readline: improve performance

benchmark/readline/readline-createInterface.js

@@ -0,0 +1,26 @@
+'use strict';
+const common = require('../common.js');
+const readline = require('readline');
+const { Readable, Writable } = require('stream');
+
+const bench = common.createBenchmark(main, {
+  n: [1e5],
+  terminal: [0, 1],
+});
+
+function main({ n, terminal }) {
+  bench.start();
+  for (let i = 0; i < n; i++) {
+    const input = new Readable({ read() {} });
+    const output = new Writable({ write(chunk, encoding, callback) {
+      callback();
+    } });
+    const rl = readline.createInterface({
+      input,
+      output,
+      terminal: Boolean(terminal),
+    });
+    rl.close();
+  }
+  bench.end(n);
+}

lib/internal/readline/interface.js

@@ -17,9 +17,10 @@ const {
   MathMax,
   MathMaxApply,
   NumberIsFinite,
-  ObjectDefineProperty,
+  ObjectDefineProperties,
   ObjectSetPrototypeOf,
   RegExpPrototypeExec,
+  RegExpPrototypeSymbolSplit,
   SafeStringIterator,
   StringPrototypeCodePointAt,
   StringPrototypeEndsWith,
@@ -172,6 +173,7 @@ function InterfaceConstructor(input, output, completer, terminal) {
   let crlfDelay;
   let prompt = '> ';
   let signal;
+  let historyOptions;
 
   if (input?.input) {
     // An options object was given
@@ -210,12 +212,15 @@ function InterfaceConstructor(input, output, completer, terminal) {
     crlfDelay = input.crlfDelay;
     input = input.input;
 
-    input.size = historySize;
-    input.history = history;
-    input.removeHistoryDuplicates = removeHistoryDuplicates;
+    historyOptions = {
+      __proto__: null,
+      size: historySize,
+      history,
+      removeHistoryDuplicates,
+    };
   }
 
-  this.setupHistoryManager(input);
+  this.setupHistoryManager(historyOptions ?? input);
 
   if (completer !== undefined && typeof completer !== 'function') {
     throw new ERR_INVALID_ARG_VALUE('completer', completer);
@@ -358,6 +363,30 @@ function InterfaceConstructor(input, output, completer, terminal) {
 ObjectSetPrototypeOf(InterfaceConstructor.prototype, EventEmitter.prototype);
 ObjectSetPrototypeOf(InterfaceConstructor, EventEmitter);
 
+// Shared descriptors for the history accessors defined on each instance.
+// Hoisted to avoid allocating fresh closures on every construction.
+const kHistoryAccessorDescriptors = {
+  __proto__: null,
+  history: {
+    __proto__: null, configurable: true, enumerable: true,
+    get() { return this.historyManager.history; },
+    set(newHistory) { return this.historyManager.history = newHistory; },
+  },
+  historyIndex: {
+    __proto__: null, configurable: true, enumerable: true,
+    get() { return this.historyManager.index; },
+    set(historyIndex) { return this.historyManager.index = historyIndex; },
+  },
+  historySize: {
+    __proto__: null, configurable: true, enumerable: true,
+    get() { return this.historyManager.size; },
+  },
+  isFlushing: {
+    __proto__: null, configurable: true, enumerable: true,
+    get() { return this.historyManager.isFlushing; },
+  },
+};
+
 class Interface extends InterfaceConstructor {
   get columns() {
     if (this.output?.columns) return this.output.columns;
@@ -388,27 +417,7 @@ class Interface extends InterfaceConstructor {
       this.historyManager.initialize(options.onHistoryFileLoaded);
     }
 
