OpenSpace/include/openspace/engine/downloadmanager.h

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 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2016                                                               *
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#ifndef __DOWNLOADMANAGER_H__
#define __DOWNLOADMANAGER_H__

#include <ghoul/filesystem/file.h>
#include <ghoul/filesystem/directory.h>

#include <functional>
#include <memory>
#include <string>
#include <vector>
#include <future>

namespace openspace {

// Multithreaded
class DownloadManager {
public:
    struct FileFuture {
        // Since the FileFuture object will be used from multiple threads, we have to be
        // careful about the access pattern, that is, no values should be read and written
        // by both the DownloadManager and the outside threads.
        FileFuture(std::string file);

        // Values that are written by the DownloadManager to be consumed by others
        long long currentSize;
        long long totalSize;
        float progress; // [0,1]
        float secondsRemaining;
        bool isFinished;
        bool isAborted;
        std::string filePath;
        std::string errorMessage;
        std::string format;
        // Values set by others to be consumed by the DownloadManager
        bool abortDownload;
    };

    struct MemoryFile {
        char* buffer;
        size_t size;
        std::string format;
        bool corrupted;
    };

    using DownloadProgressCallback = std::function<void(const FileFuture&)>;
    using DownloadFinishedCallback = std::function<void(const FileFuture&)>;

    using SuccessCallback = std::function<void(const MemoryFile&)>;
    using ErrorCallback = std::function<void(const std::string&)>;

    using RequestFinishedCallback = std::function<void(std::string)>;
    using AsyncDownloadFinishedCallback =
        std::function<void(const std::vector<std::shared_ptr<FileFuture>>&)>;

    //Just a helper function to check if a future is ready to ".get()". Not specific
    // to DownloadManager but is useful for anyone using the DownloadManager
    template<typename R>
    static bool futureReady(std::future<R> const& f)
    { return f.wait_for(std::chrono::seconds(0)) == std::future_status::ready; }

    DownloadManager(std::string requestURL, int applicationVersion,
        bool useMultithreadedDownload = true);

    // callbacks happen on a different thread
    std::shared_ptr<FileFuture> downloadFile(const std::string& url, const ghoul::filesystem::File& file,
        bool overrideFile = true,
        DownloadFinishedCallback finishedCallback = DownloadFinishedCallback(),
        DownloadProgressCallback progressCallback = DownloadProgressCallback()
    );

    std::future<MemoryFile> fetchFile(
    const std::string& url,
    SuccessCallback successCallback = SuccessCallback(), ErrorCallback errorCallback = ErrorCallback());

    std::vector<std::shared_ptr<FileFuture>> downloadRequestFiles(const std::string& identifier,
        const ghoul::filesystem::Directory& destination, int version,
        bool overrideFiles = true,
        DownloadFinishedCallback finishedCallback = DownloadFinishedCallback(),
        DownloadProgressCallback progressCallback = DownloadProgressCallback()
    );

    void downloadRequestFilesAsync(const std::string& identifier,
        const ghoul::filesystem::Directory& destination, int version,
        bool overrideFiles, AsyncDownloadFinishedCallback callback
    );

    void getFileExtension(const std::string& url,
        RequestFinishedCallback finishedCallback = RequestFinishedCallback());

private:
    std::vector<std::string> _requestURL;
    int _applicationVersion;
    bool _useMultithreadedDownload;
};

} // namespace openspace

#endif // __DOWNLOADMANAGER_H__