Replace usage of StringBuilder by AppendableCharSequence for performance reasons

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

@@ -22,6 +22,7 @@ import io.netty.channel.ChannelPipeline;
 import io.netty.handler.codec.DecoderResult;
 import io.netty.handler.codec.ReplayingDecoder;
 import io.netty.handler.codec.TooLongFrameException;
+import io.netty.util.internal.AppendableCharSequence;
 
 import java.util.List;
 
@@ -111,7 +112,7 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
     private long chunkSize;
     private int headerSize;
     private int contentRead;
-    private final StringBuilder sb = new StringBuilder(128);
+    private final AppendableCharSequence sb = new AppendableCharSequence(128);
 
     /**
      * The internal state of {@link HttpObjectDecoder}.
@@ -330,7 +331,7 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
          * read chunk, read and ignore the CRLF and repeat until 0
          */
         case READ_CHUNK_SIZE: try {
-            StringBuilder line = readLine(buffer, maxInitialLineLength);
+            AppendableCharSequence line = readLine(buffer, maxInitialLineLength);
             int chunkSize = getChunkSize(line.toString());
             this.chunkSize = chunkSize;
             if (chunkSize == 0) {
@@ -580,7 +581,7 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
         final HttpMessage message = this.message;
         final HttpHeaders headers = message.headers();
 
-        StringBuilder line = readHeader(buffer);
+        AppendableCharSequence line = readHeader(buffer);
         String name = null;
         String value = null;
         if (line.length() > 0) {
@@ -624,7 +625,7 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
 
     private LastHttpContent readTrailingHeaders(ByteBuf buffer) {
         headerSize = 0;
-        StringBuilder line = readHeader(buffer);
+        AppendableCharSequence line = readHeader(buffer);
         String lastHeader = null;
         if (line.length() > 0) {
             LastHttpContent trailer = new DefaultLastHttpContent(Unpooled.EMPTY_BUFFER, validateHeaders);
@@ -659,9 +660,9 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
         return LastHttpContent.EMPTY_LAST_CONTENT;
     }
 
-    private StringBuilder readHeader(ByteBuf buffer) {
+    private AppendableCharSequence readHeader(ByteBuf buffer) {
-        StringBuilder sb = this.sb;
+        AppendableCharSequence sb = this.sb;
-        sb.setLength(0);
+        sb.reset();
         int headerSize = this.headerSize;
 
         loop:
@@ -716,9 +717,9 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
         return Integer.parseInt(hex, 16);
     }
 
-    private StringBuilder readLine(ByteBuf buffer, int maxLineLength) {
+    private AppendableCharSequence readLine(ByteBuf buffer, int maxLineLength) {
-        StringBuilder sb = this.sb;
+        AppendableCharSequence sb = this.sb;
-        sb.setLength(0);
+        sb.reset();
         int lineLength = 0;
         while (true) {
             byte nextByte = buffer.readByte();
@@ -745,7 +746,7 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
         }
     }
 
-    private static String[] splitInitialLine(StringBuilder sb) {
+    private static String[] splitInitialLine(AppendableCharSequence sb) {
         int aStart;
         int aEnd;
         int bStart;
@@ -768,7 +769,7 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
                 cStart < cEnd? sb.substring(cStart, cEnd) : "" };
     }
 
-    private static String[] splitHeader(StringBuilder sb) {
+    private static String[] splitHeader(AppendableCharSequence sb) {
         final int length = sb.length();
         int nameStart;
         int nameEnd;

