analyzer.java

asm的源码包 并且包含英文的文档

                                        || insnOpcode == DSTORE)
                                {
                                    subroutine.access[var + 1] = true;
                                }
                            } else if (insnNode instanceof IincInsnNode) {
                                int var = ((IincInsnNode) insnNode).var;
                                subroutine.access[var] = true;
                            }
                        }
                        merge(insn + 1, current, subroutine);
                        newControlFlowEdge(insn, insn + 1);
                    }
                }

                List insnHandlers = handlers[insn];
                if (insnHandlers != null) {
                    for (int i = 0; i < insnHandlers.size(); ++i) {
                        TryCatchBlockNode tcb = (TryCatchBlockNode) insnHandlers.get(i);
                        Type type;
                        if (tcb.type == null) {
                            type = Type.getObjectType("java/lang/Throwable");
                        } else {
                            type = Type.getObjectType(tcb.type);
                        }
                        int jump = insns.indexOf(tcb.handler);
                        if (newControlFlowExceptionEdge(insn, jump)) {
                            handler.init(f);
                            handler.clearStack();
                            handler.push(interpreter.newValue(type));
                            merge(jump, handler, subroutine);
                        }
                    }
                }
            } catch (AnalyzerException e) {
                throw new AnalyzerException("Error at instruction " + insn
                        + ": " + e.getMessage(), e);
            } catch (Exception e) {
                throw new AnalyzerException("Error at instruction " + insn
                        + ": " + e.getMessage(), e);
            }
        }

        return frames;
    }

    private void findSubroutine(int insn, final Subroutine sub, final List calls)
            throws AnalyzerException
    {
        while (true) {
            if (insn < 0 || insn >= n) {
                throw new AnalyzerException("Execution can fall off end of the code");
            }
            if (subroutines[insn] != null) {
                return;
            }
            subroutines[insn] = sub.copy();
            AbstractInsnNode node = insns.get(insn);

            // calls findSubroutine recursively on normal successors
            if (node instanceof JumpInsnNode) {
                if (node.getOpcode() == JSR) {
                    // do not follow a JSR, it leads to another subroutine!
                    calls.add(node);
                } else {
                    JumpInsnNode jnode = (JumpInsnNode) node;
                    findSubroutine(insns.indexOf(jnode.label), sub, calls);
                }
            } else if (node instanceof TableSwitchInsnNode) {
                TableSwitchInsnNode tsnode = (TableSwitchInsnNode) node;
                findSubroutine(insns.indexOf(tsnode.dflt), sub, calls);
                for (int i = tsnode.labels.size() - 1; i >= 0; --i) {
                    LabelNode l = (LabelNode) tsnode.labels.get(i);
                    findSubroutine(insns.indexOf(l), sub, calls);
                }
            } else if (node instanceof LookupSwitchInsnNode) {
                LookupSwitchInsnNode lsnode = (LookupSwitchInsnNode) node;
                findSubroutine(insns.indexOf(lsnode.dflt), sub, calls);
                for (int i = lsnode.labels.size() - 1; i >= 0; --i) {
                    LabelNode l = (LabelNode) lsnode.labels.get(i);
                    findSubroutine(insns.indexOf(l), sub, calls);
                }
            }

            // calls findSubroutine recursively on exception handler successors
            List insnHandlers = handlers[insn];
            if (insnHandlers != null) {
                for (int i = 0; i < insnHandlers.size(); ++i) {
                    TryCatchBlockNode tcb = (TryCatchBlockNode) insnHandlers.get(i);
                    findSubroutine(insns.indexOf(tcb.handler), sub, calls);
                }
            }

            // if insn does not falls through to the next instruction, return.
            switch (node.getOpcode()) {
                case GOTO:
                case RET:
                case TABLESWITCH:
                case LOOKUPSWITCH:
                case IRETURN:
                case LRETURN:
                case FRETURN:
                case DRETURN:
                case ARETURN:
                case RETURN:
                case ATHROW:
                    return;
            }
            insn++;
        }
    }

