Re-structure sat-rs

- Add new shared subcrate satrs-shared to split off some shared
  components not expected to change very often.
- Renmame `satrs-core` to `satrs`. It is expected that sat-rs will remain
  the primary crate, so the core information is superfluous, and core also
  implies stability, which will not be the case for some time.

satrs/src/cfdp/filestore.rs

@@ -0,0 +1,770 @@
+use alloc::string::{String, ToString};
+use core::fmt::Display;
+use crc::{Crc, CRC_32_CKSUM};
+use spacepackets::cfdp::ChecksumType;
+use spacepackets::ByteConversionError;
+#[cfg(feature = "std")]
+use std::error::Error;
+use std::path::Path;
+#[cfg(feature = "std")]
+pub use stdmod::*;
+
+pub const CRC_32: Crc<u32> = Crc::<u32>::new(&CRC_32_CKSUM);
+
+#[derive(Debug, Clone)]
+pub enum FilestoreError {
+    FileDoesNotExist,
+    FileAlreadyExists,
+    DirDoesNotExist,
+    Permission,
+    IsNotFile,
+    IsNotDirectory,
+    ByteConversion(ByteConversionError),
+    Io {
+        raw_errno: Option<i32>,
+        string: String,
+    },
+    ChecksumTypeNotImplemented(ChecksumType),
+}
+
+impl From<ByteConversionError> for FilestoreError {
+    fn from(value: ByteConversionError) -> Self {
+        Self::ByteConversion(value)
+    }
+}
+
+impl Display for FilestoreError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            FilestoreError::FileDoesNotExist => {
+                write!(f, "file does not exist")
+            }
+            FilestoreError::FileAlreadyExists => {
+                write!(f, "file already exists")
+            }
+            FilestoreError::DirDoesNotExist => {
+                write!(f, "directory does not exist")
+            }
+            FilestoreError::Permission => {
+                write!(f, "permission error")
+            }
+            FilestoreError::IsNotFile => {
+                write!(f, "is not a file")
+            }
+            FilestoreError::IsNotDirectory => {
+                write!(f, "is not a directory")
+            }
+            FilestoreError::ByteConversion(e) => {
+                write!(f, "filestore error: {e}")
+            }
+            FilestoreError::Io { raw_errno, string } => {
+                write!(
+                    f,
+                    "filestore generic IO error with raw errno {:?}: {}",
+                    raw_errno, string
+                )
+            }
+            FilestoreError::ChecksumTypeNotImplemented(checksum_type) => {
+                write!(f, "checksum {:?} not implemented", checksum_type)
+            }
+        }
+    }
+}
+
+impl Error for FilestoreError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match self {
+            FilestoreError::ByteConversion(e) => Some(e),
+            _ => None,
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl From<std::io::Error> for FilestoreError {
+    fn from(value: std::io::Error) -> Self {
+        Self::Io {
+            raw_errno: value.raw_os_error(),
+            string: value.to_string(),
+        }
+    }
+}
+
+pub trait VirtualFilestore {
+    fn create_file(&self, file_path: &str) -> Result<(), FilestoreError>;
+
+    fn remove_file(&self, file_path: &str) -> Result<(), FilestoreError>;
+
+    /// Truncating a file means deleting all its data so the resulting file is empty.
+    /// This can be more efficient than removing and re-creating a file.
+    fn truncate_file(&self, file_path: &str) -> Result<(), FilestoreError>;
+
+    fn remove_dir(&self, dir_path: &str, all: bool) -> Result<(), FilestoreError>;
+    fn create_dir(&self, dir_path: &str) -> Result<(), FilestoreError>;
+
+    fn read_data(
+        &self,
+        file_path: &str,
+        offset: u64,
+        read_len: u64,
+        buf: &mut [u8],
+    ) -> Result<(), FilestoreError>;
+
+    fn write_data(&self, file: &str, offset: u64, buf: &[u8]) -> Result<(), FilestoreError>;
+
+    fn filename_from_full_path(path: &str) -> Option<&str>
+    where
+        Self: Sized,
+    {
+        // Convert the path string to a Path
+        let path = Path::new(path);
+
+        // Extract the file name using the file_name() method
+        path.file_name().and_then(|name| name.to_str())
+    }
+
+    fn is_file(&self, path: &str) -> bool;
+
+    fn is_dir(&self, path: &str) -> bool {
+        !self.is_file(path)
+    }
+
+    fn exists(&self, path: &str) -> bool;
+
+    /// This special function is the CFDP specific abstraction to verify the checksum of a file.
