51becbde
 Peter M. Groen
Committed the ent...
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/* Copyright (C) 2019
*
* This file is part of the osdev components suite
*
* 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 2, 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include "mqttutil.h"
// boost
#include <boost/algorithm/string/split.hpp>
#include <boost/regex.hpp>
namespace osdev {
namespace components {
namespace mqtt {
bool isValidTopic( const std::string &topic )
{
if (topic.empty() || topic.size() > 65535) {
return false;
}
auto posHash = topic.find('#');
if (std::string::npos != posHash && posHash < topic.size() - 1) {
return false;
}
std::size_t pos = 0;
while ((pos = topic.find('+', pos)) != std::string::npos) {
if (pos > 0 && topic[pos - 1] != '/') {
return false;
}
if (pos < topic.size() - 1 && topic[pos + 1] != '/') {
return false;
}
++pos;
}
return true;
}
bool hasWildcard( const std::string &topic )
{
return ( topic.size() > 0 && (topic.find( '+' ) != std::string::npos || topic.size() - 1 == '#' ) );
}
bool testForOverlap( const std::string &existingTopic, const std::string &newTopic )
{
if (existingTopic == newTopic) {
return true;
}
// A topic that starts with a $ can never overlap with topic that does not start with a $.
// Topics that start!!! with a $ are so called system reserved topics and not meant for users to publish to.
if ((existingTopic[0] == '$' && newTopic[0] != '$') ||
(existingTopic[0] != '$' && newTopic[0] == '$')) {
return false;
}
std::vector<std::string> existingTopicList;
std::vector<std::string> newTopicList;
boost::algorithm::split(existingTopicList, existingTopic, [](char ch) { return ch == '/'; });
boost::algorithm::split(newTopicList, newTopic, [](char ch) { return ch == '/'; });
auto szExistingTopicList = existingTopicList.size();
auto szNewTopicList = newTopicList.size();
// Walk through the topic term by term until it is proved for certain that the topics either have no overlap
// or do have overlap.
for (std::size_t idx = 0; idx < std::minmax(szExistingTopicList, szNewTopicList).first; ++idx) {
if ("#" == existingTopicList[idx] || "#" == newTopicList[idx]) {
return true; // Match all wildcard found so there is always a possible overlap.
}
else if ("+" == existingTopicList[idx] || "+" == newTopicList[idx]) {
// these terms can match each other based on wildcard.
// Topics are still in the race for overlap, proceed to the next term
}
else if (existingTopicList[idx] != newTopicList[idx]) {
return false; // no match possible because terms are not wildcards and differ from each other.
}
else {
// term is an exact match. The topics are still in the race for overlap, proceed to the next term.
}
}
// Still no certain prove of overlap. If the number of terms for both topics are the same at this point then they overlap.
// If they are not the same than a match all wildcard on the longer topic can still make them match because of a special rule
// that states that a topic with a match all wildcard also matches a topic without that term.
// Example: topic /level/1 matches wildcard topic /level/1/#
// A match single wildcard at the end or at the term before a match all wildcard must also be taken into account.
// Example: /level/+ can overlap with /level/1/#
// /level/1 can overlap with /level/+/#
if (szNewTopicList != szExistingTopicList) {
if (szNewTopicList == szExistingTopicList + 1 && "#" == newTopicList[szNewTopicList - 1]) {
return (newTopicList[szNewTopicList - 2] == existingTopicList[szExistingTopicList - 1] || "+" == existingTopicList[szExistingTopicList - 1] || "+" == newTopicList[szNewTopicList - 2]);
}
if (szExistingTopicList == szNewTopicList + 1 && "#" == existingTopicList[szExistingTopicList - 1]) {
return (existingTopicList[szExistingTopicList - 2] == newTopicList[szNewTopicList - 1] || "+" == newTopicList[szNewTopicList - 1] || "+" == existingTopicList[szExistingTopicList - 2]);
}
return false;
}
return true;
}
std::string convertTopicToRegex(const std::string& topic)
{
// escape the regex characters in msgTemplate
static const boost::regex esc("[.^$|()\\[\\]{}*+?\\\\]");
static const std::string rep("\\\\$&"); // $&, refers to whatever is matched by the whole expression
std::string out = boost::regex_replace(topic, esc, rep);
static const boost::regex multiTopicRegex("#$");
static const boost::regex singleTopicRegex(R"((/|^|(?<=/))\\\+(/|$))");
out = boost::regex_replace(out, multiTopicRegex, ".*");
return boost::regex_replace(out, singleTopicRegex, "$1[^/]*?$2");
}
} // End namespace mqtt
} // End namespace components
} // End namespace osdev
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