avoid .toLowerCase() call in Buffer#write()

Avoid a costly String#toLowerCase() call in Buffer#write() in the
common case, i.e., that the string is already lowercase.  Reduces
the running time of the following benchmark by about 40%:

for (var b = Buffer(1), i = 0; i < 25e6; ++i) b.write('x', 'ucs2');

From
https://github.com/iojs/io.js/commit/4ddd6406ce1c474e1a54a5aa9b56f755490
2fd10

diff --git a/index.js b/index.js
index ba03fc280d083d17e412d4c48d1973b999d752fb..ed987adf17749e7a9a3455f72e1b8ac5293f358d 100644 (file)
--- a/index.js
+++ b/index.js
@@ -401,71 +401,80 @@ function base64Write (buf, string, offset, length) {
   return charsWritten
 }
 
-function utf16leWrite (buf, string, offset, length) {
-  var charsWritten = blitBuffer(utf16leToBytes(string, buf.length - offset), buf, offset, length)
-  return charsWritten
+function ucs2Write (buf, string, offset, length) {
+  return blitBuffer(utf16leToBytes(string, buf.length - offset), buf, offset, length)
 }
 
 Buffer.prototype.write = function write (string, offset, length, encoding) {
-  // Support both (string, offset, length, encoding)
-  // and the legacy (string, encoding, offset, length)
-  if (isFinite(offset)) {
-    if (!isFinite(length)) {
+  // Buffer#write(string)
+  if (offset === undefined) {
+    encoding = 'utf8'
+    length = this.length
+    offset = 0
+  // Buffer#write(string, encoding)
+  } else if (length === undefined && typeof offset === 'string') {
+    encoding = offset
+    length = this.length
+    offset = 0
+  // Buffer#write(string, offset[, length][, encoding])
+  } else if (isFinite(offset)) {
+    offset = offset >>> 0
+    if (isFinite(length)) {
+      length = length >>> 0
+      if (encoding === undefined) encoding = 'utf8'
+    } else {
       encoding = length
       length = undefined
     }
-  } else {  // legacy
+  // legacy write(string, encoding, offset, length) - remove in v0.13
+  } else {
     var swap = encoding
     encoding = offset
-    offset = length
+    offset = length >>> 0
     length = swap
   }
 
-  offset = Number(offset) || 0
+  var remaining = this.length - offset
+  if (length === undefined || length > remaining) length = remaining
 
-  if (length < 0 || offset < 0 || offset > this.length) {
+  if ((string.length > 0 && (length < 0 || offset < 0)) || offset > this.length) {
     throw new RangeError('attempt to write outside buffer bounds')
   }
 
-  var remaining = this.length - offset
-  if (!length) {
-    length = remaining
-  } else {
-    length = Number(length)
-    if (length > remaining) {
-      length = remaining
-    }
-  }
-  encoding = String(encoding || 'utf8').toLowerCase()
+  if (!encoding) encoding = 'utf8'
 
-  var ret
-  switch (encoding) {
-    case 'hex':
-      ret = hexWrite(this, string, offset, length)
-      break
-    case 'utf8':
-    case 'utf-8':
-      ret = utf8Write(this, string, offset, length)
-      break
-    case 'ascii':
-      ret = asciiWrite(this, string, offset, length)
-      break
-    case 'binary':
-      ret = binaryWrite(this, string, offset, length)
-      break
-    case 'base64':
-      ret = base64Write(this, string, offset, length)
-      break
-    case 'ucs2':
-    case 'ucs-2':
-    case 'utf16le':
-    case 'utf-16le':
-      ret = utf16leWrite(this, string, offset, length)
-      break
-    default:
-      throw new TypeError('Unknown encoding: ' + encoding)
+  var loweredCase = false
+  for (;;) {
+    switch (encoding) {
+      case 'hex':
+        return hexWrite(this, string, offset, length)
+
+      case 'utf8':
+      case 'utf-8':
+        return utf8Write(this, string, offset, length)
+
+      case 'ascii':
+        return asciiWrite(this, string, offset, length)
+
+      case 'binary':
+        return binaryWrite(this, string, offset, length)
+
+      case 'base64':
+        // Warning: maxLength not taken into account in base64Write
+        return base64Write(this, string, offset, length)
+
+      case 'ucs2':
+      case 'ucs-2':
+      case 'utf16le':
+      case 'utf-16le':
+        return ucs2Write(this, string, offset, length)
+
+      default:
+        if (loweredCase) throw new TypeError('Unknown encoding: ' + encoding)
+        encoding = ('' + encoding).toLowerCase()
+        loweredCase = true
+    }
   }
-  return ret
 }
 
 Buffer.prototype.toJSON = function toJSON () {