http://netty.io/netty-all/: Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers and clients. (The Netty Project) 
public final class io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionUtil
  minor version: 0
  major version: 59
  flags: flags: (0x0031) ACC_PUBLIC, ACC_FINAL, ACC_SUPER
  this_class: io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionUtil
  super_class: java.lang.Object
{
  private static final java.lang.String EXTENSION_SEPARATOR;
    descriptor: Ljava/lang/String;
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL
    ConstantValue: ","

  private static final java.lang.String PARAMETER_SEPARATOR;
    descriptor: Ljava/lang/String;
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL
    ConstantValue: ";"

  private static final char PARAMETER_EQUAL;
    descriptor: C
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL
    ConstantValue: 61

  private static final java.util.regex.Pattern PARAMETER;
    descriptor: Ljava/util/regex/Pattern;
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL

  static void <clinit>();
    descriptor: ()V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=1, locals=0, args_size=0
         0: .line 37
            ldc "^([^=]+)(=[\\\"]?([^\\\"]+)[\\\"]?)?$"
            invokestatic java.util.regex.Pattern.compile:(Ljava/lang/String;)Ljava/util/regex/Pattern;
            putstatic io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionUtil.PARAMETER:Ljava/util/regex/Pattern;
            return
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  static boolean isWebsocketUpgrade(io.netty.handler.codec.http.HttpHeaders);
    descriptor: (Lio/netty/handler/codec/http/HttpHeaders;)Z
    flags: (0x0008) ACC_STATIC
    Code:
      stack=4, locals=1, args_size=1
        start local 0 // io.netty.handler.codec.http.HttpHeaders headers
         0: .line 40
            aload 0 /* headers */
            getstatic io.netty.handler.codec.http.HttpHeaderNames.CONNECTION:Lio/netty/util/AsciiString;
            getstatic io.netty.handler.codec.http.HttpHeaderValues.UPGRADE:Lio/netty/util/AsciiString;
            iconst_1
            invokevirtual io.netty.handler.codec.http.HttpHeaders.containsValue:(Ljava/lang/CharSequence;Ljava/lang/CharSequence;Z)Z
            ifeq 3
         1: .line 41
            aload 0 /* headers */
            getstatic io.netty.handler.codec.http.HttpHeaderNames.UPGRADE:Lio/netty/util/AsciiString;
            getstatic io.netty.handler.codec.http.HttpHeaderValues.WEBSOCKET:Lio/netty/util/AsciiString;
            iconst_1
            invokevirtual io.netty.handler.codec.http.HttpHeaders.contains:(Ljava/lang/CharSequence;Ljava/lang/CharSequence;Z)Z
            ifeq 3
         2: .line 40
            iconst_1
            ireturn
      StackMap locals:
      StackMap stack:
         3: iconst_0
            ireturn
        end local 0 // io.netty.handler.codec.http.HttpHeaders headers
      LocalVariableTable:
        Start  End  Slot     Name  Signature
            0    4     0  headers  Lio/netty/handler/codec/http/HttpHeaders;
    MethodParameters:
         Name  Flags
      headers  

