perf: WithIndices (#150)

src/decoder.rs

@@ -39,7 +39,6 @@ pub(crate) struct MappingsDecoder<'a> {
   current_value: i64,
   current_value_pos: usize,
   generated_line: u32,
-  generated_column: i64,
 }
 
 impl<'a> MappingsDecoder<'a> {
@@ -52,7 +51,6 @@ impl<'a> MappingsDecoder<'a> {
       current_value: 0,
       current_value_pos: 0,
       generated_line: 1,
-      generated_column: -1,
     }
   }
 }
@@ -67,44 +65,39 @@ impl Iterator for MappingsDecoder<'_> {
         continue;
       }
       if (value & COM) != 0 {
-        let mapping = match self.current_data_pos {
-          1 => Some(Mapping {
-            generated_line: self.generated_line,
-            generated_column: self.current_data[0],
-            original: None,
-          }),
-          4 => Some(Mapping {
-            generated_line: self.generated_line,
-            generated_column: self.current_data[0],
-            original: Some(OriginalLocation {
+        let mut mapping = Mapping {
+          generated_line: self.generated_line,
+          generated_column: self.current_data[0],
+          original: None,
+        };
+        let current_data_pos = self.current_data_pos;
+        self.current_data_pos = 0;
+        if value == SEM {
+          self.generated_line += 1;
+          self.current_data[0] = 0;
+        }
+        match current_data_pos {
+          1 => return Some(mapping),
+          4 => {
+            mapping.original = Some(OriginalLocation {
               source_index: self.current_data[1],
               original_line: self.current_data[2],
               original_column: self.current_data[3],
               name_index: None,
-            }),
-          }),
-          5 => Some(Mapping {
-            generated_line: self.generated_line,
-            generated_column: self.current_data[0],
-            original: Some(OriginalLocation {
+            });
+            return Some(mapping);
+          }
+          5 => {
+            mapping.original = Some(OriginalLocation {
               source_index: self.current_data[1],
               original_line: self.current_data[2],
               original_column: self.current_data[3],
               name_index: Some(self.current_data[4]),
-            }),
-          }),
-          _ => None,
+            });
+            return Some(mapping);
+          }
+          _ => (),
         };
-        self.generated_column = self.current_data[0] as i64;
-        self.current_data_pos = 0;
-        if value == SEM {
-          self.generated_line += 1;
-          self.current_data[0] = 0;
-          self.generated_column = -1;
-        }
-        if mapping.is_some() {
-          return mapping;
-        }
       } else if (value & CONTINUATION_BIT) == 0 {
         // last sextet
         self.current_value |= (value as i64) << self.current_value_pos;

src/helpers.rs

@@ -1252,7 +1252,7 @@ pub trait SourceText<'a>: Default + Clone + ToString {
   fn ends_with(&self, value: &str) -> bool;
 
   /// Returns an iterator over the char indices in the text.
-  fn char_indices(&self) -> impl Iterator<Item = (usize, char)>;
+  fn char_indices(&self) -> impl DoubleEndedIterator<Item = (usize, char)>;
 
   /// Gets the byte at the specified index, if it exists.
   fn get_byte(&self, byte_index: usize) -> Option<u8>;
@@ -1289,7 +1289,7 @@ impl<'a> SourceText<'a> for Rope<'a> {
     (*self).ends_with(value)
   }
 
-  fn char_indices(&self) -> impl Iterator<Item = (usize, char)> {
+  fn char_indices(&self) -> impl DoubleEndedIterator<Item = (usize, char)> {
     self.char_indices()
   }
 
@@ -1331,7 +1331,7 @@ impl<'a> SourceText<'a> for &'a str {
     (*self).ends_with(value)
   }
 
-  fn char_indices(&self) -> impl Iterator<Item = (usize, char)> {
+  fn char_indices(&self) -> impl DoubleEndedIterator<Item = (usize, char)> {
     (*self).char_indices()
   }
 

src/rope.rs

@@ -2,7 +2,6 @@
 
 use std::{
   borrow::Cow,
-  collections::VecDeque,
   hash::Hash,
   ops::{Bound, RangeBounds},
   rc::Rc,
@@ -134,13 +133,24 @@ impl<'a> Rope<'a> {
           iter: s.char_indices(),
         },
       },
-      Repr::Full(data) => CharIndices {
-        iter: CharIndicesEnum::Full {
-          chunks: data,
-          char_indices: VecDeque::new(),
-          chunk_index: 0,
-        },
-      },
+      Repr::Full(vec) => {
+        let right_byte_offset = vec.iter().map(|(s, _)| s.len() as u32).sum();
+
+        CharIndices {
+          iter: CharIndicesEnum::Full {
+            iters: vec
+              .iter()
+              .map(|(s, _)| s.char_indices())
+              .collect::<Vec<_>>(),
+            left_chunk_index: 0,
+            left_byte_offset: 0,
+            last_left_indice: None,
+            right_chunk_index: (vec.len() - 1) as u32,
+            right_byte_offset,
+            right_byte_offset_for: vec.len() as u32,
+          },
+        }
+      }
     }
   }
 