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

@@ -0,0 +1,137 @@
+/*
+ * Copyright 2013 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.util.internal;
+
+
+import java.util.Arrays;
+
+public final class AppendableCharSequence implements CharSequence, Appendable {
+    private char[] chars;
+    private int pos;
+
+    public AppendableCharSequence(int length) {
+        chars = new char[length];
+    }
+
+    private AppendableCharSequence(char[] chars) {
+        this.chars = chars;
+    }
+
+    @Override
+    public int length() {
+        return pos;
+    }
+
+    @Override
+    public char charAt(int index) {
+        if (index > pos) {
+            throw new IndexOutOfBoundsException();
+        }
+        return chars[index];
+    }
+
+    @Override
+    public AppendableCharSequence subSequence(int start, int end) {
+        return new AppendableCharSequence(Arrays.copyOfRange(chars, start, end));
+    }
+
+    @Override
+    public AppendableCharSequence append(char c) {
+        if (pos == chars.length) {
+            char[] old = chars;
+            // double it
+            int len = old.length << 1;
+            if (len < 0) {
+                throw new IllegalStateException();
+            }
+            chars = new char[len];
+            System.arraycopy(old, 0, chars, 0, old.length);
+        }
+        chars[pos++] = c;
+        return this;
+    }
+
+    @Override
+    public AppendableCharSequence append(CharSequence csq) {
+        return append(csq, 0, csq.length());
+    }
+
+    @Override
+    public AppendableCharSequence append(CharSequence csq, int start, int end) {
+        if (csq.length() < end) {
+            throw new IndexOutOfBoundsException();
+        }
+        int length = end - start;
+        if (length > chars.length - pos) {
+            chars = expand(chars, pos + length, pos);
+        }
+        if (csq instanceof AppendableCharSequence) {
+            // Optimize append operations via array copy
+            AppendableCharSequence seq = (AppendableCharSequence) csq;
+            char[] src = seq.chars;
+            System.arraycopy(src, start, chars, pos, length);
+            pos += length;
+            return this;
+        }
+        for (int i = start; i < end; i++) {
+            chars[pos++] = csq.charAt(i);
+        }
+
+        return this;
+    }
+
+    /**
+     * Reset the {@link AppendableCharSequence}. Be aware this will only reset the current internal position and not
+     * shrink the internal char array.
+     */
+    public void reset() {
+        pos = 0;
+    }
+
+    @Override
+    public String toString() {
+        return new String(chars, 0, pos);
+    }
+
+    /**
+     * Create a new {@link String} from the given start to end.
+     */
+    public String substring(int start, int end) {
+        int length = end - start;
+        if (start > pos || length > pos) {
+            throw new IndexOutOfBoundsException();
+        }
+        return new String(chars, start, length);
+    }
+
+    private static char[] expand(char[] array, int neededSpace, int size) {
+        int newCapacity = array.length;
+        do {
+            // double capacity until it is big enough
+            newCapacity <<= 1;
+
+            if (newCapacity < 0) {
+                throw new IllegalStateException();
+            }
+
+        } while (neededSpace > newCapacity);
+
+        char[] newArray = new char[newCapacity];
+        System.arraycopy(array, 0, newArray, 0, size);
+
+        return newArray;
+    }
+}

common/src/test/java/io/netty/util/internal/AppendableCharSequenceTest.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2013 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.util.internal;
+
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class AppendableCharSequenceTest {
+
+    @Test
+    public void testSimpleAppend() {
+        testSimpleAppend0(new AppendableCharSequence(128));
+    }
+
+    @Test
+    public void testAppendString() {
+        testAppendString0(new AppendableCharSequence(128));
+    }
+
+    @Test
+    public void testAppendAppendableCharSequence() {
+        AppendableCharSequence seq = new AppendableCharSequence(128);
+
+        String text = "testdata";
+        AppendableCharSequence seq2 = new AppendableCharSequence(128);
+        seq2.append(text);
+        seq.append(seq2);
+
+        assertEquals(text, seq.toString());
+        assertEquals(text.substring(1, text.length() - 2), seq.substring(1, text.length() - 2));
+
+        assertEqualsChars(text, seq);
+    }
+
+    @Test
+    public void testSimpleAppendWithExpand() {
+        testSimpleAppend0(new AppendableCharSequence(2));
+    }
+
+    @Test
+    public void testAppendStringWithExpand() {
+        testAppendString0(new AppendableCharSequence(2));
+    }
+
+    private static void testSimpleAppend0(AppendableCharSequence seq) {
+        String text = "testdata";
+        for (int i = 0; i < text.length(); i++) {
+            seq.append(text.charAt(i));
+        }
+
+        assertEquals(text, seq.toString());
+        assertEquals(text.substring(1, text.length() - 2), seq.substring(1, text.length() - 2));
+
+        assertEqualsChars(text, seq);
+
+        seq.reset();
+        assertEquals(0, seq.length());
+    }
+
+    private static void testAppendString0(AppendableCharSequence seq) {
+        String text = "testdata";
+        seq.append(text);
+
+        assertEquals(text, seq.toString());
+        assertEquals(text.substring(1, text.length() - 2), seq.substring(1, text.length() - 2));
+
+        assertEqualsChars(text, seq);
+
+        seq.reset();
+        assertEquals(0, seq.length());
+    }
+
+    private static  void assertEqualsChars(CharSequence seq1, CharSequence seq2) {
+        assertEquals(seq1.length(), seq2.length());
+        for (int i = 0; i < seq1.length(); i++) {
+            assertEquals(seq1.charAt(i), seq2.charAt(i));
+        }
+    }
+}