  public static java.util.List<io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionData> extractExtensions(java.lang.String);
    descriptor: (Ljava/lang/String;)Ljava/util/List;
    flags: (0x0009) ACC_PUBLIC, ACC_STATIC
    Code:
      stack=5, locals=13, args_size=1
        start local 0 // java.lang.String extensionHeader
         0: .line 45
            aload 0 /* extensionHeader */
            ldc ","
            invokevirtual java.lang.String.split:(Ljava/lang/String;)[Ljava/lang/String;
            astore 1 /* rawExtensions */
        start local 1 // java.lang.String[] rawExtensions
         1: .line 46
            aload 1 /* rawExtensions */
            arraylength
            ifle 23
         2: .line 47
            new java.util.ArrayList
            dup
            aload 1 /* rawExtensions */
            arraylength
            invokespecial java.util.ArrayList.<init>:(I)V
            astore 2 /* extensions */
        start local 2 // java.util.List extensions
         3: .line 48
            aload 1 /* rawExtensions */
            dup
            astore 6
            arraylength
            istore 5
            iconst_0
            istore 4
            goto 21
      StackMap locals: java.lang.String java.lang.String[] java.util.List top int int java.lang.String[]
      StackMap stack:
         4: aload 6
            iload 4
            aaload
            astore 3 /* rawExtension */
        start local 3 // java.lang.String rawExtension
         5: .line 49
            aload 3 /* rawExtension */
            ldc ";"
            invokevirtual java.lang.String.split:(Ljava/lang/String;)[Ljava/lang/String;
            astore 7 /* extensionParameters */
        start local 7 // java.lang.String[] extensionParameters
         6: .line 50
            aload 7 /* extensionParameters */
            iconst_0
            aaload
            invokevirtual java.lang.String.trim:()Ljava/lang/String;
            astore 8 /* name */
        start local 8 // java.lang.String name
         7: .line 52
            aload 7 /* extensionParameters */
            arraylength
            iconst_1
            if_icmple 18
         8: .line 53
            new java.util.HashMap
            dup
            aload 7 /* extensionParameters */
            arraylength
            iconst_1
            isub
            invokespecial java.util.HashMap.<init>:(I)V
            astore 9 /* parameters */
        start local 9 // java.util.Map parameters
         9: .line 54
            iconst_1
            istore 10 /* i */
        start local 10 // int i
        10: goto 16
        11: .line 55
      StackMap locals: java.lang.String java.lang.String[] java.util.List java.lang.String int int java.lang.String[] java.lang.String[] java.lang.String java.util.Map int
      StackMap stack:
            aload 7 /* extensionParameters */
            iload 10 /* i */
            aaload
            invokevirtual java.lang.String.trim:()Ljava/lang/String;
            astore 11 /* parameter */
        start local 11 // java.lang.String parameter
        12: .line 56
            getstatic io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionUtil.PARAMETER:Ljava/util/regex/Pattern;
            aload 11 /* parameter */
            invokevirtual java.util.regex.Pattern.matcher:(Ljava/lang/CharSequence;)Ljava/util/regex/Matcher;
            astore 12 /* parameterMatcher */
        start local 12 // java.util.regex.Matcher parameterMatcher
        13: .line 57
            aload 12 /* parameterMatcher */
            invokevirtual java.util.regex.Matcher.matches:()Z
            ifeq 15
            aload 12 /* parameterMatcher */
            iconst_1
            invokevirtual java.util.regex.Matcher.group:(I)Ljava/lang/String;
            ifnull 15
        14: .line 58
            aload 9 /* parameters */
            aload 12 /* parameterMatcher */
            iconst_1
            invokevirtual java.util.regex.Matcher.group:(I)Ljava/lang/String;
            aload 12 /* parameterMatcher */
            iconst_3
            invokevirtual java.util.regex.Matcher.group:(I)Ljava/lang/String;
            invokeinterface java.util.Map.put:(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
            pop
        end local 12 // java.util.regex.Matcher parameterMatcher
        end local 11 // java.lang.String parameter
        15: .line 54
      StackMap locals:
      StackMap stack:
            iinc 10 /* i */ 1
      StackMap locals:
      StackMap stack:
        16: iload 10 /* i */
            aload 7 /* extensionParameters */
            arraylength
            if_icmplt 11
        end local 10 // int i
        17: .line 61
            goto 19
        end local 9 // java.util.Map parameters
        18: .line 62
      StackMap locals:
      StackMap stack:
            invokestatic java.util.Collections.emptyMap:()Ljava/util/Map;
            astore 9 /* parameters */
        start local 9 // java.util.Map parameters
        19: .line 64
      StackMap locals: java.util.Map
      StackMap stack:
            aload 2 /* extensions */
            new io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionData
            dup
            aload 8 /* name */
            aload 9 /* parameters */
            invokespecial io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionData.<init>:(Ljava/lang/String;Ljava/util/Map;)V
            invokeinterface java.util.List.add:(Ljava/lang/Object;)Z
            pop
        end local 9 // java.util.Map parameters
        end local 8 // java.lang.String name
        end local 7 // java.lang.String[] extensionParameters
        end local 3 // java.lang.String rawExtension
        20: .line 48
            iinc 4 1
      StackMap locals: java.lang.String java.lang.String[] java.util.List top int int java.lang.String[]
      StackMap stack:
        21: iload 4
            iload 5
            if_icmplt 4
        22: .line 66
            aload 2 /* extensions */
            areturn
        end local 2 // java.util.List extensions
        23: .line 68
      StackMap locals: java.lang.String java.lang.String[]
      StackMap stack:
            invokestatic java.util.Collections.emptyList:()Ljava/util/List;
            areturn
        end local 1 // java.lang.String[] rawExtensions
        end local 0 // java.lang.String extensionHeader
      LocalVariableTable:
        Start  End  Slot                 Name  Signature
            0   24     0      extensionHeader  Ljava/lang/String;
            1   24     1        rawExtensions  [Ljava/lang/String;
            3   23     2           extensions  Ljava/util/List<Lio/netty/handler/codec/http/websocketx/extensions/WebSocketExtensionData;>;
            5   20     3         rawExtension  Ljava/lang/String;
            6   20     7  extensionParameters  [Ljava/lang/String;
            7   20     8                 name  Ljava/lang/String;
            9   18     9           parameters  Ljava/util/Map<Ljava/lang/String;Ljava/lang/String;>;
           19   20     9           parameters  Ljava/util/Map<Ljava/lang/String;Ljava/lang/String;>;
           10   17    10                    i  I
           12   15    11            parameter  Ljava/lang/String;
           13   15    12     parameterMatcher  Ljava/util/regex/Matcher;
    Signature: (Ljava/lang/String;)Ljava/util/List<Lio/netty/handler/codec/http/websocketx/extensions/WebSocketExtensionData;>;
    MethodParameters:
                 Name  Flags
      extensionHeader  

