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msd2/tracking/piwik/vendor/szymach/c-pchart/doc/cache.md

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+# Cache operations
+
+[Reference](http://wiki.pchart.net/doc.pcache.pcache.html)
+
+To speed up the process of creating charts, you can store them in the cache files
+using the `CpChart\Chart\Cache` class. It will create two files - `cache.db` and
+`index.db` in a dedicated directory (`app\cache` by default, relative to the library's
+root directory), but you can change these using the `$settings` array passed
+to the object's constructor.
+
+Should you decide to use the cache component, the following sections describe
+how you can do that.
+
+## Using cache to store and retrieve chart data
+
+```php
+require '/path/to/your/vendor/autoload.php';
+
+use CpChart\Chart\Cache;
+use CpChart\Chart\Data;
+use CpChart\Chart\Image;
+
+// Standard chart creation
+$data = new Data();
+$data->addPoints([1, 3, 4, 3, 5]);
+
+$image = new Image(700, 230, $data);
+$image->setFontProperties(["FontName" => "Forgotte.ttf", "FontSize" => 11]);
+$image->setGraphArea(60, 40, 670, 190);
+$image->drawScale();
+$image->drawSplineChart();
+$image->drawGradientArea(0, 0, 700, 20, DIRECTION_VERTICAL, [
+    "StartR" => 0,
+    "StartG" => 0,
+    "StartB" => 0,
+    "EndR" => 50,
+    "EndG" => 50,
+    "EndB" => 50,
+    "Alpha" => 100
+]);
+$image->setFontProperties(["FontName" => "Silkscreen.ttf", "FontSize" => 6]);
+$image->drawText(10, 13, "Test of the pCache class", ["R" => 255, "G" => 255, "B" => 255]);
+
+// Create a cache object and store the chart in it
+$cache = new Cache([
+    // Optionally change the default directory and file names
+    'CacheFolder' => 'path/to/your/cache/directory',
+    'CacheIndex' => 'name_of_the_index_file.db',
+    'CacheDB' => 'name_of_the_database_file.db'
+]);
+$chartHash = $cache->getHash($data); // Chart dentifier in the cache
+$cache->writeToCache($chartHash, $image);
+
+// Create an image file from cache
+$cache->saveFromCache($chartHash, "example.drawCachedSpline.png");
+
+// Directly stroke the saved data to the browser
+$cache->strokeFromCache($chartHash)
+
+// Automatically choose a way to output stored data
+$cache->autoOutput($chartHash)
+```
+
+## Removal operations
+
+```php
+// Assuming we have $chartHash and $cache variables from the previous example
+
+// This will remove the chart by it's hash
+$cache->remove($chartHash);
+
+// This will remove every chart in cache older than the amount of seconds passed
+// into the argument's parameter
+$cache->removeOlderThan(60 * 60 * 24); // Remove data older than 24 hours
+
+// This flushes the cache completely and regenerates the .db files
+$cache->flush();
+```
+
+There is also the function called `CpChart\Chart\Cache::dbRemoval(array $settings)`,
+but it only covers two use cases - removing by chart hash and age. Since there
+are dedicated methods for each of them (`remove` and `removeOlderThan`, respectively),
+there is no reason to cover it any further.