is already Tokens::Empty, we cannot do anything here
if (node->type == Tokens::Empty) {
return false;
}
// If the target node has children, we cannot delete the subtree. Set the
// type to Tokens::Empty instead
if (!node->children.empty()) {
node->type = Tokens::Empty;
return true;
}
// If we end up here, we can safely delete the complete subtree
subtreeRoot->children.erase(subtreeKey);
return true;
}
TokenId TokenTrie::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 Tokens::Empty;
}
node = it->second.get();
}
return node->type;
}
}
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