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Added initial implementation of a 'topic_matcher' class.

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fpagliughi 2022-04-27 11:09:18 -04:00
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src/mqtt/topic_matcher.h Normal file
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/////////////////////////////////////////////////////////////////////////////
/// @file topic_matcher.h
/// Declaration of MQTT topic_matcher class
/// @date April 23, 2022
/// @author Frank Pagliughi
/////////////////////////////////////////////////////////////////////////////
/*******************************************************************************
* Copyright (c) 2022 Frank Pagliughi <fpagliughi@mindspring.com>
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v1.0 which accompany this distribution.
*
* The Eclipse Public License is available at
* http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Frank Pagliughi - initial implementation and documentation
*******************************************************************************/
#ifndef __mqtt_topic_matcher_h
#define __mqtt_topic_matcher_h
#include "mqtt/types.h"
#include "mqtt/topic.h"
#include <vector>
#include <map>
#include <forward_list>
#include <initializer_list>
#include <memory>
// The make_unique<>() template functions from the original std proposal:
// https://isocpp.org/files/papers/N3656.txt
#if __cplusplus < 201402L
namespace std {
template<class T> struct _Unique_if {
typedef unique_ptr<T> _Single_object;
};
template<class T> struct _Unique_if<T[]> {
typedef unique_ptr<T[]> _Unknown_bound;
};
template<class T, size_t N> struct _Unique_if<T[N]> {
typedef void _Known_bound;
};
template<class T, class... Args>
typename _Unique_if<T>::_Single_object
make_unique(Args&&... args) {
return unique_ptr<T>(new T(std::forward<Args>(args)...));
}
template<class T>
typename _Unique_if<T>::_Unknown_bound
make_unique(size_t n) {
typedef typename remove_extent<T>::type U;
return unique_ptr<T>(new U[n]());
}
template<class T, class... Args>
typename _Unique_if<T>::_Known_bound
make_unique(Args&&...) = delete;
}
#endif
namespace mqtt {
/////////////////////////////////////////////////////////////////////////////
/**
* This can be used to get an iterator to all items that have a filter that
* matches a topic. To test against a single filter, see
* [`TopicFilter`](crate::TopicFilter). This collection is more commonly
* used when there are a nuber of filters and each needs to be associated
* with a particular action or piece of data. Note, though, that a single
* incoming topic could match against several items in the collection. For
* example, the topic:
* data/temperature/engine
*
* Could match against the filters:
* data/temperature/# data/+/engine
*
* Thus, the collection gives an iterator for the items matching a topic.
*
* A common use for this would be to store callbacks to proces incoming
* messages based on topics.
*
* This code was adapted from the Eclipse Python `MQTTMatcher` class:
*
<https://github.com/eclipse/paho.mqtt.python/blob/master/src/paho/mqtt/matcher.py>
*
* which use a prefix tree (trie) to store the values.
*
* For example, if you had a `topic_mapper<int>` and you inserted:
* insert({"some/random/topic", 42})
* insert({"some/#", 99})
* insert({"some/+/topic", 33})
*
* The collection would be built like:
* "some" -> <null>
* "random" -> <null>
* "topic" -> <42>
* "#" -> <99>
* "+" -> <null>
* "topic" -> <33>
*/
template <typename T>
class topic_matcher
{
public:
using key_type = string;
using mapped_type = T;
using value_type = std::pair<key_type, mapped_type>;
using reference = value_type;
using const_reference = const value_type&;
private:
/**
* The nodes of the collection.
*/
struct node
{
using ptr_t = std::unique_ptr<node>;
using map_t = std::map<string, ptr_t>;
/** The value that matches the topic at this node, if any */
std::unique_ptr<value_type> content;
/** Child nodes mapped by the next field of the topic */
map_t children;
static ptr_t create() {
return std::make_unique<node>();
}
};
using node_ptr = typename node::ptr_t;
using node_map = typename node::map_t;
/** The root node of the collection */
node_ptr root_;
public:
class iterator {
/**
* Information about a node to search.
*/
struct search_node {
/** The current node being searched. null means end. */
node* node_;
/** The fields of the topic still to be searched. */
std::forward_list<string> syms_;
search_node() : node_(nullptr) {}
search_node(node* nd, const std::forward_list<string>& sy)
: node_(nd), syms_(sy) {}
search_node(node* nd, std::forward_list<string>&& sy)
: node_(nd), syms_(std::move(sy)) {}
};
/** The last-found value */
value_type* pval_;
/** The current search node */
search_node snode_;
/** The nodes still to be checked */
std::vector<search_node> nodes_;
/**
* Move the next iterator to the next value, or to end(), if none
* left.
