refactor(io): make accurate reader names primary (#4060)

crates/io-core/src/direct_io.rs

@@ -101,7 +101,7 @@ impl From<io::Error> for DirectIoError {
 /// let reader = AlignedPreadReader::new(file, offset, size)?;
 /// ```
 #[cfg(target_os = "linux")]
-pub struct DirectIoReader {
+pub struct AlignedPreadReader {
     /// Underlying file handle used for aligned pread I/O
     file: std::fs::File,
     /// Current read position
@@ -117,7 +117,7 @@ pub struct DirectIoReader {
 }
 
 #[cfg(target_os = "linux")]
-impl DirectIoReader {
+impl AlignedPreadReader {
     /// Alignment requirement for reads (512 bytes for most systems)
     pub const ALIGNMENT: usize = 512;
 
@@ -131,7 +131,7 @@ impl DirectIoReader {
     ///
     /// # Returns
     ///
-    /// A `DirectIoReader` that reads the file at the given offset.
+    /// An `AlignedPreadReader` that reads the file at the given offset.
     ///
     /// # Errors
     ///
@@ -197,7 +197,7 @@ impl DirectIoReader {
 }
 
 #[cfg(target_os = "linux")]
-impl AsyncRead for DirectIoReader {
+impl AsyncRead for AlignedPreadReader {
     fn poll_read(mut self: Pin<&mut Self>, _cx: &mut Context<'_>, buf: &mut ReadBuf<'_>) -> Poll<io::Result<()>> {
         let filled = buf.filled().len();
         let mut remaining = buf.initialize_unfilled();
@@ -222,12 +222,12 @@ impl AsyncRead for DirectIoReader {
 /// On non-Linux platforms, `read_at`-based I/O is not available through this
 /// type. This stub exists to provide a consistent API across platforms.
 #[cfg(not(target_os = "linux"))]
-pub struct DirectIoReader {
+pub struct AlignedPreadReader {
     _priv: (),
 }
 
 #[cfg(not(target_os = "linux"))]
-impl DirectIoReader {
+impl AlignedPreadReader {
     /// Create a new aligned pread reader (not supported on this platform).
     ///
     /// Always returns an error on non-Linux platforms.
@@ -237,7 +237,7 @@ impl DirectIoReader {
 }
 
 #[cfg(not(target_os = "linux"))]
-impl AsyncRead for DirectIoReader {
+impl AsyncRead for AlignedPreadReader {
     fn poll_read(self: Pin<&mut Self>, _cx: &mut Context<'_>, _buf: &mut ReadBuf<'_>) -> Poll<io::Result<()>> {
         Poll::Ready(Err(io::Error::new(
             io::ErrorKind::Unsupported,
@@ -246,11 +246,11 @@ impl AsyncRead for DirectIoReader {
     }
 }
 
-impl std::fmt::Debug for DirectIoReader {
+impl std::fmt::Debug for AlignedPreadReader {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         #[cfg(target_os = "linux")]
         {
-            f.debug_struct("DirectIoReader")
+            f.debug_struct("AlignedPreadReader")
                 .field("pos", &self.pos)
                 .field("remaining", &self.remaining)
                 .field("buffer_len", &self.buffer_len)
@@ -258,7 +258,9 @@ impl std::fmt::Debug for DirectIoReader {
         }
         #[cfg(not(target_os = "linux"))]
         {
-            f.debug_struct("DirectIoReader").field("platform", &"unsupported").finish()
+            f.debug_struct("AlignedPreadReader")
+                .field("platform", &"unsupported")
+                .finish()
         }
     }
 }
@@ -266,8 +268,9 @@ impl std::fmt::Debug for DirectIoReader {
 /// Preferred name for aligned pread errors.
 pub type AlignedPreadError = DirectIoError;
 
-/// Preferred name for the aligned pread-based reader.
-pub type AlignedPreadReader = DirectIoReader;
+/// Historical name for the aligned pread-based reader.
+#[deprecated(since = "1.0.0-beta.8", note = "use AlignedPreadReader; this reader does not set O_DIRECT")]
+pub type DirectIoReader = AlignedPreadReader;
 
 #[cfg(test)]
 mod tests {
@@ -279,7 +282,10 @@ mod tests {
         {
             // Valid alignment
             let file = std::fs::File::open("/dev/zero").unwrap();
-            assert!(DirectIoReader::new(file, 0, 512).is_ok(), "Should succeed with aligned offset and size");
+            assert!(
+                AlignedPreadReader::new(file, 0, 512).is_ok(),
+                "Should succeed with aligned offset and size"
+            );
 
             let file = std::fs::File::open("/dev/zero").expect("open /dev/zero for alias");
             assert!(
@@ -289,16 +295,32 @@ mod tests {
 
             // Invalid offset
             let file = std::fs::File::open("/dev/zero").unwrap();
-            assert!(DirectIoReader::new(file, 1, 512).is_err(), "Should fail with unaligned offset");
+            assert!(AlignedPreadReader::new(file, 1, 512).is_err(), "Should fail with unaligned offset");
 
             // Invalid size
             let file = std::fs::File::open("/dev/zero").unwrap();
-            assert!(DirectIoReader::new(file, 0, 511).is_err(), "Should fail with unaligned size");
+            assert!(AlignedPreadReader::new(file, 0, 511).is_err(), "Should fail with unaligned size");
         }
 
         #[cfg(not(target_os = "linux"))]
         {
             // Non-Linux should return UnsupportedPlatform
+            let file = std::fs::File::open(std::env::current_exe().unwrap()).unwrap();
+            assert!(matches!(AlignedPreadReader::new(file, 0, 512), Err(DirectIoError::UnsupportedPlatform)));
+        }
+    }
+
+    #[test]
+    #[allow(deprecated)]
+    fn test_legacy_direct_io_alias() {
+        #[cfg(target_os = "linux")]
+        {
+            let file = std::fs::File::open("/dev/zero").unwrap();
+            assert!(DirectIoReader::new(file, 0, 512).is_ok());
+        }
+
+        #[cfg(not(target_os = "linux"))]
+        {
             let file = std::fs::File::open(std::env::current_exe().unwrap()).unwrap();
             assert!(matches!(DirectIoReader::new(file, 0, 512), Err(DirectIoError::UnsupportedPlatform)));
         }