Use array instead of map

Author: szuend

bench/decode.bench.ts

@@ -9,7 +9,9 @@ import { decode, DecodeMode } from "../mod.ts";
 
 const BENCHMARKS = await (async () => {
   const result = [];
-  for await (const file of expandGlob("*.js.map", { root: import.meta.dirname })) {
+  for await (
+    const file of expandGlob("*.js.map", { root: import.meta.dirname })
+  ) {
     const mapContent = Deno.readTextFileSync(file.path);
     const mapJson = JSON.parse(mapContent);
     result.push({
@@ -21,7 +23,7 @@ const BENCHMARKS = await (async () => {
   return result;
 })();
 
-for (const {name, mapJson, size} of BENCHMARKS) {
+for (const { name, mapJson, size } of BENCHMARKS) {
   Deno.bench(`${name}, lax, ${format(size)}`, () => {
     decode(mapJson, { mode: DecodeMode.LOOSE });
   });

deno.lock

@@ -76,8 +76,7 @@ class Decoder {
   readonly #scopeStack: OriginalScope[] = [];
   readonly #rangeStack: GeneratedRange[] = [];
 
-  readonly #countToScope = new Map<number, OriginalScope>();
-  #scopeCounter = 0;
+  #flatOriginalScopes: OriginalScope[] = [];
 
   constructor(scopes: string, names: string[], options?: { mode: DecodeMode }) {
     this.#encodedScopes = scopes;
@@ -117,7 +116,7 @@ class Decoder {
           );
 
           this.#scopeStack.push(scope);
-          this.#countToScope.set(this.#scopeCounter++, scope);
+          this.#flatOriginalScopes.push(scope);
           break;
         }
         case Tag.ORIGINAL_SCOPE_VARIABLES: {
@@ -187,9 +186,8 @@ class Decoder {
 
           if (item.definitionIdx !== undefined) {
             this.#rangeState.defScopeIdx += item.definitionIdx;
-            range.originalScope = this.#countToScope.get(
-              this.#rangeState.defScopeIdx,
-            );
+            range.originalScope =
+              this.#flatOriginalScopes[this.#rangeState.defScopeIdx];
             // TODO: Maybe throw if the idx is invalid?
           }
 
@@ -265,8 +263,7 @@ class Decoder {
 
     this.#scopes = [];
     this.#ranges = [];
-    this.#scopeCounter = 0;
-    this.#countToScope.clear();
+    this.#flatOriginalScopes = [];
 
     return info;
   }