*
* This will keep recursing until it finds a mtching node that
* contains a value or it reaches the end.
*/
void next() {
pval_ = nullptr;
// Can't move if we're already at the end
if (!snode_.node_)
return;
if (snode_.syms_.empty()) {
pval_ = snode_.node_->content.get();
}
else {
typename node_map::iterator child;
auto map_end = snode_.node_->children.end();
auto sym = snode_.syms_.front();
if ((child = snode_.node_->children.find(sym)) != map_end) {
auto syms = snode_.syms_;
syms.pop_front();
nodes_.push_back({child->second.get(), std::move(syms)});
}
if ((child = snode_.node_->children.find("+")) != map_end) {
auto syms = snode_.syms_;
syms.pop_front();
nodes_.push_back({child->second.get(), std::move(syms)});
}
if ((child = snode_.node_->children.find("#")) != map_end) {
pval_ = child->second->content.get();
}
}
if (!nodes_.empty()) {
// TODO: List pop_front()?
snode_ = nodes_.back();
nodes_.pop_back();
if (!pval_) {
// Recurse
return this->next();
}
}
else {
snode_ = search_node();
}
}
friend class topic_matcher;
iterator() : pval_(nullptr) {}
iterator(value_type* pval) : pval_(pval) {}
iterator(node* root, const string& topic) : pval_(nullptr) {
auto v = topic::split(topic);
std::forward_list<string> syms(v.begin(), v.end());
snode_ = search_node(root, std::move(syms));
next();
}
public:
/**
* Gets a reference to the current value.
* @return A reference to the current value.
*/
reference operator*() noexcept {
return *pval_;
}
/**
* Gets a const reference to the current value.
* @return A const reference to the current value.
*/
const_reference operator*() const noexcept {
return *pval_;
}
/**
* Get a pointer to the current value.
* @return A pointer to the current value.
*/
value_type* operator->() noexcept {
return pval_;
}
/**
* Get a const pointer to the current value.
* @return A const pointer to the current value.
*/
const value_type* operator->() const noexcept {
return pval_;
}
/**
* Postfix increment operator.
* @return An iterator pointing to the previous matching item.
*/
iterator operator++(int) noexcept {
auto tmp = *this;
this->next();
return tmp;
}
/**
* Prefix increment operator.
* @return An iterator pointing to the next matching item.
*/
iterator& operator++() noexcept {
this->next();
return *this;
}
/**
* Compares two iterators to see if they don't refer to the same
* node.
*
* @param other The other iterator to compare against this one.
* @return @em true if they don't match, @em false if they do
*/
bool operator!=(const iterator& other) const noexcept {
// TODO: Is this sufficient in the long run?
return pval_ != other.pval_ || snode_.node_ != other.snode_.node_;
}
};
/**
* A const iterator.
*/
class const_iterator : public iterator {
using base = iterator;
friend class topic_matcher;
const_iterator(iterator it) : base(it) {}
public:
/**
* Gets a const reference to the current value.
* @return A const reference to the current value.
*/
const_reference operator*() const noexcept {
return base::operator*();
}
/**
* Get a const pointer to the current value.
* @return A const pointer to the current value.
*/
const value_type* operator->() const noexcept {
return base::operator->();
}
};
/**
* Creates new, empty collection.
*/
topic_matcher()
: root_(node::create()) {}
/**
* Creates a new collection with a list of key/value pairs.
*
* This can be used to create a connection from a table of entries, as
* key/value pairs, like:
*
* topic_matcher<int> matcher {
* { "#", -1 },
* { "some/random/topic", 42 },
* { "some/#", 99 }
* }
*
* @param lst The list of key/value pairs to populate the collection.
*/
topic_matcher(std::initializer_list<value_type> lst)
: root_(node::create()) {
for (const auto& v : lst) {
insert(v);
}
}
/**
* Inserts a new key/value pair into the collection.
* @param val The value to place in the collection.
*/
void insert(value_type&& val) {
auto nd = root_.get();
auto fields = topic::split(val.first);
for (auto& field : fields) {
auto it = nd->children.find(field);
if (it == nd->children.end()) {
nd->children[field] = node::create();
it = nd->children.find(field);
}
nd = it->second.get();
}
nd->content = std::make_unique<value_type>(std::move(val));
}
/**
* Inserts a new value into the collection.
* @param key The topic/filter entry
* @param val The value to associate with that entry.
