QString loadTranslatedDocument(KSharedDataCache *cache) {

  // Find the data
  QByteArray document;

  if (!cache->find("translated-doc-template", &document)) {
    // Entry is not cached, manually generate and then add to cache.
    document = translateDocument(globalTemplate());
    cache->insert(document);
  }

  // Don't forget to encode/decode properly
  return QString::fromUtf8(document);
}

Member Function Documentation

KSharedDataCache::KSharedDataCache(const QString &cacheName, unsigned int defaultCacheSize, unsigned int expectedItemSize = 0)

Attaches to a shared cache, creating it if necessary. If supported, this data cache will be shared across all processes using this cache (with subsequent memory savings). If shared memory is unsupported or a failure occurs, caching will still be supported, but only in the same process, and only using the same KSharedDataCache object.

cacheName Name of the cache to use/share. defaultCacheSize Amount of data to be able to store, in bytes. The actual size will be slightly larger on disk due to accounting overhead. If the cache already existed then it <em>will not</em> be resized. For this reason you should specify some reasonable size. expectedItemSize The average size of an item that would be stored in the cache, in bytes. Choosing an average size of zero bytes causes KSharedDataCache to use whatever it feels is the best default for the system.

void KSharedDataCache::clear()

Removes all entries from the cache.

bool KSharedDataCache::contains(const QString &key) const

Returns true if the cache currently contains the image for the given filename.

NOTE: Calling this function is threadsafe, but it is in general not possible to guarantee the image stays cached immediately afterwards, so if you need the result use find().

[static] void KSharedDataCache::deleteCache(const QString &cacheName)

Removes the underlying file from the cache. Note that this is *all* that this function does. The shared memory segment is still attached and will still contain all the data until all processes currently attached remove the mapping.

In order to remove the data see clear().

KSharedDataCache::EvictionPolicy KSharedDataCache::evictionPolicy() const

Returns the removal policy in use by the shared cache.

See also setEvictionPolicy() and EvictionPolicy.

bool KSharedDataCache::find(const QString &key, QByteArray *destination) const

Returns the data in the cache named by key (even if it's some other process's data named with the same key!), stored in destination. If there is no entry named by key then destination is left unchanged. The return value is used to tell what happened.

If you simply want to verify whether an entry is present in the cache then see contains().

key The key to find in the cache.

destination Is set to the value of key in the cache if key is present, left unchanged otherwise.

Returns true if key was present in the cache (destination will also be updated), false if key was not present (destination will be unchanged).

unsigned int KSharedDataCache::freeSize() const

Returns the amount of free space in the cache, in bytes. Due to implementation details it is possible to still not be able to fit an entry in the cache at any given time even if it is smaller than the amount of space remaining.

bool KSharedDataCache::insert(const QString &key, const QByteArray &data)

Attempts to insert the entry data into the shared cache, named by key, and returns true only if successful.

Note that even if the insert was successful, that the newly added entry may be evicted by other processes contending for the cache.

void KSharedDataCache::setEvictionPolicy(KSharedDataCache::EvictionPolicy newPolicy)

Sets the entry removal policy for the shared cache to newPolicy. The default is EvictionPolicy::NoEvictionPreference.

See also evictionPolicy() and EvictionPolicy.

[since 4.6] void KSharedDataCache::setTimestamp(unsigned int newTimestamp)

Sets the shared timestamp of the cache. Timestamping is supported to allow applications to more effectively "version" the data stored in the cache. However, the timestamp is shared with <em>all</em> applications using the cache so you should always be prepared for invalid timestamps.

When the cache is first created (note that this is different from attaching to an existing shared cache on disk), the cache timestamp is initialized to the time returned by time(2). KSharedDataCache will not update the timestamp again, it is only updated through this method.

Example:

QImage loadCachedImage(const QString &key)
{
    // Check timestamp
    if (m_sharedCache->timestamp() < m_currentThemeTimestamp) {
        // Cache is stale, clean it out.
        m_sharedCache->clear();
        m_sharedCache->setTimestamp(m_currentThemeTimestamp);
    }

    // Check cache and load image as usual...
}

newTimestamp The new timestamp to mark the shared cache with.

This function was introduced in 4.6.

See also timestamp().

[since 4.6] unsigned int KSharedDataCache::timestamp() const

Returns The shared timestamp of the cache. The interpretation of the timestamp returned is up to the application. KSharedDataCache will initialize the timestamp to the time returned by time(2) on cache creation, but KSharedDataCache will not touch the timestamp again.

This function was introduced in 4.6.

See also setTimestamp().

unsigned int KSharedDataCache::totalSize() const

Returns the usable cache size in bytes. The actual amount of memory used will be slightly larger than this to account for required accounting overhead.