perf: cache decode mappings (#97)

* feat: cache decode_mappings

* feat: reduce memory call

Author: SyMind

src/concat_source.rs

@@ -161,12 +161,16 @@ impl StreamChunks for ConcatSource {
     let mut current_column_offset = 0;
     let mut source_mapping: HashMap<String, u32> = HashMap::default();
     let mut name_mapping: HashMap<String, u32> = HashMap::default();
-    let mut need_to_cloas_mapping = false;
+    let mut need_to_close_mapping = false;
+
+    let source_index_mapping: RefCell<HashMap<u32, u32>> =
+      RefCell::new(HashMap::default());
+    let name_index_mapping: RefCell<HashMap<u32, u32>> =
+      RefCell::new(HashMap::default());
+
     for item in self.children() {
-      let source_index_mapping: RefCell<HashMap<u32, u32>> =
-        RefCell::new(HashMap::default());
-      let name_index_mapping: RefCell<HashMap<u32, u32>> =
-        RefCell::new(HashMap::default());
+      source_index_mapping.borrow_mut().clear();
+      name_index_mapping.borrow_mut().clear();
       let mut last_mapping_line = 0;
       let GeneratedInfo {
         generated_line,
@@ -180,7 +184,7 @@ impl StreamChunks for ConcatSource {
           } else {
             mapping.generated_column
           };
-          if need_to_cloas_mapping {
+          if need_to_close_mapping {
             if mapping.generated_line != 1 || mapping.generated_column != 0 {
               on_chunk(
                 None,
@@ -191,7 +195,7 @@ impl StreamChunks for ConcatSource {
                 },
               );
             }
-            need_to_cloas_mapping = false;
+            need_to_close_mapping = false;
           }
           let result_source_index =
             mapping.original.as_ref().and_then(|original| {
@@ -282,7 +286,7 @@ impl StreamChunks for ConcatSource {
             .insert(i, global_index.unwrap());
         },
       );
-      if need_to_cloas_mapping && (generated_line != 1 || generated_column != 0)
+      if need_to_close_mapping && (generated_line != 1 || generated_column != 0)
       {
         on_chunk(
           None,
@@ -292,14 +296,14 @@ impl StreamChunks for ConcatSource {
             original: None,
           },
         );
-        need_to_cloas_mapping = false;
+        need_to_close_mapping = false;
       }
       if generated_line > 1 {
         current_column_offset = generated_column;
       } else {
         current_column_offset += generated_column;
       }
-      need_to_cloas_mapping = need_to_cloas_mapping
+      need_to_close_mapping = need_to_close_mapping
         || (options.final_source && last_mapping_line == generated_line);
       current_line_offset += generated_line - 1;
     }

src/source.rs

@@ -4,7 +4,7 @@ use std::{
   convert::{TryFrom, TryInto},
   fmt,
   hash::{Hash, Hasher},
-  sync::Arc,
+  sync::{Arc, OnceLock},
 };
 
 use dyn_clone::DynClone;
@@ -179,14 +179,26 @@ impl MapOptions {
 }
 
 /// The source map created by [Source::map].
-#[derive(Debug, Clone, Default, PartialEq, Eq, Hash)]
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
 pub struct SourceMap {
   file: Option<String>,
   mappings: String,
   sources: Vec<Cow<'static, str>>,
   sources_content: Vec<Cow<'static, str>>,
   names: Vec<Cow<'static, str>>,
   source_root: Option<String>,
+  decoded_mappings: OnceLock<Vec<Mapping>>,
+}
+
+impl Hash for SourceMap {
+  fn hash<H: Hasher>(&self, state: &mut H) {
+    self.file.hash(state);
+    self.mappings.hash(state);
+    self.sources.hash(state);
+    self.sources_content.hash(state);
+    self.names.hash(state);
+    self.source_root.hash(state);
+  }
 }
 
 impl SourceMap {
@@ -205,6 +217,7 @@ impl SourceMap {
       sources_content,
       names,
       source_root: None,
+      decoded_mappings: Default::default(),
     }
   }
 
@@ -220,7 +233,11 @@ impl SourceMap {
 
   /// Get the decoded mappings in [SourceMap].
   pub fn decoded_mappings(&'_ self) -> impl IntoIterator<Item = Mapping> + '_ {
-    decode_mappings(self)
+    self
+      .decoded_mappings
+      .get_or_init(|| decode_mappings(self).collect::<Vec<_>>())
+      .clone()
+      .into_iter()
   }
 
   /// Get the mappings string in [SourceMap].
@@ -412,6 +429,7 @@ impl TryFrom<RawSourceMap> for SourceMap {
       sources_content,
       names,
       source_root: raw.source_root,
+      decoded_mappings: Default::default(),
     })
   }
 }