Small performance improvements

Modifications:

- Added a static modifier for CompositeByteBuf.Component.
This class is an inner class, but does not use its embedded reference to the object which created it. This reference makes the instances of the class larger, and may keep the reference to the creator object alive longer than necessary.
- Removed unnecessary boxing/unboxing operations in HttpResponseDecoder, RtspResponseDecoder, PerMessageDeflateClientExtensionHandshaker and PerMessageDeflateServerExtensionHandshaker
A boxed primitive is created from a String, just to extract the unboxed primitive value.
- Removed unnecessary 3 times calculations in DiskAttribute.addContent(...).
- Removed unnecessary checks if file exists before call mkdirs() in NativeLibraryLoader and PlatformDependent.
Because the method mkdirs() has this check inside.
- Removed unnecessary `instanceof AsciiString` check in StompSubframeAggregator.contentLength(StompHeadersSubframe) and StompSubframeDecoder.getContentLength(StompHeaders, long).
Because StompHeaders.get(CharSequence) always returns java.lang.String.

buffer/src/main/java/io/netty/buffer/CompositeByteBuf.java

@@ -1319,7 +1319,7 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf {
         return result + ", components=" + components.size() + ')';
     }
 
-    private final class Component {
+    private static final class Component {
         final ByteBuf buf;
         final int length;
         int offset;

codec-http/src/main/java/io/netty/handler/codec/http/HttpResponseDecoder.java

@@ -110,7 +110,7 @@ public class HttpResponseDecoder extends HttpObjectDecoder {
     protected HttpMessage createMessage(String[] initialLine) {
         return new DefaultHttpResponse(
                 HttpVersion.valueOf(initialLine[0]),
-                new HttpResponseStatus(Integer.valueOf(initialLine[1]), initialLine[2]), validateHeaders);
+                new HttpResponseStatus(Integer.parseInt(initialLine[1]), initialLine[2]), validateHeaders);
     }
 
     @Override

codec-http/src/main/java/io/netty/handler/codec/http/multipart/DiskAttribute.java

@@ -83,13 +83,14 @@ public class DiskAttribute extends AbstractDiskHttpData implements Attribute {
 
     @Override
     public void addContent(ByteBuf buffer, boolean last) throws IOException {
-        int localsize = buffer.readableBytes();
-        checkSize(size + localsize);
-        if (definedSize > 0 && definedSize < size + localsize) {
-            definedSize = size + localsize;
+        final long newDefinedSize = size + buffer.readableBytes();
+        checkSize(newDefinedSize);
+        if (definedSize > 0 && definedSize < newDefinedSize) {
+            definedSize = newDefinedSize;
         }
         super.addContent(buffer, last);
     }
+
     @Override
     public int hashCode() {
         return getName().hashCode();

codec-http/src/main/java/io/netty/handler/codec/rtsp/RtspResponseDecoder.java

@@ -78,7 +78,7 @@ public class RtspResponseDecoder extends RtspObjectDecoder {
     protected HttpMessage createMessage(String[] initialLine) throws Exception {
         return new DefaultHttpResponse(
                 RtspVersions.valueOf(initialLine[0]),
-                new HttpResponseStatus(Integer.valueOf(initialLine[1]), initialLine[2]), validateHeaders);
+                new HttpResponseStatus(Integer.parseInt(initialLine[1]), initialLine[2]), validateHeaders);
     }
 
     @Override

codec-stomp/src/main/java/io/netty/handler/codec/stomp/StompSubframeAggregator.java

@@ -18,7 +18,6 @@ package io.netty.handler.codec.stomp;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelPipeline;
-import io.netty.handler.codec.AsciiString;
 import io.netty.handler.codec.MessageAggregator;
 import io.netty.handler.codec.TooLongFrameException;
 
@@ -70,12 +69,8 @@ public class StompSubframeAggregator
 
     @Override
     protected long contentLength(StompHeadersSubframe start) throws Exception {
-        CharSequence value = start.headers().get(StompHeaders.CONTENT_LENGTH);
-        if (value instanceof AsciiString) {
-            return ((AsciiString) value).parseLong();
-        }
-
-        return Long.parseLong(value.toString());
+        String value = start.headers().get(StompHeaders.CONTENT_LENGTH);
+        return Long.parseLong(value);
     }
 
     @Override

codec-stomp/src/main/java/io/netty/handler/codec/stomp/StompSubframeDecoder.java

@@ -18,7 +18,6 @@ package io.netty.handler.codec.stomp;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelHandlerContext;
-import io.netty.handler.codec.AsciiString;
 import io.netty.handler.codec.DecoderException;
 import io.netty.handler.codec.DecoderResult;
 import io.netty.handler.codec.ReplayingDecoder;
@@ -220,14 +219,10 @@ public class StompSubframeDecoder extends ReplayingDecoder<State> {
     }
 
     private static long getContentLength(StompHeaders headers, long defaultValue) {
-        CharSequence contentLength = headers.get(StompHeaders.CONTENT_LENGTH);
+        String contentLength = headers.get(StompHeaders.CONTENT_LENGTH);
         if (contentLength != null) {
             try {
-                if (contentLength instanceof AsciiString) {
-                    return ((AsciiString) contentLength).parseLong();
-                } else {
-                    return Long.parseLong(contentLength.toString());
-                }
+                return Long.parseLong(contentLength);
             } catch (NumberFormatException ignored) {
                 return defaultValue;
             }

common/src/main/java/io/netty/util/internal/NativeLibraryLoader.java

@@ -44,11 +44,7 @@ public final class NativeLibraryLoader {
         String workdir = SystemPropertyUtil.get("io.netty.native.workdir");
         if (workdir != null) {
             File f = new File(workdir);
-            if (!f.exists()) {
-                // ok to ignore as createTempFile will take care
-                //noinspection ResultOfMethodCallIgnored
-                f.mkdirs();
-            }
+            f.mkdirs();
 
             try {
                 f = f.getAbsoluteFile();
@@ -130,9 +126,7 @@ public final class NativeLibraryLoader {
         }
 
         File f = new File(path);
-        if (!f.exists()) {
-            f.mkdirs();
-        }
+        f.mkdirs();
 
         if (!f.isDirectory()) {
             return null;

common/src/main/java/io/netty/util/internal/PlatformDependent.java

@@ -759,9 +759,7 @@ public final class PlatformDependent {
         }
 
         File f = new File(path);
-        if (!f.exists()) {
-            f.mkdirs();
-        }
+        f.mkdirs();
 
         if (!f.isDirectory()) {
             return null;