*/
void insert(const value_type& val) {
value_type v { val };
this->insert(std::move(v));
}
/**
* Gets a pointer to the value at the requested key.
* @param key The topic/filter entry to find.
* @return An iterator to the value if found, @em end() if not found.
*/
iterator find(const key_type& key) {
auto nd = root_.get();
auto fields = topic::split(key);
for (auto& field : fields) {
auto it = nd->children.find(field);
if (it == nd->children.end())
return end();
nd = it->second.get();
}
return iterator{ nd->content.get() };
}
/**
* Gets a const pointer to the value at the requested key.
* @param key The topic/filter entry to find.
* @return A const pointer to the value if found, @em nullptr if not
* found.
*/
const_iterator find(const key_type& key) const {
return const_cast<topic_matcher*>(this)->find(key);
}
/**
* Gets an iterator that can find the matches to the topic.
* @param topic The topic to search for matches.
* @return An iterator that can find the matches to the topic.
*/
iterator matches(const string& topic) {
return iterator(root_.get(), topic);
}
/**
* Gets a const iterator that can find the matches to the topic.
* @param topic The topic to search for matches.
* @return A const iterator that can find the matches to the topic.
*/
const_iterator matches(const string& topic) const {
return iterator(root_.get(), topic);
}
/**
* Gets an iterator for the end of the collection.
*
* This simply returns an empty/null iterator which we can use to signal
* the end of the collection.
*
* @return An empty/null iterator indicating the end of the collection.
*/
const_iterator end() const noexcept {
return iterator {};
}
/**
* Gets an iterator for the end of the collection.
*
* This simply returns an empty/null iterator which we can use to signal
* the end of the collection.
*
* @return An empty/null iterator indicating the end of the collection.
*/
const_iterator cend() const noexcept {
return iterator {};
}
};
/////////////////////////////////////////////////////////////////////////////
// end namespace mqtt
}
#endif // __mqtt_topic_matcher_h

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src/topic.cpp
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@ -28,24 +28,21 @@ namespace mqtt {
// This is just a string split around '/'
std::vector<string> topic::split(const string& s)
{
auto delim = '/';
std::vector<std::string> v;
if (s.empty())
return v;
using size_type = string::size_type;
const size_type npos = string::npos;
size_type startPos = 0, pos;
const auto delim = '/';
string::size_type startPos = 0, pos;
do {
pos = s.find(delim, startPos);
size_type n = (pos == npos) ? pos : (pos - startPos);
auto n = (pos == string::npos) ? pos : (pos - startPos);
v.push_back(s.substr(startPos, n));
startPos = pos + 1;
}
while (pos != npos);
while (pos != string::npos);
return v;
}

1
test/unit/CMakeLists.txt
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@ -43,6 +43,7 @@ add_executable(unit_tests unit_tests.cpp
test_string_collection.cpp
test_token.cpp
test_topic.cpp
test_topic_matcher.cpp
test_will_options.cpp
)

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test/unit/test_topic_matcher.cpp Normal file
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@ -0,0 +1,64 @@
// test_topic_matcher.cpp
//
// Unit tests for the topic_matcher class in the Paho MQTT C++ library.
//
/*******************************************************************************
* Copyright (c) 2022 Frank Pagliughi <fpagliughi@mindspring.com>
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v1.0 which accompany this distribution.
*
* The Eclipse Public License is available at
* http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
*******************************************************************************/
#define UNIT_TESTS
#include "catch2/catch.hpp"
#include "mqtt/topic_matcher.h"
#include <iostream>
using namespace mqtt;
/////////////////////////////////////////////////////////////////////////////
TEST_CASE("insert/get", "[topic_matcher]")
{
topic_matcher<int> matcher;
matcher.insert({"some/random/topic", 42});
auto it = matcher.find("some/random/topic");
REQUIRE(it != matcher.end());
REQUIRE(it->first == "some/random/topic");
REQUIRE(it->second == 42);
}
TEST_CASE("matcher matches", "[topic_matcher]")
{
topic_matcher<int> matcher {
{ "some/random/topic", 42 },
{ "some/#", 99 },
{ "some/other/topic", 55 },
{ "some/+/topic", 33 }
};
auto it = matcher.matches("some/random/topic");
for ( ; it != matcher.end(); ++it) {
std::cout << "Matcher got: '" << it->first << "' -> " << it->second << std::endl;
bool ok = (
(it->first == "some/random/topic" && it->second == 42) ||
(it->first == "some/#" && it->second == 99) ||
(it-> first == "some/+/topic" && it->second == 33)
);
REQUIRE(ok);
}
}