1 files changed, 465 insertions, 0 deletions
diff --git a/src/lib/util/state_model.cc b/src/lib/util/state_model.cc
new file mode 100644
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+++ b/src/lib/util/state_model.cc
@@ -0,0 +1,465 @@
+// Copyright (C) 2013-2020 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include <config.h>
+#include <util/state_model.h>
+#include <string>
+
+namespace isc {
+namespace util {
+
+/********************************** State *******************************/
+
+State::State(const int value, const std::string& label, StateHandler handler,
+             const StatePausing& state_pausing)
+    : LabeledValue(value, label), handler_(handler), pausing_(state_pausing),
+      was_paused_(false) {
+}
+
+State::~State() {
+}
+
+void
+State::run() {
+    (handler_)();
+}
+
+bool
+State::shouldPause() {
+    if ((pausing_ == STATE_PAUSE_ALWAYS) ||
+        ((pausing_ == STATE_PAUSE_ONCE) && (!was_paused_))) {
+        was_paused_ = true;
+        return (true);
+    }
+    return (false);
+}
+
+/********************************** StateSet *******************************/
+
+StateSet::StateSet() {
+}
+
+StateSet::~StateSet() {
+}
+
+void
+StateSet::add(const int value, const std::string& label, StateHandler handler,
+              const StatePausing& state_pausing) {
+    try {
+        LabeledValueSet::add(LabeledValuePtr(new State(value, label, handler,
+                                                       state_pausing)));
+    } catch (const std::exception& ex) {
+        isc_throw(StateModelError, "StateSet: cannot add state :" << ex.what());
+    }
+
+}
+
+const StatePtr
+StateSet::getState(int value) {
+    if (!isDefined(value)) {
+        isc_throw(StateModelError," StateSet: state is undefined");
+    }
+
+    // Since we have to use dynamic casting, to get a state pointer
+    // we can't return a reference.
+    StatePtr state = boost::dynamic_pointer_cast<State>(get(value));
+    return (state);
+}
+
+/********************************** StateModel *******************************/
+
+
+// Common state model states
+const int StateModel::NEW_ST;
+const int StateModel::END_ST;
+
+const int StateModel::SM_DERIVED_STATE_MIN;
+
+// Common state model events
+const int StateModel::NOP_EVT;
+const int StateModel::START_EVT;
+const int StateModel::END_EVT;
+const int StateModel::FAIL_EVT;
+
+const int StateModel::SM_DERIVED_EVENT_MIN;
+
+StateModel::StateModel() : events_(), states_(), dictionaries_initted_(false),
+                           curr_state_(NEW_ST), prev_state_(NEW_ST),
+                           last_event_(NOP_EVT), next_event_(NOP_EVT),
+                           on_entry_flag_(false), on_exit_flag_(false),
+                           paused_(false), mutex_(new std::mutex) {
+}
+
+StateModel::~StateModel(){
+}
+
+void
+StateModel::startModel(const int start_state) {
+    // Initialize dictionaries of events and states.
+    initDictionaries();
+
+    // Set the current state to starting state and enter the run loop.
+    setState(start_state);
+
+    // Start running the model.
+    runModel(START_EVT);
+}
+
+void
+StateModel::runModel(unsigned int run_event) {
+    /// If the dictionaries aren't built bail out.
+    if (!dictionaries_initted_) {
+        abortModel("runModel invoked before model has been initialized");
+    }
+
+    try {
+        // Seed the loop with the given event as the next to process.
+        postNextEvent(run_event);
+        do {
+            // Invoke the current state's handler.  It should consume the
+            // next event, then determine what happens next by setting
+            // current state and/or the next event.
+            getState(curr_state_)->run();
+
+            // Keep going until a handler sets next event to a NOP_EVT.
+        } while (!isModelDone() && getNextEvent() != NOP_EVT);
+    } catch (const std::exception& ex) {
+        // The model has suffered an unexpected exception. This constitutes
+        // a model violation and indicates a programmatic shortcoming.
+        // In theory, the model should account for all error scenarios and
+        // deal with them accordingly.  Transition to END_ST with FAILED_EVT
+        // via abortModel.
