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Changeset ed903174 in mainline for uspace/lib/libc/include/stdio.h

2010-02-10T23:51:23Z (12 years ago)
Martin Decky <martin@…>
lfn, master

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/lib/libc/include/stdio.h

    rb32c604 red903174  
    4646#define BUFSIZ  4096
    48 #define DEBUG(fmt, ...) \
     48#define DEBUG(fmt, ...)se\
    4949        { \
    5050                char _buf[256]; \
    5656#ifndef SEEK_SET
    5757        #define SEEK_SET  0
     60#ifndef SEEK_CUR
    5861        #define SEEK_CUR  1
     64#ifndef SEEK_END
    5965        #define SEEK_END  2
    135141extern size_t fwrite(const void *, size_t, size_t, FILE *);
    137 extern int fseek(FILE *, long, int);
     143extern int fseek(FILE *, off64_t, int);
    138144extern void rewind(FILE *);
    139 extern int ftell(FILE *);
     145extern off64_t ftell(FILE *);
    140146extern int feof(FILE *);
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