Make replace a rustfix module

Author: killercup

Cargo.toml

@@ -29,6 +29,7 @@ env_logger = "0.5.0-rc.1"
 log = "0.4.1"
 pretty_assertions = "0.4.1"
 tempdir = "0.3.5"
+proptest = "0.7.0"
 
 [workspace]
 members = [

src/lib.rs

@@ -1,8 +1,11 @@
 #[macro_use]
 extern crate serde_derive;
 extern crate serde_json;
+#[macro_use]
 extern crate failure;
-extern crate replace_rs as replace;
+#[cfg(test)]
+#[macro_use]
+extern crate proptest;
 
 use std::collections::HashSet;
 use std::ops::Range;
@@ -11,6 +14,7 @@ use failure::Error;
 
 pub mod diagnostics;
 use diagnostics::{Diagnostic, DiagnosticSpan};
+mod replace;
 
 pub fn get_suggestions_from_json<S: ::std::hash::BuildHasher>(
     input: &str,

src/replace.rs

@@ -0,0 +1,223 @@
+//! A small module giving you a simple container that allows easy and cheap
+//! replacement of parts of its content, with the ability to prevent changing
+//! the same parts multiple times.
+
+use std::rc::Rc;
+use failure::Error;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+enum State {
+    Initial,
+    Replaced(Rc<[u8]>),
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Span {
+    /// Start of this span in parent data
+    start: usize,
+    /// up to end inculding
+    end: usize,
+    data: State,
+}
+
+/// A container that allows easily replacing chunks of its data
+#[derive(Debug, Clone, Default)]
+pub struct Data {
+    original: Vec<u8>,
+    parts: Vec<Span>,
+}
+
+impl Data {
+    /// Create a new data container from a slice of bytes
+    pub fn new(data: &[u8]) -> Self {
+        Data {
+            original: data.into(),
+            parts: vec![Span {
+                data: State::Initial,
+                start: 0,
+                end: data.len(),
+            }],
+        }
+    }
+
+    /// Render this data as a vector of bytes
+    pub fn to_vec(&self) -> Vec<u8> {
+        self.parts.iter().fold(Vec::new(), |mut acc, d| {
+            match d.data {
+                State::Initial => acc.extend_from_slice(&self.original[d.start..d.end]),
+                State::Replaced(ref d) => acc.extend_from_slice(&d),
+            };
+            acc
+        })
+    }
+
+    /// Replace a chunk of data with the given slice, erroring when this part
+    /// was already changed previously.
+    pub fn replace_range(
+        &mut self,
+        from: usize,
+        up_to_and_including: usize,
+        data: &[u8],
+    ) -> Result<(), Error> {
+        ensure!(
+            from <= up_to_and_including,
+            "Invalid range {}...{}, start is larger than end",
+            from,
+            up_to_and_including
+        );
+        ensure!(
+            up_to_and_including <= self.original.len(),
+            "Invalid range {}...{} given, original data is only {} byte long",
+            from,
+            up_to_and_including,
+            self.original.len()
+        );
+
+        // Since we error out when replacing an already replaced chunk of data,
+        // we can take some shortcuts here. For example, there can be no
+        // overlapping replacements -- we _always_ split a chunk of 'initial'
+        // data into three[^empty] parts, and there can't ever be two 'initial'
+        // parts touching.
+        //
+        // [^empty]: Leading and trailing ones might be empty if we replace
+        // the whole chunk. As an optimization and without loss of generality we
+        // don't add empty parts.
+        let new_parts = {
+            let index_of_part_to_split = self.parts
+                .iter()
+                .position(|p| p.start <= from && p.end >= up_to_and_including)
+                .ok_or_else(|| {
+                    format_err!(
+                        "Could not find data slice that covers range {}..{}",
+                        from,
+                        up_to_and_including
+                    )
+                })?;
+
+            let part_to_split = &self.parts[index_of_part_to_split];
+            ensure!(
+                part_to_split.data == State::Initial,
+                "Cannot replace slice of data that was already replaced"
+            );
+
+            let mut new_parts = Vec::with_capacity(self.parts.len() + 2);
+
+            // Previous parts
+            if let Some(ps) = self.parts.get(..index_of_part_to_split) {
+                new_parts.extend_from_slice(&ps);
+            }
+
+            // Keep initial data on left side of part
+            if from > part_to_split.start {
+                new_parts.push(Span {
+                    start: part_to_split.start,
+                    end: from,
+                    data: State::Initial,
+                });
+            }
+
+            // New part
+            new_parts.push(Span {
+                start: from,
+                end: up_to_and_including,
+                data: State::Replaced(data.into()),
+            });
+
+            // Keep initial data on right side of part
+            if up_to_and_including < part_to_split.end {
+                new_parts.push(Span {
+                    start: up_to_and_including + 1,
+                    end: part_to_split.end,
+                    data: State::Initial,
+                });
+            }
+
+            // Following parts
+            if let Some(ps) = self.parts.get(index_of_part_to_split + 1..) {
+                new_parts.extend_from_slice(&ps);
+            }
+
+            new_parts
+        };
+
+        self.parts = new_parts;
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use proptest::prelude::*;
+
+    fn str(i: &[u8]) -> &str {
+        ::std::str::from_utf8(i).unwrap()
+    }
+
+    #[test]
+    fn replace_some_stuff() {
+        let mut d = Data::new(b"foo bar baz");
+        d.replace_range(4, 6, b"lol").unwrap();
+        assert_eq!("foo lol baz", str(&d.to_vec()));
+    }
+
+    #[test]
+    fn replace_a_single_char() {
+        let mut d = Data::new(b"let y = true;");
+        d.replace_range(4, 4, b"mut y").unwrap();
+        assert_eq!("let mut y = true;", str(&d.to_vec()));
+    }
+
+    #[test]
+    fn replace_multiple_lines() {
+        let mut d = Data::new(b"lorem\nipsum\ndolor");
+
+        d.replace_range(6, 10, b"lol").unwrap();
+        assert_eq!("lorem\nlol\ndolor", str(&d.to_vec()));
+
+        d.replace_range(12, 17, b"lol").unwrap();
+        assert_eq!("lorem\nlol\nlol", str(&d.to_vec()));
+    }
+
+    #[test]
+    #[should_panic(expected = "Cannot replace slice of data that was already replaced")]
+    fn replace_overlapping_stuff_errs() {
+        let mut d = Data::new(b"foo bar baz");
+
+        d.replace_range(4, 6, b"lol").unwrap();
+        assert_eq!("foo lol baz", str(&d.to_vec()));
+
+        d.replace_range(4, 6, b"lol").unwrap();
+    }
+
+    #[test]
+    #[should_panic(expected = "original data is only 3 byte long")]
+    fn broken_replacements() {
+        let mut d = Data::new(b"foo");
+        d.replace_range(4, 7, b"lol").unwrap();
+    }
+
+    proptest! {
+        #[test]
+        #[ignore]
+        fn new_to_vec_roundtrip(ref s in "\\PC*") {
+            assert_eq!(s.as_bytes(), Data::new(s.as_bytes()).to_vec().as_slice());
+        }
+
+        #[test]
+        #[ignore]
+        fn replace_random_chunks(
+            ref data in "\\PC*",
+            ref replacements in prop::collection::vec(
+                (any::<::std::ops::Range<usize>>(), any::<Vec<u8>>()),
+                1..1337,
+            )
+        ) {
+            let mut d = Data::new(data.as_bytes());
+            for &(ref range, ref bytes) in replacements {
+                let _ = d.replace_range(range.start, range.end, bytes);
+            }
+        }
+    }
+}