[ECOS] readwrite function in libc

[ECOS] readwrite function in libc

[james chen]

Hi,

    in the function of readwrite ( io\fileio\current\src\io.cxx)
{
     ...
    LOCK_FILE( fp );
    ret = op( fp, &uio );
    UNLOCK_FILE( fp );
    cnt -= uio.uio_resid;
    cyg_fp_free( fp );
    CYG_CANCELLATION_POINT;
    FILEIO_RETURN_VALUE(cnt);
}
if ret is not equal ENOERR, this may not compatible with read() standard. Is
there a bug in it:-)

Best Regards,
james

----------------------------------------------------------------------------
--------------------------
read - read from a file descriptor
#include <unistd.h>

ssize_t read(int fd, void *buf, size_t count );

DESCRIPTION
 read() attempts to read up to count bytes from file descriptor fd
into the buffer starting at buf. If count is zero, read()returns zero
and has no other results. If count is greater than SSIZE_MAX, the
result is unspecified.

RETURN VALUE
 On success, the number of bytes read is returned (zero indicates end of
file), and the file position is advanced by this number.
It is not an error if this number is smaller than the number of bytes
requested; this may happen for example because fewer bytes are actually
available right now (maybe because we were close to end-of-file, or
because we are reading from a pipe, or from a terminal), or because
read()was interrupted by a signal. On error, -1 is returned, and
errno is set appropriately. In this case it is left unspecified whether
the file position (if any) changes.

ERRORS

 EINTR
  The call was interrupted by a signal before any data was read.

 EAGAIN
  Non-blocking I/O has been selected using

 O_NONBLOCK
  and no data was immediately available for reading.

 EIO
  I/O error. This will happen for example when the process is in a
  background process group, tries to read from its controlling tty,
  and either it is ignoring or blocking SIGTTIN or its process group
  is orphaned.  It may also occur when there is a low-level I/O error
  while reading from a disk or tape.

 EISDIR
  fd refers to a directory.
 EBADF
  fd is not a valid file descriptor or is not open for reading.

 EINVAL
  fd is attached to an object which is unsuitable for reading.

 EFAULT
  buf is outside your accessible address space. Other errors may
  occur, depending on the object connected to fd. POSIX allows a
  read that is interrupted after reading some data to return -1
  (with errno set to EINTR) or to return the number of bytes
  already read.

Re: [ECOS] readwrite function in libc

[Jonathan Larmour]

james chen wrote:
> 
> Hi,
> 
>     in the function of readwrite ( io\fileio\current\src\io.cxx)
> {
>      ...
>     LOCK_FILE( fp );
>     ret = op( fp, &uio );
>     UNLOCK_FILE( fp );
>     cnt -= uio.uio_resid;
>     cyg_fp_free( fp );
>     CYG_CANCELLATION_POINT;
>     FILEIO_RETURN_VALUE(cnt);
> }
> if ret is not equal ENOERR, this may not compatible with read() standard. Is
> there a bug in it:-)

I don't believe so given the definition of FILEIO_RETURN_VALUE, so it's up
to you to tell us where you think there is a bug and why.

Jifl
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