btrfs_no_std/extent/
extent_inline_ref.rs

1use {
2    byteorder::LE,
3    num_enum::{IntoPrimitive, TryFromPrimitive},
4    static_assertions::const_assert_eq,
5    strum::EnumIter,
6    zerocopy::{AsBytes, FromBytes, Unaligned, U64},
7};
8
9/// This acts as a header for different types of inline extent back references inside extent or
10/// metadata items.
11#[derive(Copy, Clone, Debug, AsBytes, FromBytes, Unaligned)]
12#[repr(C, packed)]
13pub struct ExtentInlineRef {
14    /// The type of reference, which corresponds with a value from [`ExtentInlineRefType`].
15    /// This field also determines the semantic importance of [`offset`].
16    ///
17    /// [`ExtentInlineRefType`]: crate::ExtentInlineRefType
18    /// [`offset`]: ExtentInlineRef::offset
19    pub r#type: u8,
20
21    /// This field has different functions depending on the value of [`type`].
22    ///
23    /// [`type`]: ExtentInlineRef::type
24    pub offset: U64<LE>,
25}
26const_assert_eq!(core::mem::size_of::<ExtentInlineRef>(), 9);
27
28/// The type of [`ExtentInlineRef`].
29///
30/// [`ExtentInlineRef`]: crate::ExtentInlineRef
31#[derive(Copy, Clone, Debug, Hash, PartialEq, EnumIter, IntoPrimitive, TryFromPrimitive)]
32#[repr(u8)]
33pub enum ExtentInlineRefType {
34    /// The reference is indirect for a tree block.
35    ///
36    /// [`offset`] contains the object ID of the tree root that allocated the block.
37    ///
38    /// [`offset`]: ExtentInlineRef::offset
39    TreeBlockRef = 176,
40
41    /// The reference is shared for a tree block.
42    ///
43    /// [`offset`] contains the byte offset of the node one level above in the tree where this block
44    /// is located.
45    ///
46    /// [`offset`]: ExtentInlineRef::offset
47    SharedBlockRef = 182,
48
49    /// The reference is indirect for a data extent.
50    ///
51    /// An `ExtentDataRef` is located immediately after the [`type`] field and overlaps the unused
52    /// [`offset`] field.
53    ///
54    /// [`type`]: ExtentInlineRef::type
55    /// [`offset`]: ExtentInlineRef::offset
56    ExtentDataRef = 178,
57
58    /// The reference is shared for a data extent.
59    ///
60    /// [`offset`] contains the byte offset of the metadata that contains the extent data item that
61    /// describes this extent.
62    ///
63    /// Immediately following [`offset`] (and the end of [`ExtentInlineRef`] structure) is a
64    /// [`SharedDataRef`] that contains the reference count.
65    ///
66    /// [`offset`]: ExtentInlineRef::offset
67    /// [`ExtentInlineRef`]: crate::ExtentInlineRef
68    /// [`SharedDataRef`]: crate::SharedDataRef
69    SharedDataRef = 184,
70}
btrfs_no_std/extent/extent_inline_ref.rs

btrfs_no_std/extent/
extent_inline_ref.rs
