struct bfd_iovec
................

Description

The struct bfd_iovec contains the internal file I/O class. Each BFD has an instance of this class and all file I/O is routed through it (it is assumed that the instance implements all methods listed below).

     struct bfd_iovec
     {
       /* To avoid problems with macros, a "b" rather than "f"
          prefix is prepended to each method name.  */
       /* Attempt to read/write NBYTES on ABFD's IOSTREAM storing/fetching
          bytes starting at PTR.  Return the number of bytes actually
          transfered (a read past end-of-file returns less than NBYTES),
          or -1 (setting bfd_error) if an error occurs.  */
       file_ptr (*bread) (struct bfd *abfd, void *ptr, file_ptr nbytes);
       file_ptr (*bwrite) (struct bfd *abfd, const void *ptr,
                           file_ptr nbytes);
       /* Return the current IOSTREAM file offset, or -1 (setting bfd_error
          if an error occurs.  */
       file_ptr (*btell) (struct bfd *abfd);
       /* For the following, on successful completion a value of 0 is returned.
          Otherwise, a value of -1 is returned (and  bfd_error is set).  */
       int (*bseek) (struct bfd *abfd, file_ptr offset, int whence);
       int (*bclose) (struct bfd *abfd);
       int (*bflush) (struct bfd *abfd);
       int (*bstat) (struct bfd *abfd, struct stat *sb);
       /* Mmap a part of the files. ADDR, LEN, PROT, FLAGS and OFFSET are the usual
          mmap parameter, except that LEN and OFFSET do not need to be page
          aligned.  Returns (void *)-1 on failure, mmapped address on success.
          Also write in MAP_ADDR the address of the page aligned buffer and in
          MAP_LEN the size mapped (a page multiple).  Use unmap with MAP_ADDR and
          MAP_LEN to unmap.  */
       void *(*bmmap) (struct bfd *abfd, void *addr, bfd_size_type len,
                       int prot, int flags, file_ptr offset,
                       void **map_addr, bfd_size_type *map_len);
     };
     extern const struct bfd_iovec _bfd_memory_iovec;

bfd_get_mtime
.............

Synopsis

     long bfd_get_mtime (bfd *abfd);

Description

Return the file modification time (as read from the file system, or from the archive header for archive members).

bfd_get_size
............

Synopsis

     file_ptr bfd_get_size (bfd *abfd);

Description

Return the file size (as read from file system) for the file associated with BFD ABFD.

The initial motivation for, and use of, this routine is not so we can get the exact size of the object the BFD applies to, since that might not be generally possible (archive members for example). It would be ideal if someone could eventually modify it so that such results were guaranteed.

Instead, we want to ask questions like "is this NNN byte sized object I'm about to try read from file offset YYY reasonable?" As as example of where we might do this, some object formats use string tables for which the first sizeof (long) bytes of the table contain the size of the table itself, including the size bytes. If an application tries to read what it thinks is one of these string tables, without some way to validate the size, and for some reason the size is wrong (byte swapping error, wrong location for the string table, etc.), the only clue is likely to be a read error when it tries to read the table, or a "virtual memory exhausted" error when it tries to allocate 15 bazillon bytes of space for the 15 bazillon byte table it is about to read. This function at least allows us to answer the question, "is the size reasonable?".

bfd_mmap
........

Synopsis

     void *bfd_mmap (bfd *abfd, void *addr, bfd_size_type len,
         int prot, int flags, file_ptr offset,
         void **map_addr, bfd_size_type *map_len);

Description

Return mmap()ed region of the file, if possible and implemented. LEN and OFFSET do not need to be page aligned.  The page aligned address and length are written to MAP_ADDR and MAP_LEN.