std: xous: add support for path

Add support for the Xous-specific path implementation.

Signed-off-by: Sean Cross <sean@xobs.io>

Author: xobs

library/std/src/os/xous/mod.rs

@@ -7,6 +7,7 @@ pub mod ffi;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub mod services;
 
+pub mod path;
 /// A prelude for conveniently writing platform-specific code.
 ///
 /// Includes all extension traits, and some important type definitions.

library/std/src/os/xous/path.rs

@@ -0,0 +1,40 @@
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use crate::path;
+
+#[stable(feature = "file_type_ext", since = "1.5.0")]
+pub trait PathExt {
+    /// Returns `true` if this file type is a basis.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::os::xous::fs::FileTypeExt;
+    /// use std::io;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata(":.System")?;
+    ///     let file_type = meta.file_type();
+    ///     assert!(file_type.is_basis());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "file_type_ext", since = "1.5.0")]
+    fn is_basis(&self) -> bool;
+}
+
+#[stable(feature = "file_type_ext", since = "1.5.0")]
+impl PathExt for path::Path {
+    fn is_basis(&self) -> bool {
+        let Some(as_str) = self.as_os_str().to_str() else {
+             return false;
+        };
+
+        let Ok(path) = crate::sys::path::split_basis_dict_key(as_str) else {
+            return false;
+        };
+
+        path.basis.is_some() && path.dict.is_none() && path.key.is_none()
+    }
+}

library/std/src/sys/path/mod.rs

@@ -16,6 +16,10 @@ cfg_select! {
         mod uefi;
         pub use uefi::*;
     }
+    target_os = "xous" => {
+        mod xous;
+        pub use xous::*;
+    }
     target_os = "cygwin" => {
         mod cygwin;
         mod windows_prefix;

