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Adds OS internal function nx_write() which is functionally equivalent to write() except that it does not set the errno variable and do not cause cancellation points.

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This commit is contained in:
Gregory Nutt
2017-10-11 10:18:30 -06:00
parent af072d52bc
commit a00d8e16a1
14 changed files with 212 additions and 128 deletions
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fs/vfs/fs_write.c
+105 -67
View File
@@ -65,8 +65,24 @@
*
* Description:
* Equivalent to the standard write() function except that is accepts a
* struct file instance instead of a file descriptor. Currently used
* only by aio_write();
* struct file instance instead of a file descriptor. It is functionally
* equivalent to write() except that in addition to the differences in
* input paramters:
*
* - It does not modify the errno variable,
* - It is not a cancellation point, and
* - It does not handle socket descriptors.
*
* Input Parameters:
* filep - Instance of struct file to use with the write
* buf - Data to write
* nbytes - Length of data to write
*
* Returned Value:
* On success, the number of bytes written are returned (zero indicates
* nothing was written). On any failure, a negated errno value is returned
* (see comments withwrite() for a description of the appropriate errno
* values).
*
****************************************************************************/
@@ -94,6 +110,81 @@ ssize_t file_write(FAR struct file *filep, FAR const void *buf, size_t nbytes)
return inode->u.i_ops->write(filep, buf, nbytes);
}
/****************************************************************************
* Name: nx_write
*
* Description:
* nx_write() writes up to nytes bytes to the file referenced by the file
* descriptor fd from the buffer starting at buf. nx_write() is an
* internal OS function. It is functionally equivalent to write() except
* that:
*
* - It does not modify the errno variable, and
* - It is not a cancellation point.
*
* Input Parameters:
* fd - file descriptor (or socket descriptor) to write to
* buf - Data to write
* nbytes - Length of data to write
*
* Returned Value:
* On success, the number of bytes written are returned (zero indicates
* nothing was written). On any failure, a negated errno value is returned
* (see comments withwrite() for a description of the appropriate errno
* values).
*
****************************************************************************/
ssize_t nx_write(int fd, FAR const void *buf, size_t nbytes)
{
#if CONFIG_NFILE_DESCRIPTORS > 0
FAR struct file *filep;
#endif
ssize_t ret;
if (buf == NULL)
{
return -EINVAL;
}
/* Did we get a valid file descriptor? */
#if CONFIG_NFILE_DESCRIPTORS > 0
if ((unsigned int)fd >= CONFIG_NFILE_DESCRIPTORS)
#endif
{
#if defined(CONFIG_NET_TCP) && CONFIG_NSOCKET_DESCRIPTORS > 0
/* Write to a socket descriptor is equivalent to send with flags == 0. */
ret = nx_send(fd, buf, nbytes, 0);
#else
ret = -EBADF;
#endif
}
#if CONFIG_NFILE_DESCRIPTORS > 0
else
{
/* The descriptor is in the right range to be a file descriptor..
* write to the file. Note that fs_getfilep() will set the errno on
* failure.
*/
ret = (ssize_t)fs_getfilep(fd, &filep);
if (ret >= 0)
{
/* Perform the write operation using the file descriptor as an
* index. Note that file_write() will set the errno on failure.
*/
ret = file_write(filep, buf, nbytes);
}
}
#endif
return ret;
}
/****************************************************************************
* Name: write
*
@@ -101,13 +192,13 @@ ssize_t file_write(FAR struct file *filep, FAR const void *buf, size_t nbytes)
* write() writes up to nytes bytes to the file referenced by the file
* descriptor fd from the buffer starting at buf.
*
* Parameters:
* fd file descriptor (or socket descriptor) to write to
* buf Data to write
* nbytes Length of data to write
* Input Parameters:
* fd - file descriptor (or socket descriptor) to write to
* buf - Data to write
* nbytes - Length of data to write
*
* Returned Value:
* On success, the number of bytes written are returned (zero indicates
* On success, the number of bytes written are returned (zero indicates
* nothing was written). On error, -1 is returned, and errno is set appro-
* priately:
*
@@ -140,78 +231,25 @@ ssize_t file_write(FAR struct file *filep, FAR const void *buf, size_t nbytes)
* signal. (Thus, the write return value is seen only if the program
* catches, blocks or ignores this signal.)
*
* Assumptions:
*
********************************************************************************************/
****************************************************************************/
ssize_t write(int fd, FAR const void *buf, size_t nbytes)
{
#if CONFIG_NFILE_DESCRIPTORS > 0
FAR struct file *filep;
#endif
ssize_t ret;
/* write() is a cancellation point */
(void)enter_cancellation_point();
if (buf == NULL)
/* Let nx_write() do all of the work */
ret = nx_write(fd, buf, nbytes);
if (ret < 0)
{
ret = -EINVAL;
goto errout;
set_errno(ret);
ret = ERROR;
}
/* Did we get a valid file descriptor? */
#if CONFIG_NFILE_DESCRIPTORS > 0
if ((unsigned int)fd >= CONFIG_NFILE_DESCRIPTORS)
#endif
{
#if defined(CONFIG_NET_TCP) && CONFIG_NSOCKET_DESCRIPTORS > 0
/* Write to a socket descriptor is equivalent to send with flags == 0. */
ret = nx_send(fd, buf, nbytes, 0);
if (ret < 0)
{
goto errout;
}
#else
ret = -EBADF;
goto errout;
#endif
}
#if CONFIG_NFILE_DESCRIPTORS > 0
else
{
/* The descriptor is in the right range to be a file descriptor..
* write to the file. Note that fs_getfilep() will set the errno on
* failure.
*/
ret = (ssize_t)fs_getfilep(fd, &filep);
if (ret < 0)
{
goto errout;
}
/* Perform the write operation using the file descriptor as an
* index. Note that file_write() will set the errno on failure.
*/
ret = file_write(filep, buf, nbytes);
if (ret < 0)
{
goto errout;
}
}
#endif
leave_cancellation_point();
return ret;
errout:
set_errno(-ret);
leave_cancellation_point();
return ERROR;
}