crate::path::Path improvements

Author: Kinrany

src/path/mod.rs

@@ -17,7 +17,6 @@
 
 //! Path abstraction for Object Storage
 
-use itertools::Itertools;
 use percent_encoding::percent_decode;
 use std::fmt::Formatter;
 #[cfg(not(target_arch = "wasm32"))]
@@ -29,9 +28,12 @@ pub const DELIMITER: &str = "/";
 /// The path delimiter as a single byte
 pub const DELIMITER_BYTE: u8 = DELIMITER.as_bytes()[0];
 
+/// The path delimiter as a single char
+pub const DELIMITER_CHAR: char = DELIMITER_BYTE as char;
+
 mod parts;
 
-pub use parts::{InvalidPart, PathPart};
+pub use parts::{InvalidPart, PathPart, PathParts};
 
 /// Error returned by [`Path::parse`]
 #[derive(Debug, thiserror::Error)]
@@ -157,6 +159,18 @@ pub struct Path {
 }
 
 impl Path {
+    /// An empty [`Path`] that points to the root of the store, equivalent to `Path::from("/")`.
+    ///
+    /// See also [`Path::is_root`].
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use object_store::path::Path;
+    /// assert_eq!(Path::ROOT, Path::from("/"));
+    /// ```
+    pub const ROOT: Self = Self { raw: String::new() };
+
     /// Parse a string as a [`Path`], returning a [`Error`] if invalid,
     /// as defined on the docstring for [`Path`]
     ///
@@ -255,14 +269,53 @@ impl Path {
         Self::parse(decoded)
     }
 
-    /// Returns the [`PathPart`] of this [`Path`]
-    pub fn parts(&self) -> impl Iterator<Item = PathPart<'_>> {
-        self.raw
-            .split_terminator(DELIMITER)
-            .map(|s| PathPart { raw: s.into() })
+    /// Returns the number of [`PathPart`]s in this [`Path`]
+    ///
+    /// This is equivalent to calling `.parts().count()` manually.
+    ///
+    /// # Performance
+    ///
+    /// This operation is `O(n)`.
+    #[doc(alias = "len")]
+    pub fn parts_count(&self) -> usize {
+        self.raw.split_terminator(DELIMITER).count()
+    }
+
+    /// True if this [`Path`] points to the root of the store, equivalent to `Path::from("/")`.
+    ///
+    /// See also [`Path::root`].
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use object_store::path::Path;
+    /// assert!(Path::from("/").is_root());
+    /// assert!(Path::parse("").unwrap().is_root());
+    /// ```
+    pub fn is_root(&self) -> bool {
+        self.raw.is_empty()
+    }
+
+    /// Returns the [`PathPart`]s of this [`Path`]
+    pub fn parts(&self) -> PathParts<'_> {
+        PathParts::new(self)
+    }
+
+    /// Returns a copy of this [`Path`] with the last path segment removed
+    ///
+    /// Returns `None` if this path has zero segments.
+    #[doc(alias = "folder")]
+    pub fn prefix(&self) -> Option<Self> {
+        let prefix = self.raw.rsplit_once(DELIMITER)?.0;
+
+        Some(Self {
+            raw: prefix.to_string(),
+        })
     }
 
     /// Returns the last path segment containing the filename stored in this [`Path`]
+    ///
+    /// Returns `None` only if this path is the root path.
     pub fn filename(&self) -> Option<&str> {
         match self.raw.is_empty() {
             true => None,
@@ -348,13 +401,22 @@ where
     I: Into<PathPart<'a>>,
 {
     fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self {
-        let raw = T::into_iter(iter)
-            .map(|s| s.into())
-            .filter(|s| !s.raw.is_empty())
-            .map(|s| s.raw)
-            .join(DELIMITER);
+        let mut this = Self::ROOT;
+        this.extend(iter);
+        this
+    }
+}
 
-        Self { raw }
+impl<'a, I: Into<PathPart<'a>>> Extend<I> for Path {
+    fn extend<T: IntoIterator<Item = I>>(&mut self, iter: T) {
+        for s in iter.into_iter() {
+            let s = s.into();
+            if s.raw.is_empty() {
+                continue;
+            }
+            self.raw.push(DELIMITER_CHAR);
+            self.raw.push_str(&s.raw);
+        }
     }
 }
 

src/path/parts.rs

@@ -16,7 +16,11 @@
 // under the License.
 
 use percent_encoding::{AsciiSet, CONTROLS, percent_encode};
-use std::borrow::Cow;
+use std::{
+    borrow::Cow,
+    iter::{self, FusedIterator},
+    str::SplitTerminator,
+};
 
 use crate::path::DELIMITER_BYTE;
 
@@ -131,6 +135,37 @@ impl AsRef<str> for PathPart<'_> {
     }
 }
 
+/// See [`Path::parts`](super::Path::parts)
+#[derive(Debug, Clone)]
+pub struct PathParts<'a>(iter::Map<SplitTerminator<'a, char>, fn(&str) -> PathPart<'_>>);
+
+impl<'a> PathParts<'a> {
+    /// Create an iterator over the parts of the provided [`Path`]
+    pub(super) fn new(path: &'a super::Path) -> Self {
+        Self(
+            path.raw
+                .split_terminator(super::DELIMITER_CHAR)
+                .map(|s| PathPart { raw: s.into() }),
+        )
+    }
+}
+
+impl<'a> Iterator for PathParts<'a> {
+    type Item = PathPart<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next()
+    }
+}
+
+impl<'a> FusedIterator for PathParts<'a> {}
+
+impl<'a> DoubleEndedIterator for PathParts<'a> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.0.next_back()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;