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2010-02-10T23:51:23Z (13 years ago)
Martin Decky <martin@…>
lfn, master, serial

implement support for 64bit file offsets

  • the libc API is a small deviation from standard, but we have no reason to keep a strict backward compatibility with ancient code so far
    • the basic signed 64bit offset type is called off64_t
      • lseek() and fseek() take off64_t arguments (since the argument represents a relative offset)
      • ftell() returns off64_t values (since it is a wrapper of lseek())
      • vfs_seek() implementation supports negative offsets when SEEK_CUR and SEEK_END is used
    • aoff64_t is used for internal unsigned representation of sizes (in bytes, blocks, etc.) and absolute offsets
      • mmap() and ftruncate() take aoff64_t arguments (since the full range of the absolute file offset should be used here)
      • struct stat stores the file size as aoff64_t
    • in both cases the explicit range of the types shown in the names is helpful for proper filesystem and IPC interaction
    • note: size_t should be used only for representing in-memory sizes and offsets, not device and file-related information, and vice versa
      • the code base still needs a thorough revision with respect to this rule
    • PRIdOFF64 and PRIuOFF64 can be used for printing the offsets
  • VFS_OUT_LOOKUP returns the 64bit file size in two IPC arguments
    • since all 5 IPC arguments have already been taken, the fs_handle is returned as the return value (fs_handle has only 16 bits, thus the return value can be used for both indicating errors as negative values and returning positive handles)
  • VFS_OUT_READ and VFS_OUT_WRITE use aoff64_t absolute offsets split into two IPC arguments

replace bn_t with aoff64_t as a generic 64bit bytes/block counter type

note: filesystem drivers need to be revised with respect to make sure that all out-of-range checks are correct (especially w.r.t. file and block offsets)

1 edited


  • uspace/srv/bd/part/mbr_part/mbr_part.c

    rb32c604 red903174  
    9797        bool present;
    9898        /** Address of first block */
    99         bn_t start_addr;
     99        aoff64_t start_addr;
    100100        /** Number of blocks */
    101         bn_t length;
     101        aoff64_t length;
    102102        /** Device representing the partition (outbound device) */
    103103        dev_handle_t dev;
    249249                size_mb = (part->length * block_size + 1024 * 1024 - 1)
    250250                    / (1024 * 1024);
    251                 printf(NAME ": Registered device %s: %" PRIuBN " blocks "
     251                printf(NAME ": Registered device %s: %" PRIuOFF64 " blocks "
    252252                    "%" PRIu64 " MB.\n", name, part->length, size_mb);
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