95 lines
2.0 KiB
C++
95 lines
2.0 KiB
C++
#ifndef VOXEL_FILE_LOCKER_H
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#define VOXEL_FILE_LOCKER_H
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#include <core/hash_map.h>
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#include <core/os/file_access.h>
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#include <core/os/mutex.h>
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#include <core/os/rw_lock.h>
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// Performs software locking on paths,
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// so that multiple threads (controlled by this module) wanting to access the same file will lock a shared mutex.
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// Note: has nothing to do with voxels, it's just prefixed.
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class VoxelFileLocker {
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public:
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~VoxelFileLocker() {
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const String *key = nullptr;
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while ((key = _files.next(key))) {
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File *f = _files[*key];
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memdelete(f);
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}
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}
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void lock_read(String fpath) {
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lock(fpath, true);
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}
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void lock_write(String fpath) {
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lock(fpath, false);
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}
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void unlock(String fpath) {
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unlock_internal(fpath);
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}
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private:
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struct File {
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RWLock lock;
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bool read_only;
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};
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void lock(String fpath, bool read_only) {
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File *fp = nullptr;
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{
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MutexLock lock(_files_mutex);
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File **fpp = _files.getptr(fpath);
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if (fpp == nullptr) {
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fp = memnew(File);
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_files.set(fpath, fp);
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}
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else {
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fp = *fpp;
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}
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}
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if (read_only) {
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fp->lock.read_lock();
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// The read lock was acquired. It means nobody is writing.
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fp->read_only = true;
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} else {
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fp->lock.write_lock();
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// The write lock was acquired. It means only one thread is writing.
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fp->read_only = false;
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}
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}
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void unlock_internal(String fpath) {
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File *fp = nullptr;
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// I assume `get_path` returns the same string that was used to open it
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{
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MutexLock lock(_files_mutex);
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File **fpp = _files.getptr(fpath);
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if (fpp != nullptr) {
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fp = *fpp;
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}
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}
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ERR_FAIL_COND(fp == nullptr);
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// TODO FileAccess::reopen can have been called, nullifying my efforts to enforce thread sync :|
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// So for now please don't do that
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if (fp->read_only) {
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fp->lock.read_unlock();
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} else {
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fp->lock.write_unlock();
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}
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}
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private:
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Mutex _files_mutex;
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// Had to use dynamic allocs because HashMap does not implement move semantics
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HashMap<String, File *> _files;
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};
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#endif // VOXEL_FILE_LOCKER_H
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