    /**
     * Returns the symbolic stack frame for each instruction of the last
     * recently analyzed method.
     * 
     * @return the symbolic state of the execution stack frame at each bytecode
     *         instruction of the method. The size of the returned array is
     *         equal to the number of instructions (and labels) of the method. A
     *         given frame is <tt>null</tt> if the corresponding instruction
     *         cannot be reached, or if an error occured during the analysis of
     *         the method.
     */
    public Frame[] getFrames() {
        return frames;
    }

    /**
     * Returns the exception handlers for the given instruction.
     * 
     * @param insn the index of an instruction of the last recently analyzed
     *        method.
     * @return a list of {@link TryCatchBlockNode} objects.
     */
    public List getHandlers(final int insn) {
        return handlers[insn];
    }

    /**
     * Constructs a new frame with the given size.
     * 
     * @param nLocals the maximum number of local variables of the frame.
     * @param nStack the maximum stack size of the frame.
     * @return the created frame.
     */
    protected Frame newFrame(final int nLocals, final int nStack) {
        return new Frame(nLocals, nStack);
    }

    /**
     * Constructs a new frame that is identical to the given frame.
     * 
     * @param src a frame.
     * @return the created frame.
     */
    protected Frame newFrame(final Frame src) {
        return new Frame(src);
    }

    /**
     * Creates a control flow graph edge. The default implementation of this
     * method does nothing. It can be overriden in order to construct the
     * control flow graph of a method (this method is called by the
     * {@link #analyze analyze} method during its visit of the method's code).
     * 
     * @param insn an instruction index.
     * @param successor index of a successor instruction.
     */
    protected void newControlFlowEdge(final int insn, final int successor) {
    }

    /**
     * Creates a control flow graph edge corresponding to an exception handler.
     * The default implementation of this method does nothing. It can be
     * overriden in order to construct the control flow graph of a method (this
     * method is called by the {@link #analyze analyze} method during its visit
     * of the method's code).
     * 
     * @param insn an instruction index.
     * @param successor index of a successor instruction.
     * @return true if this edge must be considered in the data flow analysis
     *         performed by this analyzer, or false otherwise. The default
     *         implementation of this method always returns true.
     */
    protected boolean newControlFlowExceptionEdge(
        final int insn,
        final int successor)
    {
        return true;
    }

    // -------------------------------------------------------------------------

    private void merge(
        final int insn,
        final Frame frame,
        final Subroutine subroutine) throws AnalyzerException
    {
        Frame oldFrame = frames[insn];
        Subroutine oldSubroutine = subroutines[insn];
        boolean changes = false;

        if (oldFrame == null) {
            frames[insn] = newFrame(frame);
            changes = true;
        } else {
            changes |= oldFrame.merge(frame, interpreter);
        }

        if (oldSubroutine == null) {
            if (subroutine != null) {
                subroutines[insn] = subroutine.copy();
                changes = true;
            }
        } else {
            if (subroutine != null) {
                changes |= oldSubroutine.merge(subroutine);
            }
        }
        if (changes && !queued[insn]) {
            queued[insn] = true;
            queue[top++] = insn;
        }
    }

    private void merge(
        final int insn,
        final Frame beforeJSR,
        final Frame afterRET,
        final Subroutine subroutineBeforeJSR,
        final boolean[] access) throws AnalyzerException
    {
        Frame oldFrame = frames[insn];
        Subroutine oldSubroutine = subroutines[insn];
        boolean changes = false;

        afterRET.merge(beforeJSR, access);

        if (oldFrame == null) {
            frames[insn] = newFrame(afterRET);
            changes = true;
        } else {
            changes |= oldFrame.merge(afterRET, access);
        }

        if (oldSubroutine != null && subroutineBeforeJSR != null) {
            changes |= oldSubroutine.merge(subroutineBeforeJSR);
        }
        if (changes && !queued[insn]) {
            queued[insn] = true;
            queue[top++] = insn;
        }
    }
}