+    /// This allows to keep OS specific details like reading the whole file in the most efficient
+    /// manner inside the file system abstraction.
+    ///
+    /// The passed verification buffer argument will be used by the specific implementation as
+    /// a buffer to read the file into. It is recommended to use common buffer sizes like
+    /// 4096 or 8192 bytes.
+    fn checksum_verify(
+        &self,
+        file_path: &str,
+        checksum_type: ChecksumType,
+        expected_checksum: u32,
+        verification_buf: &mut [u8],
+    ) -> Result<bool, FilestoreError>;
+}
+
+#[cfg(feature = "std")]
+pub mod stdmod {
+    use super::*;
+    use std::{
+        fs::{self, File, OpenOptions},
+        io::{BufReader, Read, Seek, SeekFrom, Write},
+        path::Path,
+    };
+
+    #[derive(Default)]
+    pub struct NativeFilestore {}
+
+    impl VirtualFilestore for NativeFilestore {
+        fn create_file(&self, file_path: &str) -> Result<(), FilestoreError> {
+            if self.exists(file_path) {
+                return Err(FilestoreError::FileAlreadyExists);
+            }
+            File::create(file_path)?;
+            Ok(())
+        }
+
+        fn remove_file(&self, file_path: &str) -> Result<(), FilestoreError> {
+            if !self.exists(file_path) {
+                return Err(FilestoreError::FileDoesNotExist);
+            }
+            if !self.is_file(file_path) {
+                return Err(FilestoreError::IsNotFile);
+            }
+            fs::remove_file(file_path)?;
+            Ok(())
+        }
+
+        fn truncate_file(&self, file_path: &str) -> Result<(), FilestoreError> {
+            if !self.exists(file_path) {
+                return Err(FilestoreError::FileDoesNotExist);
+            }
+            if !self.is_file(file_path) {
+                return Err(FilestoreError::IsNotFile);
+            }
+            OpenOptions::new()
+                .write(true)
+                .truncate(true)
+                .open(file_path)?;
+            Ok(())
+        }
+
+        fn create_dir(&self, dir_path: &str) -> Result<(), FilestoreError> {
+            fs::create_dir(dir_path).map_err(|e| FilestoreError::Io {
+                raw_errno: e.raw_os_error(),
+                string: e.to_string(),
+            })?;
+            Ok(())
+        }
+
+        fn remove_dir(&self, dir_path: &str, all: bool) -> Result<(), FilestoreError> {
+            if !self.exists(dir_path) {
+                return Err(FilestoreError::DirDoesNotExist);
+            }
+            if !self.is_dir(dir_path) {
+                return Err(FilestoreError::IsNotDirectory);
+            }
+            if !all {
+                fs::remove_dir(dir_path)?;
+                return Ok(());
+            }
+            fs::remove_dir_all(dir_path)?;
+            Ok(())
+        }
+
+        fn read_data(
+            &self,
+            file_name: &str,
+            offset: u64,
+            read_len: u64,
+            buf: &mut [u8],
+        ) -> Result<(), FilestoreError> {
+            if buf.len() < read_len as usize {
+                return Err(ByteConversionError::ToSliceTooSmall {
+                    found: buf.len(),
+                    expected: read_len as usize,
+                }
+                .into());
+            }
+            if !self.exists(file_name) {
+                return Err(FilestoreError::FileDoesNotExist);
+            }
+            if !self.is_file(file_name) {
+                return Err(FilestoreError::IsNotFile);
+            }
+            let mut file = File::open(file_name)?;
+            file.seek(SeekFrom::Start(offset))?;
+            file.read_exact(&mut buf[0..read_len as usize])?;
+            Ok(())
+        }
+
+        fn write_data(&self, file: &str, offset: u64, buf: &[u8]) -> Result<(), FilestoreError> {
+            if !self.exists(file) {
+                return Err(FilestoreError::FileDoesNotExist);
+            }
+            if !self.is_file(file) {
+                return Err(FilestoreError::IsNotFile);
+            }
+            let mut file = OpenOptions::new().write(true).open(file)?;
+            file.seek(SeekFrom::Start(offset))?;
+            file.write_all(buf)?;
+            Ok(())
+        }
+
+        fn is_file(&self, path: &str) -> bool {
+            let path = Path::new(path);
+            path.is_file()
+        }
+
+        fn exists(&self, path: &str) -> bool {
+            let path = Path::new(path);
+            if !path.exists() {
+                return false;
+            }
+            true
+        }
+
+        fn checksum_verify(
+            &self,
+            file_path: &str,
+            checksum_type: ChecksumType,
+            expected_checksum: u32,
+            verification_buf: &mut [u8],
+        ) -> Result<bool, FilestoreError> {
+            match checksum_type {
+                ChecksumType::Modular => {
+                    if self.calc_modular_checksum(file_path)? == expected_checksum {
+                        return Ok(true);
+                    }
+                    Ok(false)
+                }
+                ChecksumType::Crc32 => {
