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

    rb32c604 red903174  
    4141#define MAP_FAILED  ((void *) -1)
    43 #define MAP_SHARED       (1 << 0)
    44 #define MAP_PRIVATE      (1 << 1)
    45 #define MAP_FIXED        (1 << 2)
    46 #define MAP_ANONYMOUS    (1 << 3)
     43#define MAP_SHARED     (1 << 0)
     44#define MAP_PRIVATE    (1 << 1)
     45#define MAP_FIXED      (1 << 2)
     46#define MAP_ANONYMOUS  (1 << 3)
    4848#define PROTO_READ   AS_AREA_READ
    5050#define PROTO_EXEC   AS_AREA_EXEC
    52 extern void *mmap(void  *start, size_t length, int prot, int flags, int fd,
    53     off_t offset);
     52extern void *mmap(void *start, size_t length, int prot, int flags, int fd,
     53    aoff64_t offset);
    5454extern int munmap(void *start, size_t length);
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