CodecRegistry.cpp

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//
// C++ Implementation: Audio::CodecRegistry, Audio::CodecRegistration
//

#include "CodecRegistry.h"
#include "codecs/Codec.h"
#include "config.h"

#include <algorithm>
#include <iostream>

template<> Audio::CodecRegistry* Singleton<Audio::CodecRegistry>::_singletonInstance = 0;

namespace Audio {

    CodecRegistry::CodecRegistry() throw()
    {
    }
    
    CodecRegistry::~CodecRegistry()
    {
        nameCodec.clear();
        universalCodecs.clear();
        extensionCodecs.clear();
        
        for (CodecPriority::const_iterator it = codecPriority.begin(); it != codecPriority.end(); ++it)
            delete it->first;
        codecPriority.clear();
    }
    
    void CodecRegistry::add(Codec* codec, int priority) throw()
    {
        if (codecPriority.find(codec) == codecPriority.end()) {
            codecPriority[codec] = priority;
            nameCodec[codec->getName()] = codec;
            
            std::cout << "Registering codec " << codec->getName().c_str();
            
            const Codec::Extensions *ext = codec->getExtensions();
            if (ext) {
                for (Codec::Extensions::const_iterator it = ext->begin(); it != ext->end(); ++it) {
                    std::cout << " " << it->c_str();
                    extensionCodecs[*it].insert(codec);
                }
            } else {
                std::cout << " as universal";
                universalCodecs.insert(codec);
            }
            
            std::cout << "." << std::endl;
        } else {
            std::cout << "Codec " << codec->getName().c_str() << " already registered" << std::endl;
        }
    }
    
    void CodecRegistry::remove(Codec* codec) throw()
    {
        if (codecPriority.find(codec) != codecPriority.end()) {
            codecPriority.erase(codec);
            nameCodec.erase(codec->getName());
            const Codec::Extensions *ext = codec->getExtensions();
            if (ext) {
                for (Codec::Extensions::const_iterator it = ext->begin(); it != ext->end(); ++it) 
                    extensionCodecs[*it].erase(codec);
            } else {
                universalCodecs.erase(codec);
            }
        }
    }
    
    Codec* CodecRegistry::findByName(const std::string& name) const throw(CodecNotFoundException)
    {
        NameCodec::const_iterator it = nameCodec.find(name);
        if (it != nameCodec.end())
            return it->second; else
            throw CodecNotFoundException(
                std::string("No codec with name \"") + name + "\" has been registered");
    }
    
    template<typename INDEX, typename T>
    class MappedComparator
    {
        const INDEX& _index;
    public: 
        MappedComparator(const INDEX& index) : _index(index) {}
        bool operator()(const T& a, const T& b) const
        {
            typename INDEX::const_iterator ait = _index.find(a);
            typename INDEX::const_iterator bit = _index.find(b);
            if (ait == _index.end()) {
                return (bit != _index.end());
            } else {
                if (bit == _index.end()) {
                    return false;
                } else {
                    return (*ait < *bit);
                }
            }
        }
    };
    
    Codec* CodecRegistry::findByFile(const std::string& path, VSFileSystem::VSFileType type) const throw(CodecNotFoundException)
    {
        std::vector<Codec*> candidates;
        
        // NOTE: we'll assume that if they are including the specified extension, they'll return
        //      true if asked if they can handle the file with !canOpen.
        size_t sep = path.find_last_of('.');
        if (sep != std::string::npos && (sep+1) < path.length()) {
            ExtensionCodecs::const_iterator eit = extensionCodecs.find(
                path.substr(sep+1, std::string::npos));
            if (eit != extensionCodecs.end())
                for (CodecSet::const_iterator esit=eit->second.begin(); esit != eit->second.end(); ++esit) 
                    candidates.push_back(*esit);
        }
        
        for (CodecSet::const_iterator uit = universalCodecs.begin(); uit != universalCodecs.end(); ++uit)
            if ((*uit)->canHandle(path, false, type))
                candidates.push_back(*uit);
        
        // Now we'll sort candidates by priority, and return the first codec that can actually handle the file.
        if (candidates.begin() != candidates.end()) {
            std::sort(
                candidates.begin(), 
                candidates.end(), 
                MappedComparator<CodecPriority,Codec*>(codecPriority));

            // Why do we need an explicit cast *to* const?
            // See http://www.mpi-inf.mpg.de/~hitoshi/otherprojects/tips/cpp-memo.shtml
            for (std::vector<Codec*>::const_reverse_iterator it = candidates.rbegin();
                    it != reinterpret_cast<const std::vector<Codec*> &>(candidates).rend(); ++it)
                if ((*it)->canHandle(path, true, type))
                    return *it;
        }
    
        // No candidate is able to handle this one!
        throw CodecNotFoundException(
            std::string("No registered codec can handle the file \"") + path + "\"");
    }
    
    Stream* CodecRegistry::open(const std::string& path, VSFileSystem::VSFileType type) const 
        throw(Exception)
    {
        Codec *codec = findByFile(path, type);
        return codec->open(path, type);
    }
    
    CodecRegistration::CodecRegistration(Codec* _codec, int priority) throw()
        : codec(_codec)
    {
        if (!CodecRegistry::getSingleton())
            new CodecRegistry();
        CodecRegistry::getSingleton()->add(codec);
    }
    
    CodecRegistration::~CodecRegistration()
    {
        CodecRegistry::getSingleton()->remove(codec);
    }

};