src/pxar/fuse.rs: add function to map offset to inode and vice versa

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
This commit is contained in:
Christian Ebner 2019-09-03 14:14:30 +02:00 committed by Dietmar Maurer
parent c7fee396c6
commit 75933d1e83

View File

@ -14,12 +14,13 @@ use libc::{c_char, c_int, c_void, size_t};
use libc;
use super::decoder::Decoder;
use super::format_definition::PxarGoodbyeItem;
/// Node ID of the root inode
/// This is the only one whose ID is not equal to the offset in the file.
/// This is ok since offset 1 is part of the entry header and will therefore
/// not occur again, but remapping to the correct offset of 0 is required.
//const FUSE_ROOT_ID: u64 = 1;
const FUSE_ROOT_ID: u64 = 1;
fn decoder_callback(path: &Path) -> Result<(), Error> {
println!("{:#?}", path);
@ -246,6 +247,38 @@ impl Drop for Session {
}
}
const GOODBYE_ITEM_SIZE: u64 = std::mem::size_of::<PxarGoodbyeItem>() as u64;
/// Converts the inode to the file offset
///
/// Since the inodes are defined as the file offset,
/// this simply returns the inode value.
/// The only exception to this is the inode of root,
/// which is defined as `FUSE_ROOT_ID` by libfuse and therefore mapped
/// to the roots goodbye table tail.
fn inode_to_offset(inode: u64, root_end: u64) -> u64 {
if inode == FUSE_ROOT_ID {
root_end - GOODBYE_ITEM_SIZE
} else {
inode
}
}
/// Converts the file offset to an inode
///
/// Since the inodes are defined as the file offset,
/// this simply returns the offset value.
/// The only exception to this is the inode of root,
/// which is defined as `FUSE_ROOT_ID` by libfuse, so the roots goodbye tail
/// offset gets mapped to `FUSE_ROOT_ID`.
pub(crate) fn offset_to_inode(offset: u64, root_end: u64) -> u64 {
if offset == root_end - GOODBYE_ITEM_SIZE {
FUSE_ROOT_ID
} else {
offset
}
}
/// Creates a context providing an exclusive mutable reference to the decoder.
///
/// Each callback function needing access to the decoder can easily get an