Interface MethodBuilder

All Known Implementing Classes:
BCMethod

public interface MethodBuilder
MethodBuilder is used to generate the code for a method.

The code for a method is built in a way that corresponds to the layout of the stack machine that is the Java Virtual Machine. Values are pushed on the stack, moved about on the stack and then popped off the stack by operations such as method calls. An understanding of hoe the JVM operates is useful before using this class.

All the method descriptions below are generating bytecode to achieved the desired behaviour when the generated class is loaded. None of this class's methods calls actually invoke methods or create objects described by the callers.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addThrownException(String exceptionClass)
    Declare the method throws an exception.
    int
    callMethod(short type, String declaringClass, String methodName, String returnType, int numArgs)
    Call a method.
    int
    callMethod(Object methodDescriptor)
    Call a method previously described by describeMethod().
    void
    Call super().
    void
    cast(String className)
    Cast the top stack value.
    void
    Indicate the method is complete.
    void
    Complete a conditional which completes the false code path.
    void
    Initiate a conditional sequence.
    void
    Initiate a conditional sequence.
    describeMethod(short opcode, String declaringClass, String methodName, String returnType)
    Return an object that efficiently (to the implementation) describes a zero-argument method and can be used with the single argument callMethod().
    void
    dup()
    Duplicate the top value on the stack.
    void
    End a statement.
    void
    getArrayElement(int element)
    Pop an array refrence off the stack and push an element from that array.
    void
    getField(String declaringClass, String fieldName, String fieldType)
    Push the contents of the described field onto the stack.
    void
    Push the contents of the local field onto the stack.
    return the name of the method.
    void
    getParameter(int id)
    Push a parameter value.
    void
    getStaticField(String declaringClass, String fieldName, String fieldType)
    Push the contents of the described static field onto the stack.
    void
    isInstanceOf(String className)
    Pop the top stack value and push a boolean that is the result of an instanceof check on the popped reference.
    void
    Return from a method, optionally with a value.
    void
    pop()
    Pop the top value off the stack
    void
    push(boolean value)
    Push a boolean constant onto the stack
    void
    push(byte value)
    Push a byte constant onto the stack
    void
    push(double value)
    Push a double constant onto the stack
    void
    push(float value)
    Push a float constant onto the stack
    void
    push(int value)
    Push a int constant onto the stack
    void
    push(long value)
    Push a long constant onto the stack
    void
    push(short value)
    Push a short constant onto the stack
    void
    push(String value)
    Push a String constant onto the stack
    void
    pushNewArray(String className, int size)
    Create an instance of an array and push it onto the stack.
    void
    pushNewComplete(int numArgs)
    Complete the sequence that was started with pushNewStart().
    void
    pushNewStart(String className)
    Initiate a sequence that calls a constructor, equivalent to the new operator in Java.
    void
    pushNull(String className)
    Push a typed null onto the stack
    void
    Push this onto the stack.
    void
    putField(String fieldName, String fieldType)
    Pop the top stack value and store it in the instance field of this class.
    void
    putField(String declaringClass, String fieldName, String fieldType)
    Pop the top stack value and store it in the field.
    void
    Pop the top stack value and store it in the local field.
    void
    setArrayElement(int element)
    Pop an array reference off the stack, store a value in the array at the passed in offset.
    void
    Pop the top stack value and store it in the local field.
    void
    Complete the true code path of a conditional.
    boolean
    statementNumHitLimit(int noStatementsAdded)
    Tell if statement number in this method builder hits limit.
    void
    Swap the top two values on the stack.
    void
    upCast(String className)
    Upcast the top stack value.
  • Method Details

    • addThrownException

      void addThrownException(String exceptionClass)
      Declare the method throws an exception. Must be called before any code is added to the method.
    • getName

      String getName()
      return the name of the method.
    • complete

      void complete()
      Indicate the method is complete. Once this call has been made the caller must discard the reference to this object.
    • getParameter

      void getParameter(int id)
      Push a parameter value.
                      Stack ...  =>
                            ...,param_value
                      
