src/librustc_span/caching_source_map_view.rs

   1 use crate::source_map::SourceMap;
   2 use crate::{BytePos, SourceFile};
   3 use rustc_data_structures::sync::Lrc;
   4
   5 #[derive(Clone)]
   6 struct CacheEntry {
   7     time_stamp: usize,
   8     line_number: usize,
   9     line_start: BytePos,
  10     line_end: BytePos,
  11     file: Lrc<SourceFile>,
  12     file_index: usize,
  13 }
  14
  15 #[derive(Clone)]
  16 pub struct CachingSourceMapView<'cm> {
  17     source_map: &'cm SourceMap,
  18     line_cache: [CacheEntry; 3],
  19     time_stamp: usize,
  20 }
  21
  22 impl<'cm> CachingSourceMapView<'cm> {
  23     pub fn new(source_map: &'cm SourceMap) -> CachingSourceMapView<'cm> {
  24         let files = source_map.files();
  25         let first_file = files[0].clone();
  26         let entry = CacheEntry {
  27             time_stamp: 0,
  28             line_number: 0,
  29             line_start: BytePos(0),
  30             line_end: BytePos(0),
  31             file: first_file,
  32             file_index: 0,
  33         };
  34
  35         CachingSourceMapView {
  36             source_map,
  37             line_cache: [entry.clone(), entry.clone(), entry],
  38             time_stamp: 0,
  39         }
  40     }
  41
  42     pub fn byte_pos_to_line_and_col(
  43         &mut self,
  44         pos: BytePos,
  45     ) -> Option<(Lrc<SourceFile>, usize, BytePos)> {
  46         self.time_stamp += 1;
  47
  48         // Check if the position is in one of the cached lines
  49         for cache_entry in self.line_cache.iter_mut() {
  50             if pos >= cache_entry.line_start && pos < cache_entry.line_end {
  51                 cache_entry.time_stamp = self.time_stamp;
  52
  53                 return Some((
  54                     cache_entry.file.clone(),
  55                     cache_entry.line_number,
  56                     pos - cache_entry.line_start,
  57                 ));
  58             }
  59         }
  60
  61         // No cache hit ...
  62         let mut oldest = 0;
  63         for index in 1..self.line_cache.len() {
  64             if self.line_cache[index].time_stamp < self.line_cache[oldest].time_stamp {
  65                 oldest = index;
  66             }
  67         }
  68
  69         let cache_entry = &mut self.line_cache[oldest];
  70
  71         // If the entry doesn't point to the correct file, fix it up
  72         if pos < cache_entry.file.start_pos || pos >= cache_entry.file.end_pos {
  73             let file_valid;
  74             if self.source_map.files().len() > 0 {
  75                 let file_index = self.source_map.lookup_source_file_idx(pos);
  76                 let file = self.source_map.files()[file_index].clone();
  77
  78                 if pos >= file.start_pos && pos < file.end_pos {
  79                     cache_entry.file = file;
  80                     cache_entry.file_index = file_index;
  81                     file_valid = true;
  82                 } else {
  83                     file_valid = false;
  84                 }
  85             } else {
  86                 file_valid = false;
  87             }
  88
  89             if !file_valid {
  90                 return None;
  91             }
  92         }
  93
  94         let line_index = cache_entry.file.lookup_line(pos).unwrap();
  95         let line_bounds = cache_entry.file.line_bounds(line_index);
  96
  97         cache_entry.line_number = line_index + 1;
  98         cache_entry.line_start = line_bounds.0;
  99         cache_entry.line_end = line_bounds.1;
 100         cache_entry.time_stamp = self.time_stamp;
 101
 102         return Some((
 103             cache_entry.file.clone(),
 104             cache_entry.line_number,
 105             pos - cache_entry.line_start,
 106         ));
 107     }
 108 }