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      1 /*
      2  * Copyright (C) 2007 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.dx.dex.file;
     18 
     19 import com.android.dx.util.AnnotatedOutput;
     20 
     21 /**
     22  * Base class for any structurally-significant and (potentially)
     23  * repeated piece of a Dalvik file.
     24  */
     25 public abstract class Item {
     26     /**
     27      * Constructs an instance.
     28      */
     29     public Item() {
     30         // This space intentionally left blank.
     31     }
     32 
     33     /**
     34      * Returns the item type for this instance.
     35      *
     36      * @return {@code non-null;} the item type
     37      */
     38     public abstract ItemType itemType();
     39 
     40     /**
     41      * Returns the human name for the particular type of item this
     42      * instance is.
     43      *
     44      * @return {@code non-null;} the name
     45      */
     46     public final String typeName() {
     47         return itemType().toHuman();
     48     }
     49 
     50     /**
     51      * Gets the size of this instance when written, in bytes.
     52      *
     53      * @return {@code >= 0;} the write size
     54      */
     55     public abstract int writeSize();
     56 
     57     /**
     58      * Populates a {@link DexFile} with items from within this instance.
     59      * This will <i>not</i> add an item to the file for this instance itself
     60      * (which should have been done by whatever refers to this instance).
     61      *
     62      * <p><b>Note:</b> Subclasses must override this to do something
     63      * appropriate.</p>
     64      *
     65      * @param file {@code non-null;} the file to populate
     66      */
     67     public abstract void addContents(DexFile file);
     68 
     69     /**
     70      * Writes the representation of this instance to the given data section,
     71      * using the given {@link DexFile} to look things up as needed.
     72      * If this instance keeps track of its offset, then this method will
     73      * note the written offset and will also throw an exception if this
     74      * instance has already been written.
     75      *
     76      * @param file {@code non-null;} the file to use for reference
     77      * @param out {@code non-null;} where to write to
     78      */
     79     public abstract void writeTo(DexFile file, AnnotatedOutput out);
     80 }
     81