library/std/src/sys/path/xous.rs

@@ -0,0 +1,248 @@
+use crate::ffi::OsStr;
+use crate::io;
+use crate::path::{Path, PathBuf, Prefix};
+
+#[inline]
+pub fn is_sep_byte(b: u8) -> bool {
+    b == b'/' || b == b':'
+}
+
+#[inline]
+pub fn is_verbatim_sep(b: u8) -> bool {
+    b == b'/'
+}
+
+#[inline]
+pub fn parse_prefix(_: &OsStr) -> Option<Prefix<'_>> {
+    None
+}
+
+pub const HAS_PREFIXES: bool = false;
+pub const MAIN_SEP_STR: &str = "/";
+pub const MAIN_SEP: char = '/';
+pub const ALLOWED_SEP: &[char] = &['/', ':'];
+
+/// Make a POSIX path absolute without changing its semantics.
+pub(crate) fn absolute(path: &Path) -> io::Result<PathBuf> {
+    Ok(path.to_owned())
+}
+
+pub(crate) fn is_absolute(path: &Path) -> bool {
+    path.has_root() && path.prefix().is_some()
+}
+
+#[derive(Debug, PartialEq)]
+pub enum BasisSplitError {
+    /// This basis couldn't be split because it's the root element
+    Root,
+    /// This basis couldn't be split because it's listing all bases
+    All,
+    /// A path component was empty
+    EmptyComponent,
+}
+
+#[derive(Default, Debug, PartialEq)]
+pub struct SplitPath<'a> {
+    pub basis: Option<&'a str>,
+    pub dict: Option<&'a str>,
+    pub key: Option<&'a str>,
+}
+
+/// Split a path into its constituant Basis, Dict, and Key, if the path is legal.
+/// A Basis of `None` indicates the default Basis.
+pub fn split_basis_dict_key<'a>(src: &'a str) -> Result<SplitPath<'a>, BasisSplitError> {
+    let mut current_string = src;
+    let mut path = SplitPath::default();
+
+    // Special case for root
+    if src == ":" || src == "/" {
+        return Err(BasisSplitError::Root);
+    }
+    // Special case for listing all bases
+    if src == "::" || src == "//" || src == "/:" || src == ":/" {
+        return Err(BasisSplitError::All);
+    }
+
+    // If the string is an absolute path, then the first component is a basis
+    if let Some(src) = src.strip_prefix(ALLOWED_SEP) {
+        // See if we can split off a second separator which will get us the end
+        // of the Basis name
+        if let Some((maybe_basis, remainder)) = src.split_once(ALLOWED_SEP) {
+            // If the basis is empty, pull it from the default Basis function.
+            // Otherwise, use the specified basis.
+            if !maybe_basis.is_empty() {
+                path.basis = Some(maybe_basis);
+            }
+            current_string = remainder;
+        }
+    }
+
+    // Now that we have a fully-specified Basis, pull out the rest of the string.
+    if let Some(components) = current_string.rsplit_once(ALLOWED_SEP) {
+        let (mut dict, key) = components;
+        if let Some(stripped_dict) = dict.strip_prefix(ALLOWED_SEP) {
+            dict = stripped_dict;
+        }
+        // Don't allow empty dicts
+        if components.0.is_empty() {
+            return Err(BasisSplitError::EmptyComponent);
+        }
+        for path_component in dict.split(ALLOWED_SEP) {
+            if path_component.is_empty() {
+                return Err(BasisSplitError::EmptyComponent);
+            }
+        }
+
+        path.dict = Some(dict);
+        // Don't allow empty keys
+        if !key.is_empty() {
+            path.key = Some(key);
+        }
+    } else if !current_string.is_empty() {
+        path.dict = Some(current_string)
+    }
+
+    Ok(path)
+}
+
+#[cfg(test)]
+fn assert_basis_dict_key(test: &str, basis: Option<&str>, dict: Option<&str>, key: Option<&str>) {
+    let path = split_basis_dict_key(test).unwrap();
+    assert_eq!(path.basis, basis);
+    assert_eq!(path.dict, dict);
+    assert_eq!(path.key, key);
+}
+
+#[test]
+fn basis() {
+    // A basis named "Home Wifi"
+    assert_basis_dict_key(":Home Wifi:", Some("Home Wifi"), None, None);
+
+    // :.System: -- A basis named ".System"
+    assert_basis_dict_key(":.System:", Some(".System"), None, None);
+}
+
+#[test]
+fn dict() {
+    // wlan.networks -- A dict named "wlan.networks" in the default basis
+    assert_basis_dict_key("wlan.networks", None, Some("wlan.networks"), None);
+}
+
+#[test]
+fn key() {
+    // wlan.networks/recent -- A dict named "wlan.networks/recent", which may be considered a path, in the default basis. This also describes a key called "recent" in the dict "wlan.networks", depending on whether
+    assert_basis_dict_key("wlan.networks/recent", None, Some("wlan.networks"), Some("recent"));
+}
+
+#[test]
+fn key_legacy() {
+    // wlan.networks/recent -- A dict named "wlan.networks:recent", which may be considered a path, in the default basis. This also describes a key called "recent" in the dict "wlan.networks", depending on whether
+    assert_basis_dict_key("wlan.networks:recent", None, Some("wlan.networks"), Some("recent"));
+}
+
+#[test]
+fn dict_in_key() {
+    // :.System:wlan.networks -- A dict named "wlan.networks" in the basis ".System"
+    assert_basis_dict_key(":.System:wlan.networks", Some(".System"), Some("wlan.networks"), None);
+}
+
+#[test]
+fn basis_dict_key() {
+    // :.System:wlan.networks/recent -- a fully-qualified path, describing a key "recent" in the dict "wlan.networks" in the basis ".System".
+    assert_basis_dict_key(
+        ":.System:wlan.networks/recent",
+        Some(".System"),
+        Some("wlan.networks"),
+        Some("recent"),
+    );
+}
+
+#[test]
+fn basis_dict_key_legacy() {
+    // :.System:wlan.networks:recent -- a fully-qualified path, describing a key "recent" in the dict "wlan.networks" in the basis ".System".
+    assert_basis_dict_key(
+        ":.System:wlan.networks:recent",
+        Some(".System"),
+        Some("wlan.networks"),
+        Some("recent"),
+    );
+}
+
+#[test]
+fn root() {
+    // : -- The root, which lists every basis. Files cannot be created here. "Directories" can be created and destroyed, which corresponds to creating and destroying bases.
+    assert_eq!(split_basis_dict_key(":"), Err(BasisSplitError::Root));
+    assert_eq!(split_basis_dict_key("/"), Err(BasisSplitError::Root));
+}
+
+#[test]
+fn all_bases() {
+    // :: -- An empty basis is a synonym for all bases, so this corresponds to listing all dicts in the root of the default basis.
+    assert_eq!(split_basis_dict_key("::"), Err(BasisSplitError::All));
+    assert_eq!(split_basis_dict_key("/:"), Err(BasisSplitError::All));
+    assert_eq!(split_basis_dict_key(":/"), Err(BasisSplitError::All));
+    assert_eq!(split_basis_dict_key("//"), Err(BasisSplitError::All));
+}
+
+#[test]
+fn space_basis() {
+    // : : -- A basis named " ". Legal, but questionable
+    assert_basis_dict_key(": :", Some(" "), None, None);
+}
+
+#[test]
+fn space_dict() {
+    // -- A dict named " " in the default basis. Legal, but questionable.
+    assert_basis_dict_key(" ", None, Some(" "), None);
+}
+
+#[test]
+fn legacy_dict_key() {
+    // : -- A key named " " in a dict called " ". Legal.
+    assert_basis_dict_key(" : ", None, Some(" "), Some(" "));
+}
+
+#[test]
+fn legacy_trailing_separator() {
+    // baz: -- A dict named "baz" in the default basis with an extra ":" following. Legal.
+    assert_basis_dict_key("baz:", None, Some("baz"), None);
+}
+
+#[test]
+fn legacy_trailing_separator_two_dicts() {
+    // baz:foo: -- Currently illegal, but may become equal to baz:foo in the future.
+    assert_basis_dict_key("baz:foo:", None, Some("baz:foo"), None);
+}
+
+#[test]
+fn empty_dict() {
+    // ::: -- An key named ":" in an empty dict in the default basis. Illegal.
+    assert_eq!(split_basis_dict_key(":::"), Err(BasisSplitError::EmptyComponent));
+}
+
+#[test]
+fn empty_key_empty_dict() {
+    // :::: -- An key named "::" in an empty dict in the default basis. Illegal.
+    assert_eq!(split_basis_dict_key("::::"), Err(BasisSplitError::EmptyComponent));
+}
+
+#[test]
+fn key_in_default_basis() {
+    // ::foo -- A dict "foo" in the default basis.
+    assert_basis_dict_key("::foo", None, Some("foo"), None);
+}
+
+#[test]
+fn starts_with_slash() {
+    assert_basis_dict_key("/test/path", Some("test"), Some("path"), None);
+}
+
+#[test]
+fn non_legacy_basis() {
+    assert_basis_dict_key(
+        "/.System/wlan.networks/recent",
+        Some(".System"),
+        Some("wlan.networks"),
+        Some("recent"),
+    );
+}