+                    let mut digest = CRC_32.digest();
+                    let file_to_check = File::open(file_path)?;
+                    let mut buf_reader = BufReader::new(file_to_check);
+                    loop {
+                        let bytes_read = buf_reader.read(verification_buf)?;
+                        if bytes_read == 0 {
+                            break;
+                        }
+                        digest.update(&verification_buf[0..bytes_read]);
+                    }
+                    if digest.finalize() == expected_checksum {
+                        return Ok(true);
+                    }
+                    Ok(false)
+                }
+                ChecksumType::NullChecksum => Ok(true),
+                _ => Err(FilestoreError::ChecksumTypeNotImplemented(checksum_type)),
+            }
+        }
+    }
+
+    impl NativeFilestore {
+        pub fn calc_modular_checksum(&self, file_path: &str) -> Result<u32, FilestoreError> {
+            let mut checksum: u32 = 0;
+            let file = File::open(file_path)?;
+            let mut buf_reader = BufReader::new(file);
+            let mut buffer = [0; 4];
+
+            loop {
+                let bytes_read = buf_reader.read(&mut buffer)?;
+                if bytes_read == 0 {
+                    break;
+                }
+                // Perform padding directly in the buffer
+                (bytes_read..4).for_each(|i| {
+                    buffer[i] = 0;
+                });
+
+                checksum = checksum.wrapping_add(u32::from_be_bytes(buffer));
+            }
+            Ok(checksum)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::{fs, path::Path, println};
+
+    use super::*;
+    use alloc::format;
+    use tempfile::tempdir;
+
+    const EXAMPLE_DATA_CFDP: [u8; 15] = [
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
+    ];
+
+    const NATIVE_FS: NativeFilestore = NativeFilestore {};
+
+    #[test]
+    fn test_basic_native_filestore_create() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        let result =
+            NATIVE_FS.create_file(file_path.to_str().expect("getting str for file failed"));
+        assert!(result.is_ok());
+        let path = Path::new(&file_path);
+        assert!(path.exists());
+        assert!(NATIVE_FS.exists(file_path.to_str().unwrap()));
+        assert!(NATIVE_FS.is_file(file_path.to_str().unwrap()));
+    }
+
+    #[test]
+    fn test_basic_native_fs_file_exists() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        assert!(!NATIVE_FS.exists(file_path.to_str().unwrap()));
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        assert!(NATIVE_FS.exists(file_path.to_str().unwrap()));
+        assert!(NATIVE_FS.is_file(file_path.to_str().unwrap()));
+    }
+
+    #[test]
+    fn test_basic_native_fs_dir_exists() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let dir_path = tmpdir.path().join("testdir");
+        assert!(!NATIVE_FS.exists(dir_path.to_str().unwrap()));
+        NATIVE_FS
+            .create_dir(dir_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        assert!(NATIVE_FS.exists(dir_path.to_str().unwrap()));
+        assert!(NATIVE_FS.is_dir(dir_path.as_path().to_str().unwrap()));
+    }
+
+    #[test]
+    fn test_basic_native_fs_remove_file() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .expect("creating file failed");
+        assert!(NATIVE_FS.exists(file_path.to_str().unwrap()));
+        NATIVE_FS
+            .remove_file(file_path.to_str().unwrap())
+            .expect("removing file failed");
+        assert!(!NATIVE_FS.exists(file_path.to_str().unwrap()));
+    }
+
+    #[test]
+    fn test_basic_native_fs_write() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        assert!(!NATIVE_FS.exists(file_path.to_str().unwrap()));
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        assert!(NATIVE_FS.exists(file_path.to_str().unwrap()));
+        assert!(NATIVE_FS.is_file(file_path.to_str().unwrap()));
+        println!("{}", file_path.to_str().unwrap());
+        let write_data = "hello world\n";
+        NATIVE_FS
+            .write_data(file_path.to_str().unwrap(), 0, write_data.as_bytes())
+            .expect("writing to file failed");
+        let read_back = fs::read_to_string(file_path).expect("reading back data failed");
+        assert_eq!(read_back, write_data);
+    }
+
+    #[test]
+    fn test_basic_native_fs_read() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        assert!(!NATIVE_FS.exists(file_path.to_str().unwrap()));
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        assert!(NATIVE_FS.exists(file_path.to_str().unwrap()));
+        assert!(NATIVE_FS.is_file(file_path.to_str().unwrap()));
+        println!("{}", file_path.to_str().unwrap());
+        let write_data = "hello world\n";
+        NATIVE_FS
+            .write_data(file_path.to_str().unwrap(), 0, write_data.as_bytes())
+            .expect("writing to file failed");
+        let read_back = fs::read_to_string(file_path).expect("reading back data failed");
+        assert_eq!(read_back, write_data);
+    }
