alternative implementation

Co-authored-by: Nikita Skovoroda <[email protected]>

Author: gurgunday

lib/buffer.js

@@ -252,7 +252,11 @@ function _copyActual(source, target, targetStart, sourceStart, sourceEnd) {
   if (nb <= 0)
     return 0;
 
-  _copy(source, target, targetStart, sourceStart, nb);
+  if (sourceStart === 0 && nb === sourceLen) {
+    TypedArrayPrototypeSet(target, source, targetStart);
+  } else {
+    _copy(source, target, targetStart, sourceStart, nb);
+  }
 
   return nb;
 }
@@ -582,9 +586,8 @@ Buffer.concat = function concat(list, length) {
   if (length === undefined) {
     length = 0;
     for (let i = 0; i < list.length; i++) {
-      const bufLength = list[i].length;
-      if (bufLength) {
-        length += bufLength;
+      if (list[i].length) {
+        length += list[i].length;
       }
     }
   } else {
@@ -601,27 +604,7 @@ Buffer.concat = function concat(list, length) {
       throw new ERR_INVALID_ARG_TYPE(
         `list[${i}]`, ['Buffer', 'Uint8Array'], list[i]);
     }
-
-    const bufLength = buf.length;
-    if (bufLength === 0 || pos >= length) {
-      // Empty buf, or destination is full and subsequent copies are no-ops.
-      // We don't break to preserve compatibility and throw if isUint8Array fails.
-      continue;
-    }
-
-    const available = length - pos;
-    const toCopy = bufLength > available ? available : bufLength;
-    if (toCopy === bufLength) {
-      TypedArrayPrototypeSet(buffer, buf, pos);
-    } else {
-      const src = new Uint8Array(
-        TypedArrayPrototypeGetBuffer(buf),
-        TypedArrayPrototypeGetByteOffset(buf),
-        toCopy,
-      );
-      TypedArrayPrototypeSet(buffer, src, pos);
-    }
-    pos += toCopy;
+    pos += _copyActual(buf, buffer, pos, 0, buf.length);
   }
 
   // Note: `length` is always equal to `buffer.length` at this point