[RFC PATCH 11/24] erofs: add map data structure in Rust

[Yiyang Wu <toolmanp@tlmp.cc>]

This patch introduce core map flags and runtime map data structure
in Rust. This will later be used to do iomapping.

Signed-off-by: Yiyang Wu <toolmanp@tlmp.cc>
---
 fs/erofs/rust/erofs_sys.rs     |  1 +
 fs/erofs/rust/erofs_sys/map.rs | 45 ++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 fs/erofs/rust/erofs_sys/map.rs

diff --git a/fs/erofs/rust/erofs_sys.rs b/fs/erofs/rust/erofs_sys.rs
index f1a1e491caec..15ed65866097 100644
--- a/fs/erofs/rust/erofs_sys.rs
+++ b/fs/erofs/rust/erofs_sys.rs
@@ -28,6 +28,7 @@
 pub(crate) mod devices;
 pub(crate) mod errnos;
 pub(crate) mod inode;
+pub(crate) mod map;
 pub(crate) mod superblock;
 pub(crate) mod xattrs;
 pub(crate) use errnos::Errno;
diff --git a/fs/erofs/rust/erofs_sys/map.rs b/fs/erofs/rust/erofs_sys/map.rs
new file mode 100644
index 000000000000..757e8083c8f1
--- /dev/null
+++ b/fs/erofs/rust/erofs_sys/map.rs
@@ -0,0 +1,45 @@
+// Copyright 2024 Yiyang Wu
+// SPDX-License-Identifier: MIT or GPL-2.0-or-later
+
+use super::*;
+pub(crate) const MAP_MAPPED: u32 = 0x0001;
+pub(crate) const MAP_META: u32 = 0x0002;
+pub(crate) const MAP_ENCODED: u32 = 0x0004;
+pub(crate) const MAP_FULL_MAPPED: u32 = 0x0008;
+pub(crate) const MAP_FRAGMENT: u32 = 0x0010;
+pub(crate) const MAP_PARTIAL_REF: u32 = 0x0020;
+
+#[derive(Debug, Default)]
+#[repr(C)]
+pub(crate) struct Segment {
+    pub(crate) start: Off,
+    pub(crate) len: Off,
+}
+
+#[derive(Debug, Default)]
+#[repr(C)]
+pub(crate) struct Map {
+    pub(crate) logical: Segment,
+    pub(crate) physical: Segment,
+    pub(crate) device_id: u16,
+    pub(crate) algorithm_format: u16,
+    pub(crate) map_type: MapType,
+}
+
+#[derive(Debug, Default)]
+pub(crate) enum MapType {
+    Meta,
+    #[default]
+    Normal,
+}
+
+impl From<MapType> for u32 {
+    fn from(value: MapType) -> Self {
+        match value {
+            MapType::Meta => MAP_META | MAP_MAPPED,
+            MapType::Normal => MAP_MAPPED,
+        }
+    }
+}
+
+pub(crate) type MapResult = PosixResult<Map>;
-- 
2.46.0