methodwriter.java

asm的源码包 并且包含英文的文档

     * @see NOTHING
     */
    private int compute;

    /**
     * A list of labels. This list is the list of basic blocks in the method,
     * i.e. a list of Label objects linked to each other by their
     * {@link Label#successor} field, in the order they are visited by
     * {@link visitLabel}, and starting with the first basic block.
     */
    private Label labels;

    /**
     * The previous basic block.
     */
    private Label previousBlock;

    /**
     * The current basic block.
     */
    private Label currentBlock;

    /**
     * The (relative) stack size after the last visited instruction. This size
     * is relative to the beginning of the current basic block, i.e., the true
     * stack size after the last visited instruction is equal to the
     * {@link Label#inputStackTop beginStackSize} of the current basic block
     * plus <tt>stackSize</tt>.
     */
    private int stackSize;

    /**
     * The (relative) maximum stack size after the last visited instruction.
     * This size is relative to the beginning of the current basic block, i.e.,
     * the true maximum stack size after the last visited instruction is equal
     * to the {@link Label#inputStackTop beginStackSize} of the current basic
     * block plus <tt>stackSize</tt>.
     */
    private int maxStackSize;

    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------

    /**
     * Constructs a new {@link MethodWriter}.
     * 
     * @param cw the class writer in which the method must be added.
     * @param access the method's access flags (see {@link Opcodes}).
     * @param name the method's name.
     * @param desc the method's descriptor (see {@link Type}).
     * @param signature the method's signature. May be <tt>null</tt>.
     * @param exceptions the internal names of the method's exceptions. May be
     *        <tt>null</tt>.
     * @param computeMaxs <tt>true</tt> if the maximum stack size and number
     *        of local variables must be automatically computed.
     * @param computeFrames <tt>true</tt> if the stack map tables must be
     *        recomputed from scratch.
     */
    MethodWriter(
        final ClassWriter cw,
        final int access,
        final String name,
        final String desc,
        final String signature,
        final String[] exceptions,
        final boolean computeMaxs,
        final boolean computeFrames)
    {
        if (cw.firstMethod == null) {
            cw.firstMethod = this;
        } else {
            cw.lastMethod.next = this;
        }
        cw.lastMethod = this;
        this.cw = cw;
        this.access = access;
        this.name = cw.newUTF8(name);
        this.desc = cw.newUTF8(desc);
        this.descriptor = desc;
        this.signature = signature;
        if (exceptions != null && exceptions.length > 0) {
            exceptionCount = exceptions.length;
            this.exceptions = new int[exceptionCount];
            for (int i = 0; i < exceptionCount; ++i) {
                this.exceptions[i] = cw.newClass(exceptions[i]);
            }
        }
        this.compute = computeFrames ? FRAMES : (computeMaxs ? MAXS : NOTHING);
        if (computeMaxs || computeFrames) {
            if (computeFrames && name.equals("<init>")) {
                this.access |= ACC_CONSTRUCTOR;
            }
            // updates maxLocals
            int size = getArgumentsAndReturnSizes(descriptor) >> 2;
            if ((access & Opcodes.ACC_STATIC) != 0) {
                --size;
            }
            maxLocals = size;
            // creates and visits the label for the first basic block
            labels = new Label();
            labels.status |= Label.PUSHED;
            visitLabel(labels);
        }
    }

    // ------------------------------------------------------------------------
    // Implementation of the MethodVisitor interface
    // ------------------------------------------------------------------------

    public AnnotationVisitor visitAnnotationDefault() {
        annd = new ByteVector();
        return new AnnotationWriter(cw, false, annd, null, 0);
    }

    public AnnotationVisitor visitAnnotation(
        final String desc,
        final boolean visible)
    {
        ByteVector bv = new ByteVector();
        // write type, and reserve space for values count
        bv.putShort(cw.newUTF8(desc)).putShort(0);
        AnnotationWriter aw = new AnnotationWriter(cw, true, bv, bv, 2);
        if (visible) {
            aw.next = anns;
            anns = aw;
        } else {
            aw.next = ianns;
            ianns = aw;
        }
        return aw;
    }

    public AnnotationVisitor visitParameterAnnotation(
        final int parameter,
        final String desc,
        final boolean visible)
    {
        ByteVector bv = new ByteVector();
        // write type, and reserve space for values count
        bv.putShort(cw.newUTF8(desc)).putShort(0);
        AnnotationWriter aw = new AnnotationWriter(cw, true, bv, bv, 2);
        if (visible) {
            if (panns == null) {
                panns = new AnnotationWriter[Type.getArgumentTypes(descriptor).length];
            }
            aw.next = panns[parameter];
            panns[parameter] = aw;
        } else {
            if (ipanns == null) {
                ipanns = new AnnotationWriter[Type.getArgumentTypes(descriptor).length];
            }
            aw.next = ipanns[parameter];
            ipanns[parameter] = aw;
        }
        return aw;
    }

    public void visitAttribute(final Attribute attr) {
        if (attr.isCodeAttribute()) {
            attr.next = cattrs;
            cattrs = attr;
        } else {
            attr.next = attrs;
            attrs = attr;
        }
    }

    public void visitCode() {
    }

    public void visitFrame(
        final int type,
        final int nLocal,
        final Object[] local,
        final int nStack,
        final Object[] stack)
    {
        if (compute == FRAMES) {
            return;
        }

