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

Timestamp:

2010-02-10T23:51:23Z (15 years ago)

Author:

Martin Decky <martin@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

e70edd1

Parents:

b32c604f

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:

• uspace/lib/libc/generic/io/io.c (modified) (2 diffs)

uspace/lib/libc/generic/io/io.c

@@ -541 +541 @@
 }
 
-int fseek(FILE *stream, long offset, int origin)
-{
-        off_t rc = lseek(stream->fd, offset, origin);
-        if (rc == (off_t) (-1)) {
-                /* errno has been set by lseek. */
+int fseek(FILE *stream, off64_t offset, int whence)
+{
+        off64_t rc = lseek(stream->fd, offset, whence);
+        if (rc == (off64_t) (-1)) {
+                /* errno has been set by lseek64. */
                 return -1;
         }
@@ -554 +554 @@
 }
 
-int ftell(FILE *stream)
-{
-        off_t rc = lseek(stream->fd, 0, SEEK_CUR);
-        if (rc == (off_t) (-1)) {
-                /* errno has been set by lseek. */
-                return -1;
-        }
-
-        return rc;
+off64_t ftell(FILE *stream)
+{
+        return lseek(stream->fd, 0, SEEK_CUR);
 }