1 files changed, 111 insertions, 0 deletions
diff --git a/src/mbgl/tile/tile_source_impl.hpp b/src/mbgl/tile/tile_source_impl.hpp
new file mode 100644
index 0000000000..8d5caeb829
--- /dev/null
+++ b/src/mbgl/tile/tile_source_impl.hpp
@@ -0,0 +1,111 @@
+#pragma once
+
+#include <mbgl/tile/tile_source.hpp>
+#include <mbgl/storage/file_source.hpp>
+#include <mbgl/style/update_parameters.hpp>
+#include <mbgl/util/tileset.hpp>
+
+#include <cassert>
+
+namespace mbgl {
+
+template <typename T>
+TileSource<T>::TileSource(T& tileData_,
+                          const OverscaledTileID& id,
+                          const style::UpdateParameters& parameters,
+                          const Tileset& tileset)
+    : tileData(tileData_),
+      necessity(Necessity::Optional),
+      resource(Resource::tile(
+        tileset.tiles.at(0),
+        parameters.pixelRatio,
+        id.canonical.x,
+        id.canonical.y,
+        id.canonical.z)),
+      fileSource(parameters.fileSource) {
+    assert(!request);
+    if (fileSource.supportsOptionalRequests()) {
+        // When supported, the first request is always optional, even if the TileSource
+        // is marked as required. That way, we can let the first optional request continue
+        // to load when the TileSource is later changed from required to optional. If we
+        // started out with a required request, we'd have to cancel everything, including the
+        // initial optional part of the request.
+        loadOptional();
+    } else {
+        // When the FileSource doesn't support optional requests, we do nothing until the
+        // data is definitely required.
+        if (isRequired()) {
+            loadRequired();
+        } else {
+            // We're using this field to check whether the pending request is optional or required.
+            resource.necessity = Resource::Optional;
+        }
+    }
+}
+
+template <typename T>
+void TileSource<T>::loadOptional() {
+    assert(!request);
+
+    resource.necessity = Resource::Optional;
+    request = fileSource.request(resource, [this](Response res) {
+        request.reset();
+
+        tileData.setTriedOptional();
+
+        if (res.error && res.error->reason == Response::Error::Reason::NotFound) {
+            // When the optional request could not be satisfied, don't treat it as an error.
+            // Instead, we make sure that the next request knows that there has been an optional
+            // request before by setting one of the prior* fields.
+            resource.priorExpires = Timestamp{ Seconds::zero() };
+        } else {
+            loadedData(res);
+        }
+
+        if (isRequired()) {
+            loadRequired();
+        }
+    });
+}
+
+template <typename T>
+void TileSource<T>::makeRequired() {
+    if (!request) {
+        loadRequired();
+    }
+}
+
+template <typename T>
+void TileSource<T>::makeOptional() {
+    if (resource.necessity == Resource::Required && request) {
+        // Abort a potential HTTP request.
+        request.reset();
+    }
+}
+
+template <typename T>
+void TileSource<T>::loadedData(const Response& res) {
+    if (res.error && res.error->reason != Response::Error::Reason::NotFound) {
+        tileData.setError(std::make_exception_ptr(std::runtime_error(res.error->message)));
+    } else if (res.notModified) {
+        resource.priorExpires = res.expires;
+        // Do not notify the TileData object; when we get this message, it already has the current
+        // version of the data.
+    } else {
+        resource.priorModified = res.modified;
+        resource.priorExpires = res.expires;
+        resource.priorEtag = res.etag;
+        tileData.setData(res.noContent ? nullptr : T::parseData(res.data), res.modified,
+                            res.expires);
+    }
+}
+
+template <typename T>
+void TileSource<T>::loadRequired() {
+    assert(!request);
+
+    resource.necessity = Resource::Required;
+    request = fileSource.request(resource, [this](Response res) { loadedData(res); });
+}
+
+} // namespace mbgl