[core] Add method for setting a maximum size for the ambient cache

- Removed this parameter from the constructor, now that we
  have a method to set it.
- Add the method and enforce the limits if the ambient cache exceeds the
  size.

1 files changed, 24 insertions, 6 deletions

diff --git a/include/mbgl/storage/default_file_source.hpp b/include/mbgl/storage/default_file_source.hpp
index ddbdab8cf3..f46f41771e 100644
--- a/include/mbgl/storage/default_file_source.hpp
+++ b/include/mbgl/storage/default_file_source.hpp
@@ -30,12 +30,8 @@ public:
      * regions, we want the database to remain fairly small (order tens or low hundreds
      * of megabytes).
      */
-    DefaultFileSource(const std::string& cachePath,
-                      const std::string& assetPath,
-                      uint64_t maximumCacheSize = util::DEFAULT_MAX_CACHE_SIZE);
-    DefaultFileSource(const std::string& cachePath,
-                      std::unique_ptr<FileSource>&& assetFileSource,
-                      uint64_t maximumCacheSize = util::DEFAULT_MAX_CACHE_SIZE);
+    DefaultFileSource(const std::string& cachePath, const std::string& assetPath);
+    DefaultFileSource(const std::string& cachePath, std::unique_ptr<FileSource>&& assetFileSource);
     ~DefaultFileSource() override;
 
     bool supportsCacheOnlyRequests() const override {
@@ -220,6 +216,28 @@ public:
      */
     void clearAmbientCache(std::function<void (std::exception_ptr)>);
 
+    /*
+     * Sets the maximum size in bytes for the ambient cache.
+     *
+     * This call is potentially expensive because it will try
+     * to trim the data in case the database is larger than the
+     * size defined. The size of offline regions are not affected
+     * by this settings, but the ambient cache will always try
+     * to not exceed the maximum size defined, taking into account
+     * the current size for the offline regions.
+     *
+     * If the maximum size is set to 50 MB and 40 MB are already
+     * used by offline regions, the cache size will be effectively
+     * 10 MB.
+     *
+     * Setting the size to 0 will disable the cache if there is no
+     * offline region on the database.
+     *
+     * This method should always be called before using the database,
+     * otherwise the default maximum size will be used.
+     */
+    void setMaximumAmbientCacheSize(uint64_t size, std::function<void (std::exception_ptr)> callback);
+
     // For testing only.
     void setOnlineStatus(bool);