juce_AudioThumbnailCache.cpp

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   By using JUCE, you agree to the terms of both the JUCE 7 End-User License
   Agreement and JUCE Privacy Policy.
 
   End User License Agreement: www.juce.com/juce-7-licence
   Privacy Policy: www.juce.com/juce-privacy-policy
 
   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
class AudioThumbnailCache::ThumbnailCacheEntry
{
public:
    ThumbnailCacheEntry (const int64 hashCode)
        : hash (hashCode),
          lastUsed (Time::getMillisecondCounter())
    {
    }
 
    ThumbnailCacheEntry (InputStream& in)
        : hash (in.readInt64()),
          lastUsed (0)
    {
        const int64 len = in.readInt64();
        in.readIntoMemoryBlock (data, (ssize_t) len);
    }
 
    void write (OutputStream& out)
    {
        out.writeInt64 (hash);
        out.writeInt64 ((int64) data.getSize());
        out << data;
    }
 
    int64 hash;
    uint32 lastUsed;
    MemoryBlock data;
 
private:
    JUCE_LEAK_DETECTOR (ThumbnailCacheEntry)
};
 
//==============================================================================
AudioThumbnailCache::AudioThumbnailCache (const int maxNumThumbs)
    : thread ("thumb cache"),
      maxNumThumbsToStore (maxNumThumbs)
{
    jassert (maxNumThumbsToStore > 0);
    thread.startThread (Thread::Priority::low);
}
 
AudioThumbnailCache::~AudioThumbnailCache()
{
}
 
AudioThumbnailCache::ThumbnailCacheEntry* AudioThumbnailCache::findThumbFor (const int64 hash) const
{
    for (int i = thumbs.size(); --i >= 0;)
        if (thumbs.getUnchecked (i)->hash == hash)
            return thumbs.getUnchecked (i);
 
    return nullptr;
}
 
int AudioThumbnailCache::findOldestThumb() const
{
    int oldest = 0;
    uint32 oldestTime = Time::getMillisecondCounter() + 1;
 
    for (int i = thumbs.size(); --i >= 0;)
    {
        const ThumbnailCacheEntry* const te = thumbs.getUnchecked (i);
 
        if (te->lastUsed < oldestTime)
        {
            oldest = i;
            oldestTime = te->lastUsed;
        }
    }
 
    return oldest;
}
 
bool AudioThumbnailCache::loadThumb (AudioThumbnailBase& thumb, const int64 hashCode)
{
    const ScopedLock sl (lock);
 
    if (ThumbnailCacheEntry* te = findThumbFor (hashCode))
    {
        te->lastUsed = Time::getMillisecondCounter();
 
        MemoryInputStream in (te->data, false);
        thumb.loadFrom (in);
        return true;
    }
 
    return loadNewThumb (thumb, hashCode);
}
 
void AudioThumbnailCache::storeThumb (const AudioThumbnailBase& thumb,
                                      const int64 hashCode)
{
    const ScopedLock sl (lock);
    ThumbnailCacheEntry* te = findThumbFor (hashCode);
 
    if (te == nullptr)
    {
        te = new ThumbnailCacheEntry (hashCode);
 
        if (thumbs.size() < maxNumThumbsToStore)
            thumbs.add (te);
        else
            thumbs.set (findOldestThumb(), te);
    }
 
    {
        MemoryOutputStream out (te->data, false);
        thumb.saveTo (out);
    }
 
    saveNewlyFinishedThumbnail (thumb, hashCode);
}
 
void AudioThumbnailCache::clear()
{
    const ScopedLock sl (lock);
    thumbs.clear();
}
 
void AudioThumbnailCache::removeThumb (const int64 hashCode)
{
    const ScopedLock sl (lock);
 
    for (int i = thumbs.size(); --i >= 0;)
        if (thumbs.getUnchecked (i)->hash == hashCode)
            thumbs.remove (i);
}
 
static int getThumbnailCacheFileMagicHeader() noexcept
{
    return (int) ByteOrder::littleEndianInt ("ThmC");
}
 
bool AudioThumbnailCache::readFromStream (InputStream& source)
{
    if (source.readInt() != getThumbnailCacheFileMagicHeader())
        return false;
 
    const ScopedLock sl (lock);
    clear();
    int numThumbnails = jmin (maxNumThumbsToStore, source.readInt());
 
    while (--numThumbnails >= 0 && ! source.isExhausted())
        thumbs.add (new ThumbnailCacheEntry (source));
 
    return true;
}
 
void AudioThumbnailCache::writeToStream (OutputStream& out)
{
    const ScopedLock sl (lock);
 
    out.writeInt (getThumbnailCacheFileMagicHeader());
    out.writeInt (thumbs.size());
 
    for (int i = 0; i < thumbs.size(); ++i)
        thumbs.getUnchecked (i)->write (out);
}
 
void AudioThumbnailCache::saveNewlyFinishedThumbnail (const AudioThumbnailBase&, int64)
{
}
 
bool AudioThumbnailCache::loadNewThumb (AudioThumbnailBase&, int64)
{
    return false;
}
 
} // namespace juce