buffer: optimize write()

PR-URL: #12361
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: mscdex

benchmark/buffers/buffer-write-string.js

@@ -0,0 +1,70 @@
+'use strict';
+
+const common = require('../common.js');
+const bench = common.createBenchmark(main, {
+  encoding: [
+    '', 'utf8', 'ascii', 'hex', 'UCS-2', 'utf16le', 'latin1', 'binary'
+  ],
+  args: [ '', 'offset', 'offset+length' ],
+  len: [10, 2048],
+  n: [1e7]
+});
+
+function main(conf) {
+  const len = +conf.len;
+  const n = +conf.n;
+  const encoding = conf.encoding;
+  const args = conf.args;
+
+  const string = 'a'.repeat(len);
+  const buf = Buffer.allocUnsafe(len);
+
+  var i;
+
+  switch (args) {
+    case 'offset':
+      if (encoding) {
+        bench.start();
+        for (i = 0; i < n; ++i) {
+          buf.write(string, 0, encoding);
+        }
+        bench.end(n);
+      } else {
+        bench.start();
+        for (i = 0; i < n; ++i) {
+          buf.write(string, 0);
+        }
+        bench.end(n);
+      }
+      break;
+    case 'offset+length':
+      if (encoding) {
+        bench.start();
+        for (i = 0; i < n; ++i) {
+          buf.write(string, 0, buf.length, encoding);
+        }
+        bench.end(n);
+      } else {
+        bench.start();
+        for (i = 0; i < n; ++i) {
+          buf.write(string, 0, buf.length);
+        }
+        bench.end(n);
+      }
+      break;
+    default:
+      if (encoding) {
+        bench.start();
+        for (i = 0; i < n; ++i) {
+          buf.write(string, encoding);
+        }
+        bench.end(n);
+      } else {
+        bench.start();
+        for (i = 0; i < n; ++i) {
+          buf.write(string);
+        }
+        bench.end(n);
+      }
+  }
+}

lib/buffer.js

@@ -728,9 +728,7 @@ Buffer.prototype.fill = function fill(val, start, end, encoding) {
 Buffer.prototype.write = function(string, offset, length, encoding) {
   // Buffer#write(string);
   if (offset === undefined) {
-    encoding = 'utf8';
-    length = this.length;
-    offset = 0;
+    return this.utf8Write(string, 0, this.length);
 
   // Buffer#write(string, encoding)
   } else if (length === undefined && typeof offset === 'string') {
@@ -743,12 +741,17 @@ Buffer.prototype.write = function(string, offset, length, encoding) {
     offset = offset >>> 0;
     if (isFinite(length)) {
       length = length >>> 0;
-      if (encoding === undefined)
-        encoding = 'utf8';
     } else {
       encoding = length;
       length = undefined;
     }
+
+    var remaining = this.length - offset;
+    if (length === undefined || length > remaining)
+      length = remaining;
+
+    if (string.length > 0 && (length < 0 || offset < 0))
+      throw new RangeError('Attempt to write outside buffer bounds');
   } else {
     // if someone is still calling the obsolete form of write(), tell them.
     // we don't want eg buf.write("foo", "utf8", 10) to silently turn into
@@ -757,50 +760,51 @@ Buffer.prototype.write = function(string, offset, length, encoding) {
                     'is no longer supported');
   }
 
-  var remaining = this.length - offset;
-  if (length === undefined || length > remaining)
-    length = remaining;
-
-  if (string.length > 0 && (length < 0 || offset < 0))
-    throw new RangeError('Attempt to write outside buffer bounds');
-
-  if (!encoding)
-    encoding = 'utf8';
-
-  var loweredCase = false;
-  for (;;) {
-    switch (encoding) {
-      case 'hex':
-        return this.hexWrite(string, offset, length);
-
-      case 'utf8':
-      case 'utf-8':
-        return this.utf8Write(string, offset, length);
-
-      case 'ascii':
-        return this.asciiWrite(string, offset, length);
-
-      case 'latin1':
-      case 'binary':
+  if (!encoding) return this.utf8Write(string, offset, length);
+
+  encoding += '';
+  switch (encoding.length) {
+    case 4:
+      if (encoding === 'utf8') return this.utf8Write(string, offset, length);
+      if (encoding === 'ucs2') return this.ucs2Write(string, offset, length);
+      encoding = encoding.toLowerCase();
+      if (encoding === 'utf8') return this.utf8Write(string, offset, length);
+      if (encoding === 'ucs2') return this.ucs2Write(string, offset, length);
+      break;
+    case 5:
+      if (encoding === 'utf-8') return this.utf8Write(string, offset, length);
+      if (encoding === 'ascii') return this.asciiWrite(string, offset, length);
+      if (encoding === 'ucs-2') return this.ucs2Write(string, offset, length);
+      encoding = encoding.toLowerCase();
+      if (encoding === 'utf-8') return this.utf8Write(string, offset, length);
+      if (encoding === 'ascii') return this.asciiWrite(string, offset, length);
+      if (encoding === 'ucs-2') return this.ucs2Write(string, offset, length);
+      break;
+    case 7:
+      if (encoding === 'utf16le' || encoding.toLowerCase() === 'utf16le')
+        return this.ucs2Write(string, offset, length);
+      break;
+    case 8:
+      if (encoding === 'utf-16le' || encoding.toLowerCase() === 'utf-16le')
+        return this.ucs2Write(string, offset, length);
+      break;
+    case 6:
+      if (encoding === 'latin1' || encoding === 'binary')
         return this.latin1Write(string, offset, length);
-
-      case 'base64':
-        // Warning: maxLength not taken into account in base64Write
+      if (encoding === 'base64')
         return this.base64Write(string, offset, length);
-
-      case 'ucs2':
-      case 'ucs-2':
-      case 'utf16le':
-      case 'utf-16le':
-        return this.ucs2Write(string, offset, length);
-
-      default:
-        if (loweredCase)
-          throw new TypeError('Unknown encoding: ' + encoding);
-        encoding = ('' + encoding).toLowerCase();
-        loweredCase = true;
-    }
+      encoding = encoding.toLowerCase();
+      if (encoding === 'latin1' || encoding === 'binary')
+        return this.latin1Write(string, offset, length);
+      if (encoding === 'base64')
+        return this.base64Write(string, offset, length);
+      break;
+    case 3:
+      if (encoding === 'hex' || encoding.toLowerCase() === 'hex')
+        return this.hexWrite(string, offset, length);
+      break;
   }
+  throw new TypeError('Unknown encoding: ' + encoding);
 };