@@ -658,9 +668,13 @@ enum CharIndicesEnum<'a, 'b> {
     iter: std::str::CharIndices<'b>,
   },
   Full {
-    chunks: &'a [(&'b str, usize)],
-    char_indices: VecDeque<(usize, char)>,
-    chunk_index: usize,
+    iters: Vec<std::str::CharIndices<'a>>,
+    left_chunk_index: u32,
+    left_byte_offset: u32,
+    last_left_indice: Option<(usize, char)>,
+    right_chunk_index: u32,
+    right_byte_offset: u32,
+    right_byte_offset_for: u32,
   },
 }
 
@@ -675,29 +689,59 @@ impl Iterator for CharIndices<'_, '_> {
     match &mut self.iter {
       CharIndicesEnum::Light { iter } => iter.next(),
       CharIndicesEnum::Full {
-        chunks,
-        char_indices,
-        chunk_index,
+        iters,
+        left_chunk_index,
+        left_byte_offset,
+        last_left_indice,
+        ..
       } => {
-        if let Some(item) = char_indices.pop_front() {
-          return Some(item);
-        }
-
-        if *chunk_index >= chunks.len() {
+        if (*left_chunk_index as usize) >= iters.len() {
           return None;
         }
-
-        // skip empty chunks
-        while *chunk_index < chunks.len() && chunks[*chunk_index].0.is_empty() {
-          *chunk_index += 1;
+        if let Some((byte_index, char)) =
+          iters[*left_chunk_index as usize].next()
+        {
+          *last_left_indice = Some((byte_index, char));
+          Some((byte_index + (*left_byte_offset as usize), char))
+        } else {
+          *left_chunk_index += 1;
+          if let Some((byte_index, char)) = last_left_indice.take() {
+            *left_byte_offset =
+              *left_byte_offset + byte_index as u32 + char.len_utf8() as u32;
+          }
+          self.next()
         }
+      }
+    }
+  }
+}
 
-        let (chunk, start_pos) = chunks[*chunk_index];
-
-        char_indices
-          .extend(chunk.char_indices().map(|(i, c)| (start_pos + i, c)));
-        *chunk_index += 1;
-        char_indices.pop_front()
+impl DoubleEndedIterator for CharIndices<'_, '_> {
+  fn next_back(&mut self) -> Option<Self::Item> {
+    match &mut self.iter {
+      CharIndicesEnum::Light { iter } => iter.next_back(),
+      CharIndicesEnum::Full {
+        iters,
+        right_chunk_index,
+        right_byte_offset,
+        right_byte_offset_for,
+        ..
+      } => {
+        if let Some((byte_index, char)) =
+          iters[*right_chunk_index as usize].next_back()
+        {
+          if *right_byte_offset_for != *right_chunk_index {
+            *right_byte_offset =
+              *right_byte_offset - byte_index as u32 - char.len_utf8() as u32;
+            *right_byte_offset_for = *right_chunk_index;
+          }
+          Some((byte_index + (*right_byte_offset as usize), char))
+        } else if *right_chunk_index > 0 {
+          *right_chunk_index -= 1;
+          self.next_back()
+        } else {
+          None
+        }
       }
     }
   }
@@ -1168,6 +1212,29 @@ mod tests {
     );
   }
 
+  #[test]
+  fn reverse_char_indices() {
+    let mut a = Rope::new();
+    a.add("abc");
+    a.add("def");
+    assert_eq!(
+      a.char_indices().rev().collect::<Vec<_>>(),
+      "abcdef".char_indices().rev().collect::<Vec<_>>()
+    );
+
+    let mut a = Rope::new();
+    a.add("こんにちは");
+    assert_eq!(
+      a.char_indices().rev().collect::<Vec<_>>(),
+      "こんにちは".char_indices().rev().collect::<Vec<_>>()
+    );
+    a.add("世界");
+    assert_eq!(
+      a.char_indices().rev().collect::<Vec<_>>(),
+      "こんにちは世界".char_indices().rev().collect::<Vec<_>>()
+    );
+  }
+
   #[test]
   fn lines1() {
     let rope = Rope::from("abc");