From f05307f98aae78c1134494f5bf2d547ae952c115 Mon Sep 17 00:00:00 2001
From: ssy <879650736@qq.com>
Date: Sat, 28 Jun 2025 05:11:29 +0000
Subject: [PATCH 1/4] add urandom

---
 axfs_devfs/src/lib.rs     |  2 ++
 axfs_devfs/src/urandom.rs | 68 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 axfs_devfs/src/urandom.rs

diff --git a/axfs_devfs/src/lib.rs b/axfs_devfs/src/lib.rs
index 1e91629..4cf2193 100644
--- a/axfs_devfs/src/lib.rs
+++ b/axfs_devfs/src/lib.rs
@@ -8,6 +8,7 @@ extern crate alloc;
 
 mod dir;
 mod null;
+mod urandom;
 mod zero;
 
 #[cfg(test)]
@@ -15,6 +16,7 @@ mod tests;
 
 pub use self::dir::DirNode;
 pub use self::null::NullDev;
+pub use self::urandom::UrandomDev;
 pub use self::zero::ZeroDev;
 
 use alloc::sync::Arc;
diff --git a/axfs_devfs/src/urandom.rs b/axfs_devfs/src/urandom.rs
new file mode 100644
index 0000000..1c35f3e
--- /dev/null
+++ b/axfs_devfs/src/urandom.rs
@@ -0,0 +1,68 @@
+use axfs_vfs::{VfsNodeAttr, VfsNodeOps, VfsNodePerm, VfsNodeType, VfsResult};
+use core::sync::atomic::{AtomicU64, Ordering};
+
+/// A urandom device behaves like `/dev/urandom`.
+///
+/// It produces random bytes when read.
+pub struct UrandomDev {
+    seed: AtomicU64,
+}
+
+impl UrandomDev {
+    pub fn new() -> Self {
+        Self {
+            seed: AtomicU64::new(0xa2ce_a2ce),
+        }
+    }
+
+    /// LCG pseudo-random number generator
+    fn next_u64(&self) -> u64 {
+        let new_seed = self
+            .seed
+            .load(Ordering::SeqCst)
+            .wrapping_mul(6364136223846793005)
+            + 1;
+        self.seed.store(new_seed, Ordering::SeqCst);
+        new_seed
+    }
+}
+
+impl Default for UrandomDev {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl VfsNodeOps for UrandomDev {
+    fn get_attr(&self) -> VfsResult<VfsNodeAttr> {
+        Ok(VfsNodeAttr::new(
+            VfsNodePerm::default_file(),
+            VfsNodeType::CharDevice,
+            0,
+            0,
+        ))
+    }
+
+    fn read_at(&self, _offset: u64, buf: &mut [u8]) -> VfsResult<usize> {
+        for chunk in buf.chunks_mut(8) {
+            let random_value = self.next_u64();
+            let bytes = random_value.to_ne_bytes();
+            for (i, byte) in chunk.iter_mut().enumerate() {
+                if i < bytes.len() {
+                    *byte = bytes[i];
+                }
+            }
+        }
+        Ok(buf.len())
+    }
+
+    fn write_at(&self, _offset: u64, buf: &[u8]) -> VfsResult<usize> {
+        Ok(buf.len())
+    }
+
+    fn truncate(&self, _size: u64) -> VfsResult {
+        Ok(())
+    }
+
+    axfs_vfs::impl_vfs_non_dir_default! {}
+}

From 73c69620ad4279242a538adee3eb86e8ab1b0aae Mon Sep 17 00:00:00 2001
From: ssy <879650736@qq.com>
Date: Sat, 28 Jun 2025 05:15:25 +0000
Subject: [PATCH 2/4] add documentation

---
 axfs_devfs/src/urandom.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/axfs_devfs/src/urandom.rs b/axfs_devfs/src/urandom.rs
index 1c35f3e..74d9e7d 100644
--- a/axfs_devfs/src/urandom.rs
+++ b/axfs_devfs/src/urandom.rs
@@ -9,6 +9,7 @@ pub struct UrandomDev {
 }
 
 impl UrandomDev {
+    /// Create a new instance of the urandom device.
     pub fn new() -> Self {
         Self {
             seed: AtomicU64::new(0xa2ce_a2ce),

From 8c47106aff41b0acdea0a2cc6b8e860ebda1958f Mon Sep 17 00:00:00 2001
From: ssy <879650736@qq.com>
Date: Sat, 28 Jun 2025 06:45:39 +0000
Subject: [PATCH 3/4] Fixed UrandomDev's constructor to accept a seed parameter

---
 axfs_devfs/src/urandom.rs | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/axfs_devfs/src/urandom.rs b/axfs_devfs/src/urandom.rs
index 74d9e7d..e2ca11e 100644
--- a/axfs_devfs/src/urandom.rs
+++ b/axfs_devfs/src/urandom.rs
@@ -10,12 +10,17 @@ pub struct UrandomDev {
 
 impl UrandomDev {
     /// Create a new instance of the urandom device.
-    pub fn new() -> Self {
+    pub fn new(seed: u64) -> Self {
         Self {
-            seed: AtomicU64::new(0xa2ce_a2ce),
+            seed: AtomicU64::new(seed),
         }
     }
 
+    /// Create a new instance with a default seed.
+    fn new_with_default_seed() -> Self {
+        Self::new(0xa2ce_a2ce)
+    }
+
     /// LCG pseudo-random number generator
     fn next_u64(&self) -> u64 {
         let new_seed = self
@@ -30,7 +35,7 @@ impl UrandomDev {
 
 impl Default for UrandomDev {
     fn default() -> Self {
-        Self::new()
+        Self::new_with_default_seed()
     }
 }
 

From 486eccb0e74ab7fd76f316dcd8dfa5dc6dacd151 Mon Sep 17 00:00:00 2001
From: ssy <879650736@qq.com>
Date: Sat, 28 Jun 2025 07:43:31 +0000
Subject: [PATCH 4/4] Change the constructor of UrandomDev to a constant
 function

---
 axfs_devfs/src/urandom.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/axfs_devfs/src/urandom.rs b/axfs_devfs/src/urandom.rs
index e2ca11e..53d180f 100644
--- a/axfs_devfs/src/urandom.rs
+++ b/axfs_devfs/src/urandom.rs
@@ -10,7 +10,7 @@ pub struct UrandomDev {
 
 impl UrandomDev {
     /// Create a new instance of the urandom device.
-    pub fn new(seed: u64) -> Self {
+    pub const fn new(seed: u64) -> Self {
         Self {
             seed: AtomicU64::new(seed),
         }