bfdio.texi revision 1.1.1.2
1@findex struct bfd_iovec 2@subsubsection @code{struct bfd_iovec} 3@strong{Description}@* 4The @code{struct bfd_iovec} contains the internal file I/O class. 5Each @code{BFD} has an instance of this class and all file I/O is 6routed through it (it is assumed that the instance implements 7all methods listed below). 8@example 9struct bfd_iovec 10@{ 11 /* To avoid problems with macros, a "b" rather than "f" 12 prefix is prepended to each method name. */ 13 /* Attempt to read/write NBYTES on ABFD's IOSTREAM storing/fetching 14 bytes starting at PTR. Return the number of bytes actually 15 transfered (a read past end-of-file returns less than NBYTES), 16 or -1 (setting @code{bfd_error}) if an error occurs. */ 17 file_ptr (*bread) (struct bfd *abfd, void *ptr, file_ptr nbytes); 18 file_ptr (*bwrite) (struct bfd *abfd, const void *ptr, 19 file_ptr nbytes); 20 /* Return the current IOSTREAM file offset, or -1 (setting @code{bfd_error} 21 if an error occurs. */ 22 file_ptr (*btell) (struct bfd *abfd); 23 /* For the following, on successful completion a value of 0 is returned. 24 Otherwise, a value of -1 is returned (and @code{bfd_error} is set). */ 25 int (*bseek) (struct bfd *abfd, file_ptr offset, int whence); 26 int (*bclose) (struct bfd *abfd); 27 int (*bflush) (struct bfd *abfd); 28 int (*bstat) (struct bfd *abfd, struct stat *sb); 29 /* Just like mmap: (void*)-1 on failure, mmapped address on success. */ 30 void *(*bmmap) (struct bfd *abfd, void *addr, bfd_size_type len, 31 int prot, int flags, file_ptr offset); 32@}; 33extern const struct bfd_iovec _bfd_memory_iovec; 34@end example 35 36@findex bfd_get_mtime 37@subsubsection @code{bfd_get_mtime} 38@strong{Synopsis} 39@example 40long bfd_get_mtime (bfd *abfd); 41@end example 42@strong{Description}@* 43Return the file modification time (as read from the file system, or 44from the archive header for archive members). 45 46@findex bfd_get_size 47@subsubsection @code{bfd_get_size} 48@strong{Synopsis} 49@example 50file_ptr bfd_get_size (bfd *abfd); 51@end example 52@strong{Description}@* 53Return the file size (as read from file system) for the file 54associated with BFD @var{abfd}. 55 56The initial motivation for, and use of, this routine is not 57so we can get the exact size of the object the BFD applies to, since 58that might not be generally possible (archive members for example). 59It would be ideal if someone could eventually modify 60it so that such results were guaranteed. 61 62Instead, we want to ask questions like "is this NNN byte sized 63object I'm about to try read from file offset YYY reasonable?" 64As as example of where we might do this, some object formats 65use string tables for which the first @code{sizeof (long)} bytes of the 66table contain the size of the table itself, including the size bytes. 67If an application tries to read what it thinks is one of these 68string tables, without some way to validate the size, and for 69some reason the size is wrong (byte swapping error, wrong location 70for the string table, etc.), the only clue is likely to be a read 71error when it tries to read the table, or a "virtual memory 72exhausted" error when it tries to allocate 15 bazillon bytes 73of space for the 15 bazillon byte table it is about to read. 74This function at least allows us to answer the question, "is the 75size reasonable?". 76 77@findex bfd_mmap 78@subsubsection @code{bfd_mmap} 79@strong{Synopsis} 80@example 81void *bfd_mmap (bfd *abfd, void *addr, bfd_size_type len, 82 int prot, int flags, file_ptr offset); 83@end example 84@strong{Description}@* 85Return mmap()ed region of the file, if possible and implemented. 86 87