string_decoder: lazy loaded

PR-URL: #20567
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

Author: BridgeAR

lib/_stream_readable.js

@@ -40,7 +40,9 @@ const {
 }=require('internal/errors').codes;
 constReadableAsyncIterator=require('internal/streams/async_iterator');
 const{ emitExperimentalWarning }=require('internal/util');
-varStringDecoder;
+
+// Lazy loaded to improve the startup performance.
+letStringDecoder;
 
 util.inherits(Readable,Stream);
 

lib/internal/child_process.js

@@ -14,7 +14,6 @@ const {
 ERR_MISSING_ARGS
 }
 }=require('internal/errors');
-const{ StringDecoder }=require('string_decoder');
 constEventEmitter=require('events');
 constnet=require('net');
 constdgram=require('dgram');
@@ -47,6 +46,9 @@ const {
 
 const{ SocketListSend, SocketListReceive }=SocketList;
 
+// Lazy loaded for startup performance.
+letStringDecoder;
+
 constMAX_HANDLE_RETRANSMISSIONS=3;
 
 // this object contain function to convert TCP objects to native handle objects
@@ -476,6 +478,8 @@ function setupChannel(target, channel) {
 
 constcontrol=newControl(channel);
 
+if(StringDecoder===undefined)
+StringDecoder=require('string_decoder').StringDecoder;
 vardecoder=newStringDecoder('utf8');
 varjsonBuffer='';
 varpendingHandle=null;

lib/internal/crypto/cipher.js

@@ -28,11 +28,13 @@ const {
 
 constassert=require('assert');
 constLazyTransform=require('internal/streams/lazy_transform');
-const{ StringDecoder }=require('string_decoder');
 
 const{ inherits }=require('util');
 const{ deprecate, normalizeEncoding }=require('internal/util');
 
+// Lazy loaded for startup performance.
+letStringDecoder;
+
 functionrsaFunctionFor(method,defaultPadding){
 returnfunction(options,buffer){
 constkey=options.key||options;
@@ -49,6 +51,8 @@ const privateDecrypt = rsaFunctionFor(_privateDecrypt, RSA_PKCS1_OAEP_PADDING);
 
 functiongetDecoder(decoder,encoding){
 encoding=normalizeEncoding(encoding);
+if(StringDecoder===undefined)
+StringDecoder=require('string_decoder').StringDecoder;
 decoder=decoder||newStringDecoder(encoding);
 assert(decoder.encoding===encoding,'Cannot change encoding');
 returndecoder;

lib/readline.js

@@ -35,7 +35,6 @@ const {
 const{ debug, inherits }=require('util');
 const{ Buffer }=require('buffer');
 constEventEmitter=require('events');
-const{ StringDecoder }=require('string_decoder');
 const{
 CSI,
  emitKeys,
@@ -52,6 +51,9 @@ const {
  kClearScreenDown
 }=CSI;
 
+// Lazy load StringDecoder for startup performance.
+letStringDecoder;
+
 constkHistorySize=30;
 constkMincrlfDelay=100;
 // \r\n, \n, or \r followed by something other than \n
@@ -73,6 +75,9 @@ function Interface(input, output, completer, terminal) {
 returnnewInterface(input,output,completer,terminal);
 }
 
+if(StringDecoder===undefined)
+StringDecoder=require('string_decoder').StringDecoder;
+
 this._sawReturnAt=0;
 this.isCompletionEnabled=true;
 this._sawKeyPress=false;
@@ -987,6 +992,9 @@ Interface.prototype._ttyWrite = function(s, key) {
 
 functionemitKeypressEvents(stream,iface){
 if(stream[KEYPRESS_DECODER])return;
+
+if(StringDecoder===undefined)
+StringDecoder=require('string_decoder').StringDecoder;
 stream[KEYPRESS_DECODER]=newStringDecoder('utf8');
 
 stream[ESCAPE_DECODER]=emitKeys(stream);