buffer: combine checking range of sourceStart in buf.copy

Merging 2 checking range of sourceStart into 1. Plus,
add test case to increase coverage if sourceStart is greater
than length of source.
PR-URL: #47758
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: deokjinkim

lib/buffer.js

@@ -231,8 +231,8 @@ function _copy(source, target, targetStart, sourceStart, sourceEnd) {
 sourceStart=0;
 }else{
 sourceStart=toInteger(sourceStart,0);
-if(sourceStart<0)
-thrownewERR_OUT_OF_RANGE('sourceStart','>= 0',sourceStart);
+if(sourceStart<0||sourceStart>source.length)
+thrownewERR_OUT_OF_RANGE('sourceStart',`>= 0 && <= ${source.length}`,sourceStart);
 }
 
 if(sourceEnd===undefined){
@@ -246,12 +246,6 @@ function _copy(source, target, targetStart, sourceStart, sourceEnd) {
 if(targetStart>=target.length||sourceStart>=sourceEnd)
 return0;
 
-if(sourceStart>source.length){
-thrownewERR_OUT_OF_RANGE('sourceStart',
-`<= ${source.length}`,
-sourceStart);
-}
-
 return_copyActual(source,target,targetStart,sourceStart,sourceEnd);
 }
 

test/parallel/test-buffer-alloc.js

@@ -124,7 +124,7 @@ b.copy(Buffer.alloc(0), 1, 1, 1);
 b.copy(Buffer.alloc(1),1,1,1);
 
 // Try to copy 0 bytes from past the end of the source buffer
-b.copy(Buffer.alloc(1),0,2048,2048);
+b.copy(Buffer.alloc(1),0,1024,1024);
 
 // Testing for smart defaults and ability to pass string values as offset
 {

test/parallel/test-buffer-copy.js

@@ -155,8 +155,15 @@ assert.throws(
 {
 code: 'ERR_OUT_OF_RANGE',
 name: 'RangeError',
-message: 'The value of "sourceStart" is out of range. '+
-'It must be >= 0. Received -1'
+}
+);
+
+// Copy throws if sourceStart is greater than length of source
+assert.throws(
+()=>Buffer.allocUnsafe(5).copy(Buffer.allocUnsafe(5),0,100),
+{
+code: 'ERR_OUT_OF_RANGE',
+name: 'RangeError',
 }
 );