seaweedfs/weed/mount/weedfs_file_io.go

package mount

import (
	"github.com/hanwen/go-fuse/v2/fuse"
)

/**
 * Read data
 *
 * Read should send exactly the number of bytes requested except
 * on EOF or error, otherwise the rest of the data will be
 * substituted with zeroes.  An exception to this is when the file
 * has been opened in 'direct_io' mode, in which case the return
 * value of the read system call will reflect the return value of
 * this operation.
 *
 * fi->fh will contain the value set by the open method, or will
 * be undefined if the open method didn't set any value.
 *
 * Valid replies:
 *   fuse_reply_buf
 *   fuse_reply_iov
 *   fuse_reply_data
 *   fuse_reply_err
 *
 * @param req request handle
 * @param ino the inode number
 * @param size number of bytes to read
 * @param off offset to read from
 * @param fi file information
 */
func (wfs *WFS) Read(cancel <-chan struct{}, in *fuse.ReadIn, buf []byte) (fuse.ReadResult, fuse.Status) {
	return nil, fuse.ENOSYS
}

/**
 * Write data
 *
 * Write should return exactly the number of bytes requested
 * except on error.  An exception to this is when the file has
 * been opened in 'direct_io' mode, in which case the return value
 * of the write system call will reflect the return value of this
 * operation.
 *
 * Unless FUSE_CAP_HANDLE_KILLPRIV is disabled, this method is
 * expected to reset the setuid and setgid bits.
 *
 * fi->fh will contain the value set by the open method, or will
 * be undefined if the open method didn't set any value.
 *
 * Valid replies:
 *   fuse_reply_write
 *   fuse_reply_err
 *
 * @param req request handle
 * @param ino the inode number
 * @param buf data to write
 * @param size number of bytes to write
 * @param off offset to write to
 * @param fi file information
 */
func (wfs *WFS) Write(cancel <-chan struct{}, in *fuse.WriteIn, data []byte) (written uint32, code fuse.Status) {
	return 0, fuse.ENOSYS
}

/**
	 * Open a file
	 *
	 * Open flags are available in fi->flags. The following rules
	 * apply.
	 *
	 *  - Creation (O_CREAT, O_EXCL, O_NOCTTY) flags will be
	 *    filtered out / handled by the kernel.
	 *
	 *  - Access modes (O_RDONLY, O_WRONLY, O_RDWR) should be used
	 *    by the filesystem to check if the operation is
	 *    permitted.  If the ``-o default_permissions`` mount
	 *    option is given, this check is already done by the
	 *    kernel before calling open() and may thus be omitted by
	 *    the filesystem.
	 *
	 *  - When writeback caching is enabled, the kernel may send
	 *    read requests even for files opened with O_WRONLY. The
	 *    filesystem should be prepared to handle this.
	 *
	 *  - When writeback caching is disabled, the filesystem is
	 *    expected to properly handle the O_APPEND flag and ensure
	 *    that each write is appending to the end of the file.
	 *
         *  - When writeback caching is enabled, the kernel will
	 *    handle O_APPEND. However, unless all changes to the file
	 *    come through the kernel this will not work reliably. The
	 *    filesystem should thus either ignore the O_APPEND flag
	 *    (and let the kernel handle it), or return an error
	 *    (indicating that reliably O_APPEND is not available).
	 *
	 * Filesystem may store an arbitrary file handle (pointer,
	 * index, etc) in fi->fh, and use this in other all other file
	 * operations (read, write, flush, release, fsync).
	 *
	 * Filesystem may also implement stateless file I/O and not store
	 * anything in fi->fh.
	 *
	 * There are also some flags (direct_io, keep_cache) which the
	 * filesystem may set in fi, to change the way the file is opened.
	 * See fuse_file_info structure in <fuse_common.h> for more details.
	 *
	 * If this request is answered with an error code of ENOSYS
	 * and FUSE_CAP_NO_OPEN_SUPPORT is set in
	 * `fuse_conn_info.capable`, this is treated as success and
	 * future calls to open and release will also succeed without being
	 * sent to the filesystem process.
	 *
	 * Valid replies:
	 *   fuse_reply_open
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param fi file information
*/
func (wfs *WFS) Open(cancel <-chan struct{}, in *fuse.OpenIn, out *fuse.OpenOut) (status fuse.Status) {
	return fuse.ENOSYS
}

/**
 * Flush method
 *
 * This is called on each close() of the opened file.
 *
 * Since file descriptors can be duplicated (dup, dup2, fork), for
 * one open call there may be many flush calls.
 *
 * Filesystems shouldn't assume that flush will always be called
 * after some writes, or that if will be called at all.
 *
 * fi->fh will contain the value set by the open method, or will
 * be undefined if the open method didn't set any value.
 *
 * NOTE: the name of the method is misleading, since (unlike
 * fsync) the filesystem is not forced to flush pending writes.
 * One reason to flush data is if the filesystem wants to return
 * write errors during close.  However, such use is non-portable
 * because POSIX does not require [close] to wait for delayed I/O to
 * complete.
 *
 * If the filesystem supports file locking operations (setlk,
 * getlk) it should remove all locks belonging to 'fi->owner'.
 *
 * If this request is answered with an error code of ENOSYS,
 * this is treated as success and future calls to flush() will
 * succeed automatically without being send to the filesystem
 * process.
 *
 * Valid replies:
 *   fuse_reply_err
 *
 * @param req request handle
 * @param ino the inode number
 * @param fi file information
 *
 * [close]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/close.html
 */
func (wfs *WFS) Flush(cancel <-chan struct{}, in *fuse.FlushIn) fuse.Status {
	return fuse.ENOSYS
}

/**
 * Release an open file
 *
 * Release is called when there are no more references to an open
 * file: all file descriptors are closed and all memory mappings
 * are unmapped.
 *
 * For every open call there will be exactly one release call (unless
 * the filesystem is force-unmounted).
 *
 * The filesystem may reply with an error, but error values are
 * not returned to close() or munmap() which triggered the
 * release.
 *
 * fi->fh will contain the value set by the open method, or will
 * be undefined if the open method didn't set any value.
 * fi->flags will contain the same flags as for open.
 *
 * Valid replies:
 *   fuse_reply_err
 *
 * @param req request handle
 * @param ino the inode number
 * @param fi file information
 */
func (wfs *WFS) Release(cancel <-chan struct{}, in *fuse.ReleaseIn) {
}

/**
 * Synchronize file contents
 *
 * If the datasync parameter is non-zero, then only the user data
 * should be flushed, not the meta data.
 *
 * If this request is answered with an error code of ENOSYS,
 * this is treated as success and future calls to fsync() will
 * succeed automatically without being send to the filesystem
 * process.
 *
 * Valid replies:
 *   fuse_reply_err
 *
 * @param req request handle
 * @param ino the inode number
 * @param datasync flag indicating if only data should be flushed
 * @param fi file information
 */
func (wfs *WFS) Fsync(cancel <-chan struct{}, in *fuse.FsyncIn) (code fuse.Status) {
	return fuse.ENOSYS
}