        if (type == Opcodes.F_NEW) {
            startFrame(code.length, nLocal, nStack);
            for (int i = 0; i < nLocal; ++i) {
                if (local[i] instanceof String) {
                    frame[frameIndex++] = Frame.OBJECT
                            | cw.addType((String) local[i]);
                } else if (local[i] instanceof Integer) {
                    frame[frameIndex++] = ((Integer) local[i]).intValue();
                } else {
                    frame[frameIndex++] = Frame.UNINITIALIZED
                            | cw.addUninitializedType("",
                                    ((Label) local[i]).position);
                }
            }
            for (int i = 0; i < nStack; ++i) {
                if (stack[i] instanceof String) {
                    frame[frameIndex++] = Frame.OBJECT
                            | cw.addType((String) stack[i]);
                } else if (stack[i] instanceof Integer) {
                    frame[frameIndex++] = ((Integer) stack[i]).intValue();
                } else {
                    frame[frameIndex++] = Frame.UNINITIALIZED
                            | cw.addUninitializedType("",
                                    ((Label) stack[i]).position);
                }
            }
            endFrame();
        } else {
            int delta;
            if (stackMap == null) {
                stackMap = new ByteVector();
                delta = code.length;
            } else {
                delta = code.length - previousFrameOffset - 1;
            }

            switch (type) {
                case Opcodes.F_FULL:
                    stackMap.putByte(FULL_FRAME)
                            .putShort(delta)
                            .putShort(nLocal);
                    for (int i = 0; i < nLocal; ++i) {
                        writeFrameType(local[i]);
                    }
                    stackMap.putShort(nStack);
                    for (int i = 0; i < nStack; ++i) {
                        writeFrameType(stack[i]);
                    }
                    break;
                case Opcodes.F_APPEND:
                    stackMap.putByte(SAME_FRAME_EXTENDED + nLocal)
                            .putShort(delta);
                    for (int i = 0; i < nLocal; ++i) {
                        writeFrameType(local[i]);
                    }
                    break;
                case Opcodes.F_CHOP:
                    stackMap.putByte(SAME_FRAME_EXTENDED - nLocal)
                            .putShort(delta);
                    break;
                case Opcodes.F_SAME:
                    if (delta < 64) {
                        stackMap.putByte(delta);
                    } else {
                        stackMap.putByte(SAME_FRAME_EXTENDED).putShort(delta);
                    }
                    break;
                case Opcodes.F_SAME1:
                    if (delta < 64) {
                        stackMap.putByte(SAME_LOCALS_1_STACK_ITEM_FRAME + delta);
                    } else {
                        stackMap.putByte(SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED)
                                .putShort(delta);
                    }
                    writeFrameType(stack[0]);
                    break;
            }

            previousFrameOffset = code.length;
            ++frameCount;
        }
    }

    public void visitInsn(final int opcode) {
        // adds the instruction to the bytecode of the method
        code.putByte(opcode);
        // update currentBlock
        // Label currentBlock = this.currentBlock;
        if (currentBlock != null) {
            if (compute == FRAMES) {
                currentBlock.frame.execute(opcode, 0, null, null);
            } else {
                // updates current and max stack sizes
                int size = stackSize + Frame.SIZE[opcode];
                if (size > maxStackSize) {
                    maxStackSize = size;
                }
                stackSize = size;
            }
            // if opcode == ATHROW or xRETURN, ends current block (no successor)
            if ((opcode >= Opcodes.IRETURN && opcode <= Opcodes.RETURN)
                    || opcode == Opcodes.ATHROW)
            {
                noSuccessor();
            }
        }
    }

    public void visitIntInsn(final int opcode, final int operand) {
        // Label currentBlock = this.currentBlock;
        if (currentBlock != null) {
            if (compute == FRAMES) {
                currentBlock.frame.execute(opcode, operand, null, null);
            } else if (opcode != Opcodes.NEWARRAY) {
                // updates current and max stack sizes only for NEWARRAY
                // (stack size variation = 0 for BIPUSH or SIPUSH)
                int size = stackSize + 1;
                if (size > maxStackSize) {
                    maxStackSize = size;
                }
                stackSize = size;
            }
        }
        // adds the instruction to the bytecode of the method
        if (opcode == Opcodes.SIPUSH) {
            code.put12(opcode, operand);
        } else { // BIPUSH or NEWARRAY
            code.put11(opcode, operand);
        }
    }

    public void visitVarInsn(final int opcode, final int var) {
        // Label currentBlock = this.currentBlock;
        if (currentBlock != null) {
            if (compute == FRAMES) {
                currentBlock.frame.execute(opcode, var, null, null);
            } else {
                // updates current and max stack sizes
                if (opcode == Opcodes.RET) {
                    // no stack change, but end of current block (no successor)
                    currentBlock.status |= Label.RET;
                    // save 'stackSize' here for future use
                    // (see {@link #findSubroutineSuccessors})
                    currentBlock.inputStackTop = stackSize;
                    noSuccessor();
                } else { // xLOAD or xSTORE
                    int size = stackSize + Frame.SIZE[opcode];
                    if (size > maxStackSize) {
                        maxStackSize = size;
                    }
                    stackSize = size;
                }
            }
        }
        if (compute != NOTHING) {
            // updates max locals
            int n;
            if (opcode == Opcodes.LLOAD || opcode == Opcodes.DLOAD
                    || opcode == Opcodes.LSTORE || opcode == Opcodes.DSTORE)
            {
                n = var + 2;
            } else {
                n = var + 1;
            }