From 7951b76258a3683f0610aa007e1dd1cadf72ed92 Mon Sep 17 00:00:00 2001
From: Andrew Walbran <qwandor@google.com>
Date: Wed, 7 Aug 2024 17:30:53 +0100
Subject: [PATCH] Implement embedded-io traits for File.

---
 CHANGELOG.md            |  2 +-
 Cargo.toml              |  1 +
 src/filesystem/files.rs | 78 ++++++++++++++++++++++++++++++++++++++++-
 src/lib.rs              | 36 +++++++++++++++++++
 4 files changed, 115 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ecb40f3..3361d1a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,7 +12,7 @@ The format is based on [Keep a Changelog] and this project adheres to [Semantic
 
 ### Added
 
-- None
+- `File` now implements the `embedded-io` `Read`, `Write` and `Seek` traits.
 
 ### Removed
 
diff --git a/Cargo.toml b/Cargo.toml
index 88412f7..45276c1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,7 @@ version = "0.8.0"
 byteorder = {version = "1", default-features = false}
 defmt = {version = "0.3", optional = true}
 embedded-hal = "1.0.0"
+embedded-io = "0.6.1"
 heapless = "^0.8"
 log = {version = "0.4", default-features = false, optional = true}
 
diff --git a/src/filesystem/files.rs b/src/filesystem/files.rs
index 5e52477..1b13e09 100644
--- a/src/filesystem/files.rs
+++ b/src/filesystem/files.rs
@@ -1,7 +1,9 @@
+use super::TimeSource;
 use crate::{
     filesystem::{ClusterId, DirEntry, SearchId},
-    Error, RawVolume, VolumeManager,
+    BlockDevice, Error, RawVolume, VolumeManager,
 };
+use embedded_io::{ErrorType, Read, Seek, SeekFrom, Write};
 
 /// A handle for an open file on disk.
 ///
@@ -165,6 +167,80 @@ where
     }
 }
 
+impl<
+        D: BlockDevice,
+        T: TimeSource,
+        const MAX_DIRS: usize,
+        const MAX_FILES: usize,
+        const MAX_VOLUMES: usize,
+    > ErrorType for File<'_, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
+{
+    type Error = crate::Error<D::Error>;
+}
+
+impl<
+        D: BlockDevice,
+        T: TimeSource,
+        const MAX_DIRS: usize,
+        const MAX_FILES: usize,
+        const MAX_VOLUMES: usize,
+    > Read for File<'_, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
+{
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
+        if buf.is_empty() {
+            Ok(0)
+        } else {
+            self.read(buf)
+        }
+    }
+}
+
+impl<
+        D: BlockDevice,
+        T: TimeSource,
+        const MAX_DIRS: usize,
+        const MAX_FILES: usize,
+        const MAX_VOLUMES: usize,
+    > Write for File<'_, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
+{
+    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
+        if buf.is_empty() {
+            Ok(0)
+        } else {
+            self.write(buf)?;
+            Ok(buf.len())
+        }
+    }
+
+    fn flush(&mut self) -> Result<(), Self::Error> {
+        self.flush()
+    }
+}
+
+impl<
+        D: BlockDevice,
+        T: TimeSource,
+        const MAX_DIRS: usize,
+        const MAX_FILES: usize,
+        const MAX_VOLUMES: usize,
+    > Seek for File<'_, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
+{
+    fn seek(&mut self, pos: SeekFrom) -> Result<u64, Self::Error> {
+        match pos {
+            SeekFrom::Start(offset) => {
+                self.seek_from_start(offset.try_into().map_err(|_| Error::InvalidOffset)?)?
+            }
+            SeekFrom::End(offset) => {
+                self.seek_from_end((-offset).try_into().map_err(|_| Error::InvalidOffset)?)?
+            }
+            SeekFrom::Current(offset) => {
+                self.seek_from_current(offset.try_into().map_err(|_| Error::InvalidOffset)?)?
+            }
+        }
+        Ok(self.offset().into())
+    }
+}
+
 #[cfg(feature = "defmt-log")]
 impl<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize>
     defmt::Format for File<'a, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
diff --git a/src/lib.rs b/src/lib.rs
index f1c4e02..f510571 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -73,6 +73,8 @@ pub mod fat;
 pub mod filesystem;
 pub mod sdcard;
 
+use core::fmt::Debug;
+use embedded_io::ErrorKind;
 use filesystem::SearchId;
 
 #[doc(inline)]
@@ -202,6 +204,40 @@ where
     DirAlreadyExists,
 }
 
+impl<E: Debug> embedded_io::Error for Error<E> {
+    fn kind(&self) -> ErrorKind {
+        match self {
+            Error::DeviceError(_)
+            | Error::FormatError(_)
+            | Error::FileAlreadyOpen
+            | Error::DirAlreadyOpen
+            | Error::VolumeStillInUse
+            | Error::VolumeAlreadyOpen
+            | Error::EndOfFile
+            | Error::DiskFull
+            | Error::NotEnoughSpace
+            | Error::AllocationError => ErrorKind::Other,
+            Error::NoSuchVolume
+            | Error::FilenameError(_)
+            | Error::BadHandle
+            | Error::InvalidOffset => ErrorKind::InvalidInput,
+            Error::TooManyOpenVolumes | Error::TooManyOpenDirs | Error::TooManyOpenFiles => {
+                ErrorKind::OutOfMemory
+            }
+            Error::NotFound => ErrorKind::NotFound,
+            Error::OpenedDirAsFile
+            | Error::OpenedFileAsDir
+            | Error::DeleteDirAsFile
+            | Error::BadCluster
+            | Error::ConversionError
+            | Error::UnterminatedFatChain => ErrorKind::InvalidData,
+            Error::Unsupported | Error::BadBlockSize(_) => ErrorKind::Unsupported,
+            Error::ReadOnly => ErrorKind::PermissionDenied,
+            Error::FileAlreadyExists | Error::DirAlreadyExists => ErrorKind::AlreadyExists,
+        }
+    }
+}
+
 impl<E> From<E> for Error<E>
 where
     E: core::fmt::Debug,