/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF 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 org.apache.myfaces.config.annotation;

 import java.io.DataInput;

 import java.io.IOException;

 import java.util.Set;

 import java.util.logging.Level;

 import java.util.logging.Logger;

 /**

  * Scan .class files for annotation signature directly, without load them.

  * 

  * @since 2.0

  * @author Leonardo Uribe (latest modification by $Author$)

  * @version $Revision$ $Date$

  */

 class _ClassByteCodeAnnotationFilter

 {

     private static final Logger log = Logger.getLogger(_ClassByteCodeAnnotationFilter.class.getName());

     //Constants used to define type in cp_info structure

     private static final int CP_INFO_CLASS = 7;

     private static final int CP_INFO_FIELD_REF = 9;

     private static final int CP_INFO_METHOD_REF = 10;

     private static final int CP_INFO_INTERFACE_REF = 11;

     private static final int CP_INFO_STRING = 8;

     private static final int CP_INFO_INTEGER = 3;

     private static final int CP_INFO_FLOAT = 4;

     private static final int CP_INFO_LONG = 5;

     private static final int CP_INFO_DOUBLE = 6;

     private static final int CP_INFO_NAME_AND_TYPE = 12;

     private static final int CP_INFO_UTF8 = 1;

     private static final int CP_INFO_METHOD_HANDLE = 15;

     private static final int CP_INFO_METHOD_TYPE = 16;

     private static final int CP_INFO_INVOKE_DYNAMIC = 18;

     /**

      * Checks if the .class file referenced by the DataInput could 

      * contain the annotation names available in the set.

      * 

      * @param in

      * @param byteCodeAnnotationsNames

      * @return

      * @throws IOException

      */

     public boolean couldContainAnnotationsOnClassDef(DataInput in,

             Set<String> byteCodeAnnotationsNames)

         throws IOException

     {

         /* According to Java VM Spec, each .class file contains

          * a single class or interface definition. The structure

          * definition is shown below:

     ClassFile {

         u4 magic;

         u2 minor_version;

         u2 major_version;

         u2 constant_pool_count;

         cp_info constant_pool[constant_pool_count-1];

         u2 access_flags;

         u2 this_class;

         u2 super_class;

         u2 interfaces_count;

         u2 interfaces[interfaces_count];

         u2 fields_count;

         field_info fields[fields_count];

         u2 methods_count;

         method_info methods[methods_count];

         u2 attributes_count;

         attribute_info attributes[attributes_count];

     }

         * u1 = readUnsignedByte 

         * u2 = readUnsignedShort

         * u4 = readInt

         *   

         */

         int magic = in.readInt(); //u4

         if (magic != 0xCAFEBABE)

         {

             //the file is not recognized as a class file 

             return false;

         }

         //u2 but since in java does not exists unsigned,

         //store on a bigger value

         int minorVersion = in.readUnsignedShort();//u2

         int majorVersion = in.readUnsignedShort();//u2

         if (majorVersion < 49)

         {

             //Compiled with jdk 1.4, so does not have annotations

             return false;

         }

         //constantsPoolCount is the number of entries + 1

         //The index goes from 1 to constantsPoolCount-1

         int constantsPoolCount = in.readUnsignedShort();

         for (int i = 1; i < constantsPoolCount; i++)

         {

             // Format:

             // cp_info {

             //     u1 tag;

             //     u1 info[];

             // }

             int tag = in.readUnsignedByte();

             switch (tag)

             {

                 case CP_INFO_UTF8:

                     //u2 length

                     //u1 bytes[length]

                     //Check if the string is a annotation reference

                     //name

                     String name = in.readUTF();

                     if (byteCodeAnnotationsNames.contains(name))

                     {

                         return true;

                     }

                     break;

                 case CP_INFO_CLASS: //ignore

                     //u2 name_index

                     in.readUnsignedShort();

                     break;

                 case CP_INFO_FIELD_REF: //ignore

                 case CP_INFO_METHOD_REF: //ignore

                 case CP_INFO_INTERFACE_REF: //ignore

                     //u2 class_index

                     //u2 name_and_type_index

                     in.readUnsignedShort();

                     in.readUnsignedShort();

                     break;

                 case CP_INFO_STRING: //ignore

                     //u2 string_index

                     in.readUnsignedShort();

                     break;

                 case CP_INFO_INTEGER: //ignore

                 case CP_INFO_FLOAT: //ignore

                     //u4 bytes

                     in.readInt();

                     break;

                 case CP_INFO_LONG: //ignore

                 case CP_INFO_DOUBLE: //ignore

                     //u4 high_bytes

                     //u4 low_bytes

                     in.readInt();

                     in.readInt();

                     // this tag takes two entries in the constants pool

                     i++;

                     break;

                 case CP_INFO_NAME_AND_TYPE: //ignore

                     //u2 name_index

                     //u2 descriptor_index

                     in.readUnsignedShort();

                     in.readUnsignedShort();

                     break;

                 case CP_INFO_METHOD_HANDLE:     // Ignore

                     // u1 reference_kind

                     // u2 reference_index

                     in.readUnsignedByte();

                     in.readUnsignedShort();

                     break;

                 case CP_INFO_METHOD_TYPE:       // Ignore

                     // u2 descriptor_index

                     in.readUnsignedShort();

                     break;

                 case CP_INFO_INVOKE_DYNAMIC:    // Ignore

                     // u2 bootstrap_method_attr_index;

                     // u2 name_and_type_index;

                     in.readUnsignedShort();

                     in.readUnsignedShort();

                     break;

                 default:

                     // THIS SHOULD NOT HAPPEN! Log error info

                     // and break for loop, because from this point

                     // we are reading corrupt data.

                     if (log.isLoggable(Level.WARNING))

                     {

                         log.warning("Unknown tag in constants pool: " + tag);

                     }

                     i = constantsPoolCount;

                     break;

             }

         }

         return false;

     }

 }