+
+    #[test]
+    fn test_truncate_file() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .expect("creating file failed");
+        fs::write(file_path.clone(), [1, 2, 3, 4]).unwrap();
+        assert_eq!(fs::read(file_path.clone()).unwrap(), [1, 2, 3, 4]);
+        NATIVE_FS
+            .truncate_file(file_path.to_str().unwrap())
+            .unwrap();
+        assert_eq!(fs::read(file_path.clone()).unwrap(), []);
+    }
+
+    #[test]
+    fn test_remove_dir() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let dir_path = tmpdir.path().join("testdir");
+        assert!(!NATIVE_FS.exists(dir_path.to_str().unwrap()));
+        NATIVE_FS
+            .create_dir(dir_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        assert!(NATIVE_FS.exists(dir_path.to_str().unwrap()));
+        NATIVE_FS
+            .remove_dir(dir_path.to_str().unwrap(), false)
+            .unwrap();
+        assert!(!NATIVE_FS.exists(dir_path.to_str().unwrap()));
+    }
+
+    #[test]
+    fn test_read_file() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .expect("creating file failed");
+        fs::write(file_path.clone(), [1, 2, 3, 4]).unwrap();
+        let read_buf: &mut [u8] = &mut [0; 4];
+        NATIVE_FS
+            .read_data(file_path.to_str().unwrap(), 0, 4, read_buf)
+            .unwrap();
+        assert_eq!([1, 2, 3, 4], read_buf);
+        NATIVE_FS
+            .write_data(file_path.to_str().unwrap(), 4, &[5, 6, 7, 8])
+            .expect("writing to file failed");
+        NATIVE_FS
+            .read_data(file_path.to_str().unwrap(), 2, 4, read_buf)
+            .unwrap();
+        assert_eq!([3, 4, 5, 6], read_buf);
+    }
+
+    #[test]
+    fn test_remove_which_does_not_exist() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        let result = NATIVE_FS.read_data(file_path.to_str().unwrap(), 0, 4, &mut [0; 4]);
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::FileDoesNotExist = error {
+            assert_eq!(error.to_string(), "file does not exist");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_file_already_exists() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        let result =
+            NATIVE_FS.create_file(file_path.to_str().expect("getting str for file failed"));
+        assert!(result.is_ok());
+        let result =
+            NATIVE_FS.create_file(file_path.to_str().expect("getting str for file failed"));
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::FileAlreadyExists = error {
+            assert_eq!(error.to_string(), "file already exists");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_remove_file_with_dir_api() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        let result = NATIVE_FS.remove_dir(file_path.to_str().unwrap(), true);
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::IsNotDirectory = error {
+            assert_eq!(error.to_string(), "is not a directory");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_remove_dir_remove_all() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let dir_path = tmpdir.path().join("test");
+        NATIVE_FS
+            .create_dir(dir_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        let file_path = dir_path.as_path().join("test.txt");
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        let result = NATIVE_FS.remove_dir(dir_path.to_str().unwrap(), true);
+        assert!(result.is_ok());
+        assert!(!NATIVE_FS.exists(dir_path.to_str().unwrap()));
+    }
+
+    #[test]
+    fn test_remove_dir_with_file_api() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test");
+        NATIVE_FS
+            .create_dir(file_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        let result = NATIVE_FS.remove_file(file_path.to_str().unwrap());
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::IsNotFile = error {
+            assert_eq!(error.to_string(), "is not a file");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_remove_dir_which_does_not_exist() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test");
+        let result = NATIVE_FS.remove_dir(file_path.to_str().unwrap(), true);
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::DirDoesNotExist = error {
+            assert_eq!(error.to_string(), "directory does not exist");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_remove_file_which_does_not_exist() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        let result = NATIVE_FS.remove_file(file_path.to_str().unwrap());
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::FileDoesNotExist = error {
+            assert_eq!(error.to_string(), "file does not exist");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_truncate_file_which_does_not_exist() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        let result = NATIVE_FS.truncate_file(file_path.to_str().unwrap());
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::FileDoesNotExist = error {
+            assert_eq!(error.to_string(), "file does not exist");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_truncate_file_on_directory() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test");
