buffer: improve from() performance

PR-URL: #31615
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: mscdex

benchmark/buffers/buffer-from.js

@@ -12,37 +12,37 @@ const bench = common.createBenchmark(main, {
 'string-utf8',
 'string-base64',
 'object',
+'uint8array',
+'uint16array',
 ],
 len: [100,2048],
 n: [8e5]
 });
 
 functionmain({ len, n, source }){
-constarray=newArray(len).fill(42);
-constarrayBuf=newArrayBuffer(len);
-conststr='a'.repeat(len);
-constbuffer=Buffer.allocUnsafe(len);
-constuint8array=newUint8Array(len);
-constobj={length: null};// Results in a new, empty Buffer
-
 leti=0;
 
 switch(source){
-case'array':
+case'array': {
+constarray=newArray(len).fill(42);
 bench.start();
 for(i=0;i<n;i++){
 Buffer.from(array);
 }
 bench.end(n);
 break;
-case'arraybuffer':
+}
+case'arraybuffer': {
+constarrayBuf=newArrayBuffer(len);
 bench.start();
 for(i=0;i<n;i++){
 Buffer.from(arrayBuf);
 }
 bench.end(n);
 break;
-case'arraybuffer-middle':
+}
+case'arraybuffer-middle': {
+constarrayBuf=newArrayBuffer(len);
 constoffset=~~(len/4);
 constlength=~~(len/2);
 bench.start();
@@ -51,48 +51,70 @@ function main({ len, n, source }) {
 }
 bench.end(n);
 break;
-case'buffer':
+}
+case'buffer': {
+constbuffer=Buffer.allocUnsafe(len);
 bench.start();
 for(i=0;i<n;i++){
 Buffer.from(buffer);
 }
 bench.end(n);
 break;
-case'uint8array':
+}
+case'uint8array': {
+constuint8array=newUint8Array(len);
 bench.start();
 for(i=0;i<n;i++){
 Buffer.from(uint8array);
 }
 bench.end(n);
 break;
-case'string':
+}
+case'uint16array': {
+constuint16array=newUint16Array(len);
+bench.start();
+for(i=0;i<n;i++){
+Buffer.from(uint16array);
+}
+bench.end(n);
+break;
+}
+case'string': {
+conststr='a'.repeat(len);
 bench.start();
 for(i=0;i<n;i++){
 Buffer.from(str);
 }
 bench.end(n);
 break;
-case'string-utf8':
+}
+case'string-utf8': {
+conststr='a'.repeat(len);
 bench.start();
 for(i=0;i<n;i++){
 Buffer.from(str,'utf8');
 }
 bench.end(n);
 break;
-case'string-base64':
+}
+case'string-base64': {
+conststr='a'.repeat(len);
 bench.start();
 for(i=0;i<n;i++){
 Buffer.from(str,'base64');
 }
 bench.end(n);
 break;
-case'object':
+}
+case'object': {
+constobj={length: null};// Results in a new, empty Buffer
 bench.start();
 for(i=0;i<n;i++){
 Buffer.from(obj);
 }
 bench.end(n);
 break;
+}
 default:
 assert.fail('Should not get here');
 }

lib/buffer.js

@@ -452,14 +452,6 @@ function fromString(string, encoding) {
 returnfromStringFast(string,ops);
 }
 
-functionfromArrayLike(obj){
-constlength=obj.length;
-constb=allocate(length);
-for(leti=0;i<length;i++)
-b[i]=obj[i];
-returnb;
-}
-
 functionfromArrayBuffer(obj,byteOffset,length){
 // Convert byteOffset to integer
 if(byteOffset===undefined){
@@ -491,17 +483,22 @@ function fromArrayBuffer(obj, byteOffset, length) {
 returnnewFastBuffer(obj,byteOffset,length);
 }
 
-functionfromObject(obj){
-if(isUint8Array(obj)){
-constb=allocate(obj.length);
-
-if(b.length===0)
-returnb;
-
-_copy(obj,b,0,0,obj.length);
+functionfromArrayLike(obj){
+if(obj.length<=0)
+returnnewFastBuffer();
+if(obj.length<(Buffer.poolSize>>>1)){
+if(obj.length>(poolSize-poolOffset))
+createPool();
+constb=newFastBuffer(allocPool,poolOffset,obj.length);
+b.set(obj,0);
+poolOffset+=obj.length;
+alignPool();
 returnb;
 }
+returnnewFastBuffer(obj);
+}
 
+functionfromObject(obj){
 if(obj.length!==undefined||isAnyArrayBuffer(obj.buffer)){
 if(typeofobj.length!=='number'){
 returnnewFastBuffer();