dir_watch.h

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/* Copyright (C) 2022 Wildfire Games.
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 * The above copyright notice and this permission notice shall be included
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 */

/*
 * portable directory change notification API.
 */

#ifndef INCLUDED_DIR_WATCH
#define INCLUDED_DIR_WATCH

#include "lib/os_path.h"

#include <vector>
#include <memory>

struct DirWatch;
typedef std::shared_ptr<DirWatch> PDirWatch;

/**
 * start watching a single directory for changes.
 *
 * @param path (must end in slash)
 * @param dirWatch opaque smart pointer to the watch state; used to
 * manage its lifetime (this is deemed more convenient than a
 * separate dir_watch_Remove interface).
 *
 * clients typically want to watch entire directory subtrees (e.g. a mod),
 * which is supported by Windows but not FAM. to reduce overhead, the
 * Windows backend always watches subtrees, but portable clients should
 * still add a watch for each subdirectory (the shared watch state is
 * reference-counted).
 * rationale: since the VFS has per-directory data structures, it is
 * convenient to store PDirWatch there instead of creating a second
 * tree structure here.
 **/
Status dir_watch_Add(const OsPath& path, PDirWatch& dirWatch);

class DirWatchNotification
{
public:
    enum EType
    {
        Created,
        Deleted,
        Changed
    };

    DirWatchNotification(const OsPath& pathname, EType type)
        : pathname(pathname), type(type)
    {
    }

    const OsPath& Pathname() const
    {
        return pathname;
    }

    EType Type() const
    {
        return type;
    }

private:
    OsPath pathname;
    EType type;
};

typedef std::vector<DirWatchNotification> DirWatchNotifications;

/**
 * return all pending directory watch notifications.
 *
 * @param notifications receives any pending notifications in unspecified order.
 * @return Status (INFO::OK doesn't imply notifications were returned)
 *
 * note: the run time of this function is independent of the number of
 * directory watches and number of files.
 *
 * rationale for a polling interface: users (e.g. the main game loop)
 * typically want to receive change notifications at a single point,
 * rather than deal with the complexity of asynchronous notifications.
 **/
Status dir_watch_Poll(DirWatchNotifications& notifications);

#endif  // #ifndef INCLUDED_DIR_WATCH