  static java.lang.String appendExtension(java.lang.String, java.lang.String, java.util.Map<java.lang.String, java.lang.String>);
    descriptor: (Ljava/lang/String;Ljava/lang/String;Ljava/util/Map;)Ljava/lang/String;
    flags: (0x0008) ACC_STATIC
    Code:
      stack=4, locals=6, args_size=3
        start local 0 // java.lang.String currentHeaderValue
        start local 1 // java.lang.String extensionName
        start local 2 // java.util.Map extensionParameters
         0: .line 75
            new java.lang.StringBuilder
            dup
         1: .line 76
            aload 0 /* currentHeaderValue */
            ifnull 2
            aload 0 /* currentHeaderValue */
            invokevirtual java.lang.String.length:()I
            goto 3
      StackMap locals: java.lang.String java.lang.String java.util.Map
      StackMap stack: new 0 new 0
         2: aload 1 /* extensionName */
            invokevirtual java.lang.String.length:()I
            iconst_1
            iadd
         3: .line 75
      StackMap locals: java.lang.String java.lang.String java.util.Map
      StackMap stack: new 0 new 0 int
            invokespecial java.lang.StringBuilder.<init>:(I)V
            astore 3 /* newHeaderValue */
        start local 3 // java.lang.StringBuilder newHeaderValue
         4: .line 77
            aload 0 /* currentHeaderValue */
            ifnull 7
            aload 0 /* currentHeaderValue */
            invokevirtual java.lang.String.trim:()Ljava/lang/String;
            invokevirtual java.lang.String.isEmpty:()Z
            ifne 7
         5: .line 78
            aload 3 /* newHeaderValue */
            aload 0 /* currentHeaderValue */
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
         6: .line 79
            aload 3 /* newHeaderValue */
            ldc ","
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
         7: .line 81
      StackMap locals: java.lang.StringBuilder
      StackMap stack:
            aload 3 /* newHeaderValue */
            aload 1 /* extensionName */
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
         8: .line 82
            aload 2 /* extensionParameters */
            invokeinterface java.util.Map.entrySet:()Ljava/util/Set;
            invokeinterface java.util.Set.iterator:()Ljava/util/Iterator;
            astore 5
            goto 15
      StackMap locals: java.lang.String java.lang.String java.util.Map java.lang.StringBuilder top java.util.Iterator
      StackMap stack:
         9: aload 5
            invokeinterface java.util.Iterator.next:()Ljava/lang/Object;
            checkcast java.util.Map$Entry
            astore 4 /* extensionParameter */
        start local 4 // java.util.Map$Entry extensionParameter
        10: .line 83
            aload 3 /* newHeaderValue */
            ldc ";"
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        11: .line 84
            aload 3 /* newHeaderValue */
            aload 4 /* extensionParameter */
            invokeinterface java.util.Map$Entry.getKey:()Ljava/lang/Object;
            checkcast java.lang.String
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        12: .line 85
            aload 4 /* extensionParameter */
            invokeinterface java.util.Map$Entry.getValue:()Ljava/lang/Object;
            ifnull 15
        13: .line 86
            aload 3 /* newHeaderValue */
            bipush 61
            invokevirtual java.lang.StringBuilder.append:(C)Ljava/lang/StringBuilder;
            pop
        14: .line 87
            aload 3 /* newHeaderValue */
            aload 4 /* extensionParameter */
            invokeinterface java.util.Map$Entry.getValue:()Ljava/lang/Object;
            checkcast java.lang.String
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        end local 4 // java.util.Map$Entry extensionParameter
        15: .line 82
      StackMap locals:
      StackMap stack:
            aload 5
            invokeinterface java.util.Iterator.hasNext:()Z
            ifne 9
        16: .line 90
            aload 3 /* newHeaderValue */
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            areturn
        end local 3 // java.lang.StringBuilder newHeaderValue
        end local 2 // java.util.Map extensionParameters
        end local 1 // java.lang.String extensionName
        end local 0 // java.lang.String currentHeaderValue
      LocalVariableTable:
        Start  End  Slot                 Name  Signature
            0   17     0   currentHeaderValue  Ljava/lang/String;
            0   17     1        extensionName  Ljava/lang/String;
            0   17     2  extensionParameters  Ljava/util/Map<Ljava/lang/String;Ljava/lang/String;>;
            4   17     3       newHeaderValue  Ljava/lang/StringBuilder;
           10   15     4   extensionParameter  Ljava/util/Map$Entry<Ljava/lang/String;Ljava/lang/String;>;
    Signature: (Ljava/lang/String;Ljava/lang/String;Ljava/util/Map<Ljava/lang/String;Ljava/lang/String;>;)Ljava/lang/String;
    MethodParameters:
                     Name  Flags
      currentHeaderValue   
      extensionName        
      extensionParameters  

  private void <init>();
    descriptor: ()V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionUtil this
         0: .line 93
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 95
            return
        end local 0 // io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionUtil this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    2     0  this  Lio/netty/handler/codec/http/websocketx/extensions/WebSocketExtensionUtil;
}
SourceFile: "WebSocketExtensionUtil.java"
InnerClasses:
  public abstract Entry = java.util.Map$Entry of java.util.Map