-    ObjectDefineProperty(this, 'history', {
-      __proto__: null, configurable: true, enumerable: true,
-      get() { return this.historyManager.history; },
-      set(newHistory) { return this.historyManager.history = newHistory; },
-    });
-
-    ObjectDefineProperty(this, 'historyIndex', {
-      __proto__: null, configurable: true, enumerable: true,
-      get() { return this.historyManager.index; },
-      set(historyIndex) { return this.historyManager.index = historyIndex; },
-    });
-
-    ObjectDefineProperty(this, 'historySize', {
-      __proto__: null, configurable: true, enumerable: true,
-      get() { return this.historyManager.size; },
-    });
-
-    ObjectDefineProperty(this, 'isFlushing', {
-      __proto__: null, configurable: true, enumerable: true,
-      get() { return this.historyManager.isFlushing; },
-    });
+    ObjectDefineProperties(this, kHistoryAccessorDescriptors);
   }
 
   [kSetRawMode](mode) {
@@ -622,37 +631,44 @@ class Interface extends InterfaceConstructor {
       this[kSawReturnAt] = 0;
     }
 
-    // Run test() on the new string chunk, not on the entire line buffer.
-    let newPartContainsEnding = RegExpPrototypeExec(lineEnding, string);
-    if (newPartContainsEnding !== null) {
-      if (this[kLine_buffer]) {
-        string = this[kLine_buffer] + string;
-        this[kLine_buffer] = null;
-        lineEnding.lastIndex = 0; // Start the search from the beginning of the string.
-        newPartContainsEnding = RegExpPrototypeExec(lineEnding, string);
-      }
-      this[kSawReturnAt] = StringPrototypeEndsWith(string, '\r') ?
-        DateNow() :
-        0;
-
-      const indexes = [0, newPartContainsEnding.index, lineEnding.lastIndex];
-      let nextMatch;
-      while ((nextMatch = RegExpPrototypeExec(lineEnding, string)) !== null) {
-        ArrayPrototypePush(indexes, nextMatch.index, lineEnding.lastIndex);
-      }
-      const lastIndex = indexes.length - 1;
-      // Either '' or (conceivably) the unfinished portion of the next line
-      this[kLine_buffer] = StringPrototypeSlice(string, indexes[lastIndex]);
-      for (let i = 1; i < lastIndex; i += 2) {
-        this[kOnLine](StringPrototypeSlice(string, indexes[i - 1], indexes[i]));
-      }
-    } else if (string) {
-      // No newlines this time, save what we have for next time
+    if (!string) {
+      return;
+    }
+
+    // Split the new string chunk, not the entire line buffer: a single
+    // split pass avoids allocating a match object per line ending.
+    // When the chunk contains none of the rare line endings, a plain
+    // string split is much cheaper than the regular expression.
+    const lines =
+      StringPrototypeIncludes(string, '\r') ||
+      StringPrototypeIncludes(string, '\u2028') ||
+      StringPrototypeIncludes(string, '\u2029') ?
+        RegExpPrototypeSymbolSplit(lineEnding, string) :
+        StringPrototypeSplit(string, '\n');
+    const lastIndex = lines.length - 1;
+    if (lastIndex === 0) {
+      // No line endings this time, save what we have for next time.
       if (this[kLine_buffer]) {
         this[kLine_buffer] += string;
       } else {
         this[kLine_buffer] = string;
       }
+      return;
+    }
+
+    this[kSawReturnAt] = StringPrototypeEndsWith(string, '\r') ?
+      DateNow() :
+      0;
+
+    let first = lines[0];
+    if (this[kLine_buffer]) {
+      first = this[kLine_buffer] + first;
+    }
+    // Either '' or (conceivably) the unfinished portion of the next line
+    this[kLine_buffer] = lines[lastIndex];
+    this[kOnLine](first);
+    for (let i = 1; i < lastIndex; i++) {
+      this[kOnLine](lines[i]);
     }
   }
 

lib/readline.js

@@ -115,7 +115,9 @@ function Interface(input, output, completer, terminal) {
   FunctionPrototypeCall(InterfaceConstructor, this,
                         input, output, completer, terminal);
 
-  if (process.env.TERM === 'dumb') {
+  // Reading process.env is expensive and _ttyWrite is only used in
+  // terminal mode, so only check for a dumb terminal when relevant.
+  if (this.terminal && process.env.TERM === 'dumb') {
     this._ttyWrite = FunctionPrototypeBind(_ttyWriteDumb, this);
   }
 }