Mercurial > core / rust/lib/sxp/src/iter.rs

 //! iter.rs --- SXP Iterator primitives
 use crate::io;
 
 pub struct LineColIterator<I> {
   iter: I,
 
   /// Index of the current line. Characters in the first line of the input
   /// (before the first newline character) are in line 1.
   line: usize,
 
   /// Index of the current column. The first character in the input and any
   /// characters immediately following a newline character are in column 1.
   /// The column is 0 immediately after a newline character has been read.
   col: usize,
 
   /// Byte offset of the start of the current line. This is the sum of lengths
   /// of all previous lines. Keeping track of things this way allows efficient
   /// computation of the current line, column, and byte offset while only
   /// updating one of the counters in `next()` in the common case.
   start_of_line: usize,
 }
 
 impl<I> LineColIterator<I>
 where
   I: Iterator<Item = io::Result<u8>>,
 {
   pub fn new(iter: I) -> LineColIterator<I> {
     LineColIterator {
       iter,
       line: 1,
       col: 0,
       start_of_line: 0,
     }
   }
 
   pub fn line(&self) -> usize {
     self.line
   }
 
   pub fn col(&self) -> usize {
     self.col
   }
 
   pub fn byte_offset(&self) -> usize {
     self.start_of_line + self.col
   }
 }
 
 impl<I> Iterator for LineColIterator<I>
 where
   I: Iterator<Item = io::Result<u8>>,
 {
   type Item = io::Result<u8>;
 
   fn next(&mut self) -> Option<io::Result<u8>> {
     match self.iter.next() {
       None => None,
       Some(Ok(b'\n')) => {
         self.start_of_line += self.col + 1;
         self.line += 1;
         self.col = 0;
         Some(Ok(b'\n'))
       }
       Some(Ok(c)) => {
         self.col += 1;
         Some(Ok(c))
       }
       Some(Err(e)) => Some(Err(e)),
     }
   }
 }