[core] Simplify asset:// implementation

* Move asset:// URL handling to DefaultFileSource.
* AssetFileSource implements FileSource interface and follows familiar implementation patterns.
* Move default implementation to platform/default, zip implementation to platform/android.
* Don't bother with modified / expires / etag -- assets are not cached so it doesn't matter.
* Don't bother with interleaving individual IO calls on the implementation thread. That adds a lot of complexity for very little benefit.

2 files changed, 26 insertions, 20 deletions

diff --git a/src/mbgl/storage/asset_context_base.hpp b/src/mbgl/storage/asset_context_base.hpp
deleted file mode 100644
index 92138615b5..0000000000
--- a/src/mbgl/storage/asset_context_base.hpp
+++ /dev/null
@@ -1,20 +0,0 @@
-#ifndef MBGL_STORAGE_ASSET_CONTEXT_BASE
-#define MBGL_STORAGE_ASSET_CONTEXT_BASE
-
-#include <mbgl/storage/request_base.hpp>
-
-namespace mbgl {
-
-class AssetContextBase {
-public:
-    static std::unique_ptr<AssetContextBase> createContext();
-
-    virtual ~AssetContextBase() = default;
-    virtual RequestBase* createRequest(const std::string& url,
-                                       RequestBase::Callback,
-                                       const std::string& assetRoot) = 0;
-};
-
-} // namespace mbgl
-
-#endif // MBGL_STORAGE_ASSET_CONTEXT_BASE
diff --git a/src/mbgl/storage/asset_file_source.hpp b/src/mbgl/storage/asset_file_source.hpp
new file mode 100644
index 0000000000..11a430e124
--- /dev/null
+++ b/src/mbgl/storage/asset_file_source.hpp
@@ -0,0 +1,26 @@
+#ifndef MBGL_STORAGE_ASSET_FILE_SOURCE
+#define MBGL_STORAGE_ASSET_FILE_SOURCE
+
+#include <mbgl/storage/file_source.hpp>
+
+namespace mbgl {
+
+namespace util {
+template <typename T> class Thread;
+} // namespace util
+
+class AssetFileSource : public FileSource {
+public:
+    AssetFileSource(const std::string& assetRoot);
+    ~AssetFileSource() override;
+
+    std::unique_ptr<FileRequest> request(const Resource&, Callback) override;
+
+private:
+    class Impl;
+    std::unique_ptr<util::Thread<Impl>> thread;
+};
+
+} // namespace mbgl
+
+#endif // MBGL_STORAGE_ASSET_FILE_SOURCE