src/libsyntax_pos/caching_source_map_view.rs

   1 use rustc_data_structures::sync::Lrc;
   2 use crate::source_map::SourceMap;
   3 use crate::{BytePos, SourceFile};
   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(&mut self,
  43                                     pos: BytePos)
  44                                     -> Option<(Lrc<SourceFile>, usize, BytePos)> {
  45         self.time_stamp += 1;
  46
  47         // Check if the position is in one of the cached lines
  48         for cache_entry in self.line_cache.iter_mut() {
  49             if pos >= cache_entry.line_start && pos < cache_entry.line_end {
  50                 cache_entry.time_stamp = self.time_stamp;
  51
  52                 return Some((cache_entry.file.clone(),
  53                              cache_entry.line_number,
  54                              pos - cache_entry.line_start));
  55             }
  56         }
  57
  58         // No cache hit ...
  59         let mut oldest = 0;
  60         for index in 1 .. self.line_cache.len() {
  61             if self.line_cache[index].time_stamp < self.line_cache[oldest].time_stamp {
  62                 oldest = index;
  63             }
  64         }
  65
  66         let cache_entry = &mut self.line_cache[oldest];
  67
  68         // If the entry doesn't point to the correct file, fix it up
  69         if pos < cache_entry.file.start_pos || pos >= cache_entry.file.end_pos {
  70             let file_valid;
  71             if self.source_map.files().len() > 0 {
  72                 let file_index = self.source_map.lookup_source_file_idx(pos);
  73                 let file = self.source_map.files()[file_index].clone();
  74
  75                 if pos >= file.start_pos && pos < file.end_pos {
  76                     cache_entry.file = file;
  77                     cache_entry.file_index = file_index;
  78                     file_valid = true;
  79                 } else {
  80                     file_valid = false;
  81                 }
  82             } else {
  83                 file_valid = false;
  84             }
  85
  86             if !file_valid {
  87                 return None;
  88             }
  89         }
  90
  91         let line_index = cache_entry.file.lookup_line(pos).unwrap();
  92         let line_bounds = cache_entry.file.line_bounds(line_index);
  93
  94         cache_entry.line_number = line_index + 1;
  95         cache_entry.line_start = line_bounds.0;
  96         cache_entry.line_end = line_bounds.1;
  97         cache_entry.time_stamp = self.time_stamp;
  98
  99         return Some((cache_entry.file.clone(),
 100                      cache_entry.line_number,
 101                      pos - cache_entry.line_start));
 102     }
 103 }