      Parameters:
      id - position of the parameter (zero based).
    • push

      void push(byte value)
      Push a byte constant onto the stack
                      Stack ...  =>
                            ...,byte_value
                      
    • push

      void push(boolean value)
      Push a boolean constant onto the stack
                      Stack ...  =>
                            ...,boolean_value
                      
    • push

      void push(short value)
      Push a short constant onto the stack
                      Stack ...  =>
                            ...,short_value
                      
    • push

      void push(int value)
      Push a int constant onto the stack
                      Stack ...  =>
                            ...,int_value
                      
    • push

      void push(long value)
      Push a long constant onto the stack
                      Stack ...  =>
                            ...,long_value
                      
    • push

      void push(float value)
      Push a float constant onto the stack
                      Stack ...  =>
                            ...,float_value
                      
    • push

      void push(double value)
      Push a double constant onto the stack
                      Stack ...  =>
                            ...,double_value
                      
    • push

      void push(String value)
      Push a String constant onto the stack
                      Stack ...  =>
                            ...,String_value
                      
    • pushNull

      void pushNull(String className)
      Push a typed null onto the stack
                      Stack ...  =>
                            ...,null
                      
    • getField

      void getField(LocalField field)
      Push the contents of the local field onto the stack. This call pushes the this instance required to access the field itself.
                      Stack ...  =>
                            ...,field_value
                      
    • getField

      void getField(String declaringClass, String fieldName, String fieldType)
      Push the contents of the described field onto the stack. This call requires the instance (reference) to be pushed by the caller.
                      Stack ...,field_ref  =>
                            ...,field_value
                      
    • getStaticField

      void getStaticField(String declaringClass, String fieldName, String fieldType)
      Push the contents of the described static field onto the stack.
                      Stack ...  =>
                            ...,field_value
                      
    • setField

      void setField(LocalField field)
      Pop the top stack value and store it in the local field. This call pushes the this instance required to access the field itself. This call does not leave any value on the stack.
              Stack ...,value  =>
                    ...
              
    • putField

      void putField(LocalField field)
      Pop the top stack value and store it in the local field. This call pushes the this instance required to access the field itself. Like the Java language 'field = value', this leaves the value on the stack.
                      Stack ...,value  =>
                            ...,value
                      
    • putField

      void putField(String fieldName, String fieldType)
      Pop the top stack value and store it in the instance field of this class. This call pushes the this instance required to access the field itself. Like the Java language 'field = value', this leaves the value on the stack.
                      Stack ...,value  =>
                            ...,value
                      
    • putField

      void putField(String declaringClass, String fieldName, String fieldType)
      Pop the top stack value and store it in the field. This call requires the instance to be pushed by the caller. Like the Java language 'field = value', this leaves the value on the stack.
                      Stack ...,field_ref,value  =>
                            ...,value
                      
    • pushNewStart

      void pushNewStart(String className)
      Initiate a sequence that calls a constructor, equivalent to the new operator in Java. After this call, the caller must push any arguments and then complete the construction with a call to pushNewComplete(). Only arguments to the constructor can be pushed onto the stack between the pushNewStart() and pushNewComplete() method calls.
                      Stack ... => [unchanged]
                            ...
                      
      Parameters:
      className - class name of object to be created.
    • pushNewComplete

      void pushNewComplete(int numArgs)
      Complete the sequence that was started with pushNewStart(). Pop the arguments to the constructor and push the reference to the newly created object.
                      Stack ...,value* => [numArgs number of values will be popped]
                            ...,new_ref
                      
      Parameters:
      numArgs - number of arguments to the constructor (can be 0).
    • pushNewArray

      void pushNewArray(String className, int size)
      Create an instance of an array and push it onto the stack.
                      Stack ...  =>
                            ...,array_ref
                      
      Parameters:
      className - - type of array.
      size - - number of elements in the array
    • pushThis

      void pushThis()
      Push this onto the stack.
                      Stack ...  =>
                            ...,this_ref
                      