+        NATIVE_FS.create_dir(file_path.to_str().unwrap()).unwrap();
+        let result = NATIVE_FS.truncate_file(file_path.to_str().unwrap());
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::IsNotFile = error {
+            assert_eq!(error.to_string(), "is not a file");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_byte_conversion_error_when_reading() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        let result = NATIVE_FS.read_data(file_path.to_str().unwrap(), 0, 2, &mut []);
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::ByteConversion(byte_conv_error) = error {
+            if let ByteConversionError::ToSliceTooSmall { found, expected } = byte_conv_error {
+                assert_eq!(found, 0);
+                assert_eq!(expected, 2);
+            } else {
+                panic!("unexpected error");
+            }
+            assert_eq!(
+                error.to_string(),
+                format!("filestore error: {}", byte_conv_error)
+            );
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_read_file_on_dir() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let dir_path = tmpdir.path().join("test");
+        NATIVE_FS
+            .create_dir(dir_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        let result = NATIVE_FS.read_data(dir_path.to_str().unwrap(), 0, 4, &mut [0; 4]);
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::IsNotFile = error {
+            assert_eq!(error.to_string(), "is not a file");
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_write_file_non_existing() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        let result = NATIVE_FS.write_data(file_path.to_str().unwrap(), 0, &[]);
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::FileDoesNotExist = error {
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_write_file_on_dir() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test");
+        NATIVE_FS.create_dir(file_path.to_str().unwrap()).unwrap();
+        let result = NATIVE_FS.write_data(file_path.to_str().unwrap(), 0, &[]);
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::IsNotFile = error {
+        } else {
+            panic!("unexpected error");
+        }
+    }
+
+    #[test]
+    fn test_filename_extraction() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("test.txt");
+        NATIVE_FS
+            .create_file(file_path.to_str().expect("getting str for file failed"))
+            .unwrap();
+        NativeFilestore::filename_from_full_path(file_path.to_str().unwrap());
+    }
+
+    #[test]
+    fn test_modular_checksum() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("mod-crc.bin");
+        fs::write(file_path.as_path(), EXAMPLE_DATA_CFDP).expect("writing test file failed");
+        // Kind of re-writing the modular checksum impl here which we are trying to test, but the
+        // numbers/correctness were verified manually using calculators, so this is okay.
+        let mut checksum: u32 = 0;
+        let mut buffer: [u8; 4] = [0; 4];
+        for i in 0..3 {
+            buffer = EXAMPLE_DATA_CFDP[i * 4..(i + 1) * 4].try_into().unwrap();
+            checksum = checksum.wrapping_add(u32::from_be_bytes(buffer));
+        }
+        buffer[0..3].copy_from_slice(&EXAMPLE_DATA_CFDP[12..15]);
+        buffer[3] = 0;
+        checksum = checksum.wrapping_add(u32::from_be_bytes(buffer));
+        let mut verif_buf: [u8; 32] = [0; 32];
+        let result = NATIVE_FS.checksum_verify(
+            file_path.to_str().unwrap(),
+            ChecksumType::Modular,
+            checksum,
+            &mut verif_buf,
+        );
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_null_checksum_impl() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("mod-crc.bin");
+        // The file to check does not even need to exist, and the verification buffer can be
+        // empty: the null checksum is always yields the same result.
+        let result = NATIVE_FS.checksum_verify(
+            file_path.to_str().unwrap(),
+            ChecksumType::NullChecksum,
+            0,
+            &mut [],
+        );
+        assert!(result.is_ok());
+        assert!(result.unwrap());
+    }
+
+    #[test]
+    fn test_checksum_not_implemented() {
+        let tmpdir = tempdir().expect("creating tmpdir failed");
+        let file_path = tmpdir.path().join("mod-crc.bin");
+        // The file to check does not even need to exist, and the verification buffer can be
+        // empty: the null checksum is always yields the same result.
+        let result = NATIVE_FS.checksum_verify(
+            file_path.to_str().unwrap(),
+            ChecksumType::Crc32Proximity1,
+            0,
+            &mut [],
+        );
+        assert!(result.is_err());
+        let error = result.unwrap_err();
+        if let FilestoreError::ChecksumTypeNotImplemented(cksum_type) = error {
+            assert_eq!(
+                error.to_string(),
+                format!("checksum {:?} not implemented", cksum_type)
+            );
+        } else {
+            panic!("unexpected error");
+        }
+    }
+}