File_Slice.h

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#ifndef joedb_File_Slice_declared
#define joedb_File_Slice_declared
 
#include "joedb/journal/Readonly_Memory_File.h"
#include "joedb/journal/Posix_File.h"
 
#include <sys/mman.h>
 
namespace joedb
{
 /// @ingroup journal
 class File_Slice: public Readonly_Memory_File
 {
  private:
   const size_t mapped_size;
 
  public:
   File_Slice(int fd, size_t offset, size_t size):
    Readonly_Memory_File
    (
     (char *)mmap
     (
      nullptr,
      offset + size,
      PROT_READ,
      MAP_PRIVATE,
      fd,
      0
     ) + offset,
     size
    ),
    mapped_size(offset + size)
   {
    if (data - offset == MAP_FAILED)
     Posix_File::throw_last_error("mapping", "file");
   }
 
   File_Slice(const File_Slice &) = delete;
   File_Slice &operator=(const File_Slice &) = delete;
 
   ~File_Slice()
   {
    munmap(const_cast<void *>(static_cast<const void *>(data)), mapped_size);
   }
 }; 
}
 
#endif