    • upCast

      void upCast(String className)
      Upcast the top stack value. This is used for correct method resolution by upcasting method parameters. It does not put any casting code into the byte code stream. Can only be used for refrences.
                      Stack ...,ref =>
                            ...,ref
                      
    • cast

      void cast(String className)
      Cast the top stack value. Correctly down-casts a reference or casts a primitive type (e.g. int to short).
                      Stack ...,value =>
                            ...,cast_value
                      
      Parameters:
      className - type (primitive, interface or class) to cast to.
    • isInstanceOf

      void isInstanceOf(String className)
      Pop the top stack value and push a boolean that is the result of an instanceof check on the popped reference.
                      Stack ...,ref =>
                            ...,boolean_value
                      
      .
    • pop

      void pop()
      Pop the top value off the stack
                      Stack ..., value =>
                            ...
                      
      .
    • endStatement

      void endStatement()
      End a statement. Pops the top-word of the stack, if any. Must only be called if zero or one item exists on the stack.
                      Stack value =>
                            :empty:
                      or
      
                      Stack :empty: =>
                            :empty:
      
                      
      .
    • methodReturn

      void methodReturn()
      Return from a method, optionally with a value. Must only be called if zero or one item exists on the stack. If the stack contains a single value then that is popped and used as the returned value.
                      Stack value =>
                            :empty:
                      or
      
                      Stack :empty: =>
                            :empty:
      
                      
      .
    • conditionalIfNull

      void conditionalIfNull()
      Initiate a conditional sequence. The top value on the stack (a reference) is popped and compared to 'null'. If the value is null then the code following this call until the startElseCode() will be executed at runtime, otherwise the code following startElseCode() until the completeConditional() is called.
      E.g.
                      mb.callMethod(...); // pushes an object onto the stack
                      mb.conditionalIfNull();
                        mb.push(3);
                      mb.startElseCode();
                        mb.push(5);
                      mb.completeConditional();
                      // at this point 3 or 5 will be on the stack
                      
      Each path through the ?: statement must leave the stack at the same depth as the other.
      If the if or else code pops values from the stack that were before the conditional value, then they must use the same number of values from the stack.
                      Stack ...,ref =>
                            ...
                      
      .
    • conditionalIf

      void conditionalIf()
      Initiate a conditional sequence. The top value on the stack must be a boolean and will be popped. If it is true then the code following this call until the startElseCode() will be executed at runtime, otherwise the code following startElseCode() until the completeConditional() is called. See conditionalIfNull() for example and restrictions.
                      Stack ...,boolean_value =>
                            ...
                      
      .
    • startElseCode

      void startElseCode()
      Complete the true code path of a conditional.
    • completeConditional

      void completeConditional()
      Complete a conditional which completes the false code path.
    • callMethod

      int callMethod(short type, String declaringClass, String methodName, String returnType, int numArgs)
      Call a method. The instance (receiver or reference) for non-static methods must be pushed by the caller. The instance (for non-static) and the arguments are popped of the stack, and the return value (if any) is pushed onto the stack.
      The type needs to be one of:
      • VMOpcode.INVOKESTATIC - call a static method
      • VMOpcode.INVOKEVIRTUAL - call method declared in the class or super-class.
      • VMOpcode.INVOKEINTERFACE - call a method declared in an interface
                      static methods
      
                      Stack ...,value* => [numArgs number of values will be popped]
                            ...,return_value [void methods will not push a value]
      
                      non-static methods
      
                      Stack ...,ref,value* => [numArgs number of values will be popped]
                            ...,return_value [void methods will not push a value]
                      

      The type of the arguments to the methods must exactly match the declared types of the parameters to the methods. If a argument is of the incorrect type the caller must up cast it or down cast it.
      Parameters:
      type - type of method invocation
      declaringClass - Class or interface the method is declared in. If it is a non-static method call then if declaringClass is null, the declared type is taken to be the type of the reference that will be popped.
      methodName - name of the method
      returnType - class name or primitive type (including "void") of the return type of the method, can not be null.
      numArgs - number of arguments to the method (can be 0).
    • describeMethod

      Object describeMethod(short opcode, String declaringClass, String