buffer: simplify code

This refactors some code for simplicity. It also removes a call
indirection used in the buffers custom inspect function.

PR-URL: #25151
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Masashi Hirano <shisama07@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

lib/buffer.js

@@ -298,11 +298,13 @@ Buffer.allocUnsafeSlow = function allocUnsafeSlow(size) {
 // If --zero-fill-buffers command line argument is set, a zero-filled
 // buffer is returned.
 function SlowBuffer(length) {
+  const len = +length;
   // eslint-disable-next-line eqeqeq
-  if (+length != length)
+  if (len != length)
     length = 0;
-  assertSize(+length);
-  return createUnsafeBuffer(+length);
+  else
+    assertSize(len);
+  return createUnsafeBuffer(len);
 }
 
 Object.setPrototypeOf(SlowBuffer.prototype, Uint8Array.prototype);
@@ -319,9 +321,8 @@ function allocate(size) {
     poolOffset += size;
     alignPool();
     return b;
-  } else {
-    return createUnsafeBuffer(size);
   }
+  return createUnsafeBuffer(size);
 }
 
 function fromString(string, encoding) {
@@ -639,21 +640,18 @@ Buffer.prototype.toString = function toString(encoding, start, end) {
   }
 
   const len = this.length;
-  if (len === 0)
-    return '';
 
-  if (!start || start < 0)
+  if (start <= 0)
     start = 0;
   else if (start >= len)
     return '';
+  else
+    start |= 0;
 
   if (end === undefined || end > len)
     end = len;
-  else if (end <= 0)
-    return '';
-
-  start |= 0;
-  end |= 0;
+  else
+    end |= 0;
 
   if (end <= start)
     return '';
@@ -672,10 +670,10 @@ Buffer.prototype.equals = function equals(otherBuffer) {
 };
 
 // Override how buffers are presented by util.inspect().
-Buffer.prototype[customInspectSymbol] = function inspect() {
-  var str = '';
-  var max = exports.INSPECT_MAX_BYTES;
-  str = this.toString('hex', 0, max).replace(/(.{2})/g, '$1 ').trim();
+Buffer.prototype[customInspectSymbol] = function inspect(recurseTimes, ctx) {
+  const max = exports.INSPECT_MAX_BYTES;
+  const actualMax = Math.min(max, this.length);
+  let str = this.hexSlice(0, actualMax).replace(/(.{2})/g, '$1 ').trim();
   const remaining = this.length - max;
   if (remaining > 0)
     str += ` ... ${remaining} more byte${remaining > 1 ? 's' : ''}`;
@@ -977,9 +975,8 @@ Buffer.prototype.toJSON = function toJSON() {
     for (var i = 0; i < this.length; ++i)
       data[i] = this[i];
     return { type: 'Buffer', data };
-  } else {
-    return { type: 'Buffer', data: [] };
   }
+  return { type: 'Buffer', data: [] };
 };
 
 function adjustOffset(offset, length) {