+        abortModel(ex.what());
+    }
+}
+
+void
+StateModel::nopStateHandler() {
+}
+
+void
+StateModel::initDictionaries() {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    if (dictionaries_initted_) {
+        isc_throw(StateModelError, "Dictionaries already initialized");
+    }
+    // First let's build and verify the dictionary of events.
+    try {
+        defineEvents();
+        verifyEvents();
+    } catch (const std::exception& ex) {
+        isc_throw(StateModelError, "Event set is invalid: " << ex.what());
+    }
+
+    // Next let's build and verify the dictionary of states.
+    try {
+        defineStates();
+        verifyStates();
+    } catch (const std::exception& ex) {
+        isc_throw(StateModelError, "State set is invalid: " << ex.what());
+    }
+
+    // Record that we are good to go.
+    dictionaries_initted_ = true;
+}
+
+void
+StateModel::defineEvent(unsigned int event_value, const std::string& label) {
+    if (!isModelNewInternal()) {
+        // Don't allow for self-modifying models.
+        isc_throw(StateModelError, "Events may only be added to a new model."
+                   << event_value << " - " << label);
+    }
+
+    // Attempt to add the event to the set.
+    try {
+        events_.add(event_value, label);
+    } catch (const std::exception& ex) {
+        isc_throw(StateModelError, "Error adding event: " << ex.what());
+    }
+}
+
+const EventPtr&
+StateModel::getEvent(unsigned int event_value) {
+    if (!events_.isDefined(event_value)) {
+        isc_throw(StateModelError,
+                  "Event value is not defined:" << event_value);
+    }
+
+    return (events_.get(event_value));
+}
+
+void
+StateModel::defineState(unsigned int state_value, const std::string& label,
+                        StateHandler handler, const StatePausing& state_pausing) {
+    if (!isModelNewInternal()) {
+        // Don't allow for self-modifying maps.
+        isc_throw(StateModelError, "States may only be added to a new model."
+                   << state_value << " - " << label);
+    }
+
+    // Attempt to add the state to the set.
+    try {
+        states_.add(state_value, label, handler, state_pausing);
+    } catch (const std::exception& ex) {
+        isc_throw(StateModelError, "Error adding state: " << ex.what());
+    }
+}
+
+const StatePtr
+StateModel::getState(unsigned int state_value) {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return getStateInternal(state_value);
+}
+
+const StatePtr
+StateModel::getStateInternal(unsigned int state_value) {
+    if (!states_.isDefined(state_value)) {
+        isc_throw(StateModelError,
+                  "State value is not defined:" << state_value);
+    }
+
+    return (states_.getState(state_value));
+}
+
+void
+StateModel::defineEvents() {
+    defineEvent(NOP_EVT, "NOP_EVT");
+    defineEvent(START_EVT, "START_EVT");
+    defineEvent(END_EVT, "END_EVT");
+    defineEvent(FAIL_EVT, "FAIL_EVT");
+}
+
+void
+StateModel::verifyEvents() {
+    getEvent(NOP_EVT);
+    getEvent(START_EVT);
+    getEvent(END_EVT);
+    getEvent(FAIL_EVT);
+}
+
+void
+StateModel::defineStates() {
+    defineState(NEW_ST, "NEW_ST",
+                std::bind(&StateModel::nopStateHandler, this));
+    defineState(END_ST, "END_ST",
+                std::bind(&StateModel::nopStateHandler, this));
+}
+
+void
+StateModel::verifyStates() {
+    getStateInternal(NEW_ST);
+    getStateInternal(END_ST);
+}
+
+void
+StateModel::onModelFailure(const std::string&) {
+    // Empty implementation to make deriving classes simpler.
+}
+
+void
+StateModel::transition(unsigned int state, unsigned int event) {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    setStateInternal(state);
+    postNextEventInternal(event);
+}
+
+void
+StateModel::endModel() {
+    transition(END_ST, END_EVT);
+}
+
+void
+StateModel::unpauseModel() {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    paused_ = false;
+}
+
+void
+StateModel::abortModel(const std::string& explanation) {
+    transition(END_ST, FAIL_EVT);
+
+    std::ostringstream stream ;
+    stream << explanation << " : " << getContextStr();
+    onModelFailure(stream.str());
+}
+
+void
+StateModel::setState(unsigned int state) {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    setStateInternal(state);
+}
+
+void
+StateModel::setStateInternal(unsigned int state) {
+    if (state != END_ST && !states_.isDefined(state)) {
+        isc_throw(StateModelError,
+                  "Attempt to set state to an undefined value: " << state );
+    }
+
+    prev_state_ = curr_state_;
+    curr_state_ = state;
+
+    // Set the "do" flags if we are transitioning.
+    on_entry_flag_ = ((state != END_ST) && (prev_state_ != curr_state_));
+
+    // At this time they are calculated the same way.
+    on_exit_flag_ = on_entry_flag_;
+
+    // If we're entering the new state we need to see if we should
+    // pause the state model in this state.
+    if (on_entry_flag_ && !paused_ && getStateInternal(state)->shouldPause()) {
+        paused_ = true;
+    }
+}
+
+void
+StateModel::postNextEvent(unsigned int event_value) {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    postNextEventInternal(event_value);
+}
+
+void
+StateModel::postNextEventInternal(unsigned int event_value) {
+    // Check for FAIL_EVT as special case of model error before events are
+    // defined.
+    if (event_value != FAIL_EVT && !events_.isDefined(event_value)) {
+        isc_throw(StateModelError,
+                  "Attempt to post an undefined event, value: " << event_value);
+    }
+
+    last_event_ = next_event_;
+    next_event_ = event_value;
+}
+
+bool
+StateModel::doOnEntry() {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    bool ret = on_entry_flag_;
+    on_entry_flag_ = false;
+    return (ret);
+}
+
+bool
+StateModel::doOnExit() {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    bool ret = on_exit_flag_;
+    on_exit_flag_ = false;
+    return (ret);
+}
+
+unsigned int
+StateModel::getCurrState() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return (curr_state_);
+}
+
+unsigned int
+StateModel::getPrevState() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return (prev_state_);
+}
+
+unsigned int
+StateModel::getLastEvent() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return (last_event_);
+}
+
+unsigned int
+StateModel::getNextEvent() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return (next_event_);
+}
+
+bool
+StateModel::isModelNew() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return isModelNewInternal();
+}
+
+bool
+StateModel::isModelNewInternal() const {
+    return (curr_state_ == NEW_ST);
+}
+
+bool
+StateModel::isModelRunning() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return ((curr_state_ != NEW_ST) && (curr_state_ != END_ST));
+}
+
+bool
+StateModel::isModelWaiting() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return ((curr_state_ != NEW_ST) && (curr_state_ != END_ST) &&
+            (next_event_ == NOP_EVT));
+}
+
+bool
+StateModel::isModelDone() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return (curr_state_ == END_ST);
+}
+
+bool
+StateModel::didModelFail() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return ((curr_state_ == END_ST) && (next_event_ == FAIL_EVT));
+}
+
+bool
+StateModel::isModelPaused() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return (paused_);
+}
+
+std::string
+StateModel::getStateLabel(const int state) const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return getStateLabelInternal(state);
+}
+
+std::string
+StateModel::getStateLabelInternal(const int state) const {
+    return (states_.getLabel(state));
+}
+
+std::string
+StateModel::getEventLabel(const int event) const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    return getEventLabelInternal(event);
+}
+
+std::string
+StateModel::getEventLabelInternal(const int event) const {
+    return (events_.getLabel(event));
+}
+
+std::string
+StateModel::getContextStr() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    std::ostringstream stream;
+    stream << "current state: [ "
+            << curr_state_ << " " << getStateLabelInternal(curr_state_)
+            << " ] next event: [ "
+            << next_event_ << " " << getEventLabelInternal(next_event_) << " ]";
+    return (stream.str());
+}
+
+std::string
+StateModel::getPrevContextStr() const {
+    std::lock_guard<std::mutex> lock(*mutex_);
+    std::ostringstream stream;
+    stream << "previous state: [ "
+           << prev_state_ << " " << getStateLabelInternal(prev_state_)
+           << " ] last event: [ "
+           << next_event_ << " " << getEventLabelInternal(last_event_) << " ]";
+    return (stream.str());
+}
+
+} // namespace isc::util
+} // namespace isc