fs: extract start and end check into checkPosition

PR-URL: nodejs#25264
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

lib/internal/fs/streams.js

@@ -37,6 +37,19 @@ function allocNewPool(poolSize) {
   pool.used = 0;
 }
 
+// Check the `this.start` and `this.end` of stream.
+function checkPosition(pos, name) {
+  if (!Number.isSafeInteger(pos)) {
+    validateNumber(pos, name);
+    if (!Number.isInteger(pos))
+      throw new ERR_OUT_OF_RANGE(name, 'an integer', pos);
+    throw new ERR_OUT_OF_RANGE(name, '>= 0 and <= 2 ** 53 - 1', pos);
+  }
+  if (pos < 0) {
+    throw new ERR_OUT_OF_RANGE(name, '>= 0 and <= 2 ** 53 - 1', pos);
+  }
+}
+
 function ReadStream(path, options) {
   if (!(this instanceof ReadStream))
     return new ReadStream(path, options);
@@ -65,41 +78,15 @@ function ReadStream(path, options) {
   this.closed = false;
 
   if (this.start !== undefined) {
-    if (!Number.isSafeInteger(this.start)) {
-      validateNumber(this.start, 'start');
-      if (!Number.isInteger(this.start))
-        throw new ERR_OUT_OF_RANGE('start', 'an integer', this.start);
-      throw new ERR_OUT_OF_RANGE(
-        'start',
-        '>= 0 and <= 2 ** 53 - 1',
-        this.start
-      );
-    }
-    if (this.start < 0) {
-      throw new ERR_OUT_OF_RANGE(
-        'start',
-        '>= 0 and <= 2 ** 53 - 1',
-        this.start
-      );
-    }
+    checkPosition(this.start, 'start');
 
     this.pos = this.start;
   }
 
   if (this.end === undefined) {
     this.end = Infinity;
   } else if (this.end !== Infinity) {
-    if (!Number.isSafeInteger(this.end)) {
-      if (typeof this.end !== 'number')
-        throw new ERR_INVALID_ARG_TYPE('end', 'number', this.end);
-      if (!Number.isInteger(this.end))
-        throw new ERR_OUT_OF_RANGE('end', 'an integer', this.end);
-      throw new ERR_OUT_OF_RANGE('end', '>= 0 and <= 2 ** 53 - 1', this.end);
-    }
-
-    if (this.end < 0) {
-      throw new ERR_OUT_OF_RANGE('end', '>= 0 and <= 2 ** 53 - 1', this.end);
-    }
+    checkPosition(this.end, 'end');
 
     if (this.start !== undefined && this.start > this.end) {
       throw new ERR_OUT_OF_RANGE(