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#pragma once
#include <mbgl/renderer/tile_parameters.hpp>
#include <mbgl/storage/file_source.hpp>
#include <mbgl/tile/tile_loader.hpp>
#include <mbgl/util/async_request.hpp>
#include <mbgl/util/tileset.hpp>
#include <cassert>
namespace {
inline std::exception_ptr getCantLoadTileError() {
return std::make_exception_ptr(std::runtime_error("Can't load tile."));
}
} // namespace
namespace mbgl {
template <typename T>
TileLoader<T>::TileLoader(T& tile_,
const OverscaledTileID& id,
const TileParameters& parameters,
const Tileset& tileset)
: tile(tile_),
necessity(TileNecessity::Optional),
resource(Resource::tile(
tileset.tiles.at(0),
parameters.pixelRatio,
id.canonical.x,
id.canonical.y,
id.canonical.z,
tileset.scheme,
Resource::LoadingMethod::CacheOnly)),
fileSource(parameters.fileSource) {
assert(!request);
if (!fileSource) {
tile.setError(getCantLoadTileError());
return;
}
if (fileSource->supportsCacheOnlyRequests()) {
// When supported, the first request is always optional, even if the TileLoader
// is marked as required. That way, we can let the first optional request continue
// to load when the TileLoader 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.
loadFromCache();
} else if (necessity == TileNecessity::Required) {
// When the file source doesn't support cache-only requests, and we definiitely need this
// data, we can start out with a network request immediately.
loadFromNetwork();
} else {
// When the FileSource doesn't support cache-only requests, we do nothing until the
// data is definitely required.
}
}
template <typename T>
TileLoader<T>::~TileLoader() = default;
template <typename T>
void TileLoader<T>::loadFromCache() {
assert(!request);
if (!fileSource) {
tile.setError(getCantLoadTileError());
return;
}
resource.loadingMethod = Resource::LoadingMethod::CacheOnly;
request = fileSource->request(resource, [this](Response res) {
request.reset();
tile.setTriedCache();
if (res.error && res.error->reason == Response::Error::Reason::NotFound) {
// When the cache-only request could not be satisfied, don't treat it as an error.
// A cache lookup could still return data, _and_ an error, in particular when we were
// able to find the data, but it is expired and the Cache-Control headers indicated that
// we aren't allowed to use expired responses. In this case, we still get the data which
// we can use in our conditional network request.
resource.priorModified = res.modified;
resource.priorExpires = res.expires;
resource.priorEtag = res.etag;
resource.priorData = res.data;
} else {
loadedData(res);
}
if (necessity == TileNecessity::Required) {
loadFromNetwork();
}
});
}
template <typename T>
void TileLoader<T>::makeRequired() {
if (!request) {
loadFromNetwork();
}
}
template <typename T>
void TileLoader<T>::makeOptional() {
if (resource.loadingMethod == Resource::LoadingMethod::NetworkOnly && request) {
// Abort the current request, but only when we know that we're specifically querying for a
// network resource only.
request.reset();
}
}
template <typename T>
void TileLoader<T>::loadedData(const Response& res) {
if (res.error && res.error->reason != Response::Error::Reason::NotFound) {
tile.setError(std::make_exception_ptr(std::runtime_error(res.error->message)));
} else if (res.notModified) {
resource.priorExpires = res.expires;
// Do not notify the tile; when we get this message, it already has the current
// version of the data.
tile.setMetadata(res.modified, res.expires);
} else {
resource.priorModified = res.modified;
resource.priorExpires = res.expires;
resource.priorEtag = res.etag;
tile.setMetadata(res.modified, res.expires);
tile.setData(res.noContent ? nullptr : res.data);
}
}
template <typename T>
void TileLoader<T>::loadFromNetwork() {
assert(!request);
if (!fileSource) {
tile.setError(getCantLoadTileError());
return;
}
// Instead of using Resource::LoadingMethod::All, we're first doing a CacheOnly, and then a
// NetworkOnly request.
resource.loadingMethod = Resource::LoadingMethod::NetworkOnly;
request = fileSource->request(resource, [this](Response res) { loadedData(res); });
}
} // namespace mbgl
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