mrw-cxx/mrw/auto.hpp

#ifndef __MRW_AUTO_HPP__
#define __MRW_AUTO_HPP__

#include <sys/types.h> // size_t
#include <sys/mman.h> // PROT_READ, MAP_SHARED
#include <bfd.h> // bfd*

namespace mrw {

  /** @defgroup AutoTools Classes for Automated Resource Handling

      For pointers that have been allocated with @c new, you can use
      std::auto_ptr to automatically free them when you leave the
      context. Unfortunately there is no such thing for @c malloc
      (except @c malloca that only works for a subset of problems: if
      you and not a system call allocates memory), @c open and so on.
      These classes can take over the resource ownership.
  */
  //@{
  
  /** @brief Automatically closes a file when destructed.
      @pre #include <mrw/auto.hpp>

      AutoFile works exactly like std::auto_ptr, but not for files
      instead of pointers. Whenever the context of AutoFile is left,
      the opened file is close. This way, resources are freed even in
      case of exceptions.
  */
  class AutoFile {
    public:
      /// @brief Construct from an opened file.
      /// @note Don't close @c fd
      explicit AutoFile(int fd = -1) throw(): _fd(fd) {}
      /// @brief Takeover ownership from another AutoFile.
      AutoFile(AutoFile& o) throw(): _fd(o.release()) {}
      /// @brief Closes file if open.
      ~AutoFile() throw() {reset();}
      /// @brief Assign new file descriptor.
      /// The old file of @c this is closed if open.
      AutoFile& operator=(int fd) throw() {return reset(fd);}
      /// @brief Takeover ownership from another AutoFile.
      /// The old file of @c this is closed if open.
      AutoFile& operator=(AutoFile& other) throw() {
        return reset(other.release());
      }
      /// @brief get the file descriptor @return file descriptor
      operator const int() const throw() {
        return _fd;
      }
      /// @brief Give away ownership of the file. @return old file descriptor
      int release() throw() {
        int ret(_fd); _fd=-1;
        return ret;
      }
      /// @brief assign a new file descriptor
      /** The old file of @c this is closed if open. */
      AutoFile& reset(int = -1) throw();
    private:
      int _fd;                                    ///< the file descriptor
  };

  /** @brief Automatically call @c munmap for mmaped files on destruction.
      @pre #include <mrw/auto.hpp>
      
      It's the same as std::auto_ptr, but for @c mmap instead of @c
      new.  When the context of @c AutoMapper is left, @c munmap is
      called.
  */
  class AutoMapper {
    public:
      AutoMapper(void* cont = 0, size_t sz = 0) throw():
        _cont(cont), _sz(sz) {}
      AutoMapper(int, size_t=0, void* = 0,
                 int = PROT_READ, int = MAP_SHARED, off_t = 0) throw();
      ~AutoMapper() throw();
      operator const void*() const throw() {return _cont;}
      AutoMapper& set(void* cont, size_t sz) throw() {
        _cont=cont; _sz=sz;
        return *this;
      }
      void* release() throw() {
        void* ret(_cont); _cont=0; _sz=0;
        return ret;
      }
      const void* last() const throw() {
        return _cont && _sz ? (void*)((size_t)_cont+_sz-1) : 0;
      }
    private:
      void* _cont;
      size_t _sz;
  };

  /** @brief Automatically call @c bfd_close for @c bfd*.
      @pre #include <mrw/auto.hpp>
      
      It acts like a @c std::auto_ptr, but for @c bfd*, that means it
      calls @c bfd_close whenever the context is left.
  */
  class AutoBfd {
    public:
      AutoBfd(bfd* p=0) throw(): _bfd(p) {}
      ~AutoBfd() throw() {if (_bfd) bfd_close(_bfd);}
      AutoBfd& operator=(bfd* p) throw() {
        release(); _bfd=p; return *this;
      }
      AutoBfd& operator=(AutoBfd& o) throw() {
        release(); _bfd=o.release(); return *this;
      }
      operator bfd*() throw() {return _bfd;}
      bfd* operator->() throw() {return _bfd;}
      bfd* release() throw() {bfd* res(_bfd); _bfd = 0; return res;}
    private:
      bfd* _bfd;
  };

  /** @brief Automatically calls @c free for @c malloc allocated memory.
      @pre #include <mrw/auto.hpp>

      It works like a @c std::auto_ptr, but for memory that was
      allocated with @c malloc, not @c new. Memory is freed, whenever
      the context od @c AutoFree is left.
  */
  template <class T> class AutoFree {
    public:
      AutoFree(T* p=0) throw(): _p(p) {}
      AutoFree(AutoFree& o) throw(): _p(o.release()) {}
      ~AutoFree() throw() {if (_p) free(_p);}
      AutoFree& operator=(T* p) throw() {
        release(); _p=p; return *this;
      }
      AutoFree& operator=(AutoFree& o) throw() {
        release(); _p=o.release(); return *this;
      }
      operator T*() {return _p;}
      operator T**() {return &_p;}
      operator bool() {return _p;}
      T* release() throw() {T* r(_p); _p=0; return r;}
    private:
      T* _p;
  };
  //@}
}
#endif