classwriter.java

asm的源码包 并且包含英文的文档

     */
    Item newMethodItem(
        final String owner,
        final String name,
        final String desc,
        final boolean itf)
    {
        int type = itf ? IMETH : METH;
        key3.set(type, owner, name, desc);
        Item result = get(key3);
        if (result == null) {
            put122(type, newClass(owner), newNameType(name, desc));
            result = new Item(index++, key3);
            put(result);
        }
        return result;
    }

    /**
     * Adds a method reference to the constant pool of the class being build.
     * Does nothing if the constant pool already contains a similar item.
     * <i>This method is intended for {@link Attribute} sub classes, and is
     * normally not needed by class generators or adapters.</i>
     * 
     * @param owner the internal name of the method's owner class.
     * @param name the method's name.
     * @param desc the method's descriptor.
     * @param itf <tt>true</tt> if <tt>owner</tt> is an interface.
     * @return the index of a new or already existing method reference item.
     */
    public int newMethod(
        final String owner,
        final String name,
        final String desc,
        final boolean itf)
    {
        return newMethodItem(owner, name, desc, itf).index;
    }

    /**
     * Adds an integer to the constant pool of the class being build. Does
     * nothing if the constant pool already contains a similar item.
     * 
     * @param value the int value.
     * @return a new or already existing int item.
     */
    Item newInteger(final int value) {
        key.set(value);
        Item result = get(key);
        if (result == null) {
            pool.putByte(INT).putInt(value);
            result = new Item(index++, key);
            put(result);
        }
        return result;
    }

    /**
     * Adds a float to the constant pool of the class being build. Does nothing
     * if the constant pool already contains a similar item.
     * 
     * @param value the float value.
     * @return a new or already existing float item.
     */
    Item newFloat(final float value) {
        key.set(value);
        Item result = get(key);
        if (result == null) {
            pool.putByte(FLOAT).putInt(key.intVal);
            result = new Item(index++, key);
            put(result);
        }
        return result;
    }

    /**
     * Adds a long to the constant pool of the class being build. Does nothing
     * if the constant pool already contains a similar item.
     * 
     * @param value the long value.
     * @return a new or already existing long item.
     */
    Item newLong(final long value) {
        key.set(value);
        Item result = get(key);
        if (result == null) {
            pool.putByte(LONG).putLong(value);
            result = new Item(index, key);
            put(result);
            index += 2;
        }
        return result;
    }

    /**
     * Adds a double to the constant pool of the class being build. Does nothing
     * if the constant pool already contains a similar item.
     * 
     * @param value the double value.
     * @return a new or already existing double item.
     */
    Item newDouble(final double value) {
        key.set(value);
        Item result = get(key);
        if (result == null) {
            pool.putByte(DOUBLE).putLong(key.longVal);
            result = new Item(index, key);
            put(result);
            index += 2;
        }
        return result;
    }

    /**
     * Adds a string to the constant pool of the class being build. Does nothing
     * if the constant pool already contains a similar item.
     * 
     * @param value the String value.
     * @return a new or already existing string item.
     */
    private Item newString(final String value) {
        key2.set(STR, value, null, null);
        Item result = get(key2);
        if (result == null) {
            pool.put12(STR, newUTF8(value));
            result = new Item(index++, key2);
            put(result);
        }
        return result;
    }

    /**
     * Adds a name and type to the constant pool of the class being build. Does
     * nothing if the constant pool already contains a similar item. <i>This
     * method is intended for {@link Attribute} sub classes, and is normally not
     * needed by class generators or adapters.</i>
     * 
     * @param name a name.
     * @param desc a type descriptor.
     * @return the index of a new or already existing name and type item.
     */
    public int newNameType(final String name, final String desc) {
        key2.set(NAME_TYPE, name, desc, null);
        Item result = get(key2);
        if (result == null) {
            put122(NAME_TYPE, newUTF8(name), newUTF8(desc));
            result = new Item(index++, key2);
            put(result);
        }
        return result.index;
    }

    /**
     * Adds the given internal name to {@link #typeTable} and returns its index.
     * Does nothing if the type table already contains this internal name.
     * 
     * @param type the internal name to be added to the type table.
     * @return the index of this internal name in the type table.
     */
    int addType(final String type) {
        key.set(TYPE_NORMAL, type, null, null);
        Item result = get(key);
        if (result == null) {
            result = addType(key);
        }
        return result.index;
    }

