Abstract_File.h

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#ifndef joedb_Abstract_File_declared
#define joedb_Abstract_File_declared
 
#include <stddef.h>
#include <stdint.h>
 
namespace joedb
{
 /// @ingroup journal
 class Abstract_File
 {
  public:
   /// Get the size of the file, or -1 if it is unknown
   virtual int64_t get_size() const {return -1;}
 
   /// Read a range of bytes
   ///
   /// The returned value may be less than size, even if the end of the file
   /// is not reached. 0 is returned if the end of the file is reached.
   virtual size_t pread(char *data, size_t size, int64_t offset) const {return 0;}
 
   /// Write a range of bytes. Extend file size if necessary.
   virtual void pwrite(const char *data, size_t size, int64_t offset) {}
 
   /// Write data and meta-data (such as file size) durably to permanent storage
   virtual void sync() {}
 
   /// Write data durably to permanent storage
   virtual void datasync() {sync();}
 
   /// Lock a range of bytes for reading (prevents writes, not reads)
   virtual void shared_lock(int64_t start, int64_t size) {}
 
   /// Lock a range of bytes for writing (prevents both writes and reads)
   virtual void exclusive_lock(int64_t start, int64_t size) {}
 
   /// Remove a lock. The range should match the range of a corresponding lock
   virtual void unlock(int64_t start, int64_t size) noexcept {}
 
   virtual ~Abstract_File() = default;
 };
}
 
#endif