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Changeset ed903174 in mainline for uspace/lib/libc/generic/io/io.c


Ignore:
Timestamp:
2010-02-10T23:51:23Z (12 years ago)
Author:
Martin Decky <martin@…>
Branches:
lfn, master
Children:
e70edd1
Parents:
b32c604
Message:

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)

File:
1 edited

Legend:

Unmodified
Added
Removed
  • uspace/lib/libc/generic/io/io.c

    rb32c604 red903174  
    541541}
    542542
    543 int fseek(FILE *stream, long offset, int origin)
    544 {
    545         off_t rc = lseek(stream->fd, offset, origin);
    546         if (rc == (off_t) (-1)) {
    547                 /* errno has been set by lseek. */
     543int fseek(FILE *stream, off64_t offset, int whence)
     544{
     545        off64_t rc = lseek(stream->fd, offset, whence);
     546        if (rc == (off64_t) (-1)) {
     547                /* errno has been set by lseek64. */
    548548                return -1;
    549549        }
     
    554554}
    555555
    556 int ftell(FILE *stream)
    557 {
    558         off_t rc = lseek(stream->fd, 0, SEEK_CUR);
    559         if (rc == (off_t) (-1)) {
    560                 /* errno has been set by lseek. */
    561                 return -1;
    562         }
    563 
    564         return rc;
     556off64_t ftell(FILE *stream)
     557{
     558        return lseek(stream->fd, 0, SEEK_CUR);
    565559}
    566560
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