    /**
     * Adds the given "uninitialized" type to {@link #typeTable} and returns its
     * index. This method is used for UNINITIALIZED types, made of an internal
     * name and a bytecode offset.
     * 
     * @param type the internal name to be added to the type table.
     * @param offset the bytecode offset of the NEW instruction that created
     *        this UNINITIALIZED type value.
     * @return the index of this internal name in the type table.
     */
    int addUninitializedType(final String type, final int offset) {
        key.type = TYPE_UNINIT;
        key.intVal = offset;
        key.strVal1 = type;
        key.hashCode = 0x7FFFFFFF & (TYPE_UNINIT + type.hashCode() + offset);
        Item result = get(key);
        if (result == null) {
            result = addType(key);
        }
        return result.index;
    }

    /**
     * Adds the given Item to {@link #typeTable}.
     * 
     * @param item the value to be added to the type table.
     * @return the added Item, which a new Item instance with the same value as
     *         the given Item.
     */
    private Item addType(final Item item) {
        ++typeCount;
        Item result = new Item(typeCount, key);
        put(result);
        if (typeTable == null) {
            typeTable = new Item[16];
        }
        if (typeCount == typeTable.length) {
            Item[] newTable = new Item[2 * typeTable.length];
            System.arraycopy(typeTable, 0, newTable, 0, typeTable.length);
            typeTable = newTable;
        }
        typeTable[typeCount] = result;
        return result;
    }

    /**
     * Returns the index of the common super type of the two given types. This
     * method calls {@link #getCommonSuperClass} and caches the result in the
     * {@link #items} hash table to speedup future calls with the same
     * parameters.
     * 
     * @param type1 index of an internal name in {@link #typeTable}.
     * @param type2 index of an internal name in {@link #typeTable}.
     * @return the index of the common super type of the two given types.
     */
    int getMergedType(final int type1, final int type2) {
        key2.type = TYPE_MERGED;
        key2.longVal = type1 | (((long) type2) << 32);
        key2.hashCode = 0x7FFFFFFF & (TYPE_MERGED + type1 + type2);
        Item result = get(key2);
        if (result == null) {
            String t = typeTable[type1].strVal1;
            String u = typeTable[type2].strVal1;
            key2.intVal = addType(getCommonSuperClass(t, u));
            result = new Item((short) 0, key2);
            put(result);
        }
        return result.intVal;
    }

    /**
     * Returns the common super type of the two given types. The default
     * implementation of this method <i>loads<i> the two given classes and uses
     * the java.lang.Class methods to find the common super class. It can be
     * overriden to compute this common super type in other ways, in particular
     * without actually loading any class, or to take into account the class
     * that is currently being generated by this ClassWriter, which can of
     * course not be loaded since it is under construction.
     * 
     * @param type1 the internal name of a class.
     * @param type2 the internal name of another class.
     * @return the internal name of the common super class of the two given
     *         classes.
     */
    protected String getCommonSuperClass(final String type1, final String type2)
    {
        Class c, d;
        try {
            c = Class.forName(type1.replace('/', '.'));
            d = Class.forName(type2.replace('/', '.'));
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
        if (c.isAssignableFrom(d)) {
            return type1;
        }
        if (d.isAssignableFrom(c)) {
            return type2;
        }
        if (c.isInterface() || d.isInterface()) {
            return "java/lang/Object";
        } else {
            do {
                c = c.getSuperclass();
            } while (!c.isAssignableFrom(d));
            return c.getName().replace('.', '/');
        }
    }

    /**
     * Returns the constant pool's hash table item which is equal to the given
     * item.
     * 
     * @param key a constant pool item.
     * @return the constant pool's hash table item which is equal to the given
     *         item, or <tt>null</tt> if there is no such item.
     */
    private Item get(final Item key) {
        Item i = items[key.hashCode % items.length];
        while (i != null && !key.isEqualTo(i)) {
            i = i.next;
        }
        return i;
    }

    /**
     * Puts the given item in the constant pool's hash table. The hash table
     * <i>must</i> not already contains this item.
     * 
     * @param i the item to be added to the constant pool's hash table.
     */
    private void put(final Item i) {
        if (index > threshold) {
            int ll = items.length;
            int nl = ll * 2 + 1;
            Item[] newItems = new Item[nl];
            for (int l = ll - 1; l >= 0; --l) {
                Item j = items[l];
                while (j != null) {
                    int index = j.hashCode % newItems.length;
                    Item k = j.next;
                    j.next = newItems[index];
                    newItems[index] = j;
                    j = k;
                }
            }
            items = newItems;
            threshold = (int) (nl * 0.75);
        }
        int index = i.hashCode % items.length;
        i.next = items[index];
        items[index] = i;
    }

    /**
     * Puts one byte and two shorts into the constant pool.
     * 
     * @param b a byte.
     * @param s1 a short.
     * @param s2 another short.
     */
    private void put122(final int b, final int s1, final int s2) {
        pool.put12(b, s1).putShort(s2);
    }
}