annotate base/ById.cpp @ 1752:6d09d68165a4 by-id

Further review of ById: make IDs only available when adding a model to the ById store, not by querying the item directly. This means any id encountered in the wild must have been added to the store at some point (even if later released), which simplifies reasoning about lifecycles

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    
    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 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#include "ById.h"

#include <unordered_map>
#include <typeinfo>

int IdAlloc::getNextId()
{
    static int nextId = 0;
    static QMutex mutex;
    QMutexLocker locker(&mutex);
    int i = nextId;
    if (nextId == INT_MAX) {
        nextId = INT_MIN;
    } else {
        ++nextId;
        if (nextId == 0 || nextId == NO_ID) {
            throw std::runtime_error("Internal ID limit exceeded!");
        }
    }
    return i;
}

class AnyById::Impl
{
public:    
    ~Impl() {
        QMutexLocker locker(&m_mutex);
        bool empty = true;
        for (const auto &p: m_items) {
            if (p.second && p.second.use_count() > 0) {
                empty = false;
                break;
            }
        }
        if (!empty) {
            SVCERR << "WARNING: ById map is not empty at close; some items have not been released" << endl;
            SVCERR << "         Unreleased items are:" << endl;
            for (const auto &p: m_items) {
                if (p.second && p.second.use_count() > 0) {
                    SVCERR << "         - id #" << p.first
                           << ": type " << typeid(*p.second.get()).name()
                           << ", use count " << p.second.use_count() << endl;
                }
            }
        }
    }
        
    int add(std::shared_ptr<WithId> item) {
        int id = item->getUntypedId();
        if (id == IdAlloc::NO_ID) {
            throw std::logic_error("item id should never be NO_ID");
        }
        QMutexLocker locker(&m_mutex);
        if (m_items.find(id) != m_items.end()) {
            SVCERR << "ById::add: item with id " << id
                   << " is already recorded (existing item type is "
                   << typeid(*m_items.find(id)->second.get()).name()
                   << ", proposed is "
                   << typeid(*item.get()).name() << ")" << endl;
            throw std::logic_error("item id is already recorded in add");
        }
        m_items[id] = item;
        return id;
    }

    void release(int id) {
        if (id == IdAlloc::NO_ID) {
            return;
        }
        SVCERR << "ById::release(" << id << ")" << endl;
        QMutexLocker locker(&m_mutex);
        if (m_items.find(id) == m_items.end()) {
            SVCERR << "ById::release: unknown item id " << id << endl;
            throw std::logic_error("unknown item id in release");
        }
        m_items.erase(id);
    }
    
    std::shared_ptr<WithId> get(int id) const {
        if (id == IdAlloc::NO_ID) {
            return {}; // this id cannot be added: avoid locking
        }
        QMutexLocker locker(&m_mutex);
        const auto &itr = m_items.find(id);
        if (itr != m_items.end()) {
            return itr->second;
        } else {
            return {};
        }
    }

private:
    mutable QMutex m_mutex;
    std::unordered_map<int, std::shared_ptr<WithId>> m_items;
};

int
AnyById::add(std::shared_ptr<WithId> item)
{
    return impl().add(item);
}

void
AnyById::release(int id)
{
    impl().release(id);
}

std::shared_ptr<WithId>
AnyById::get(int id)
{
    return impl().get(id);
}

AnyById::Impl &
AnyById::impl()
{
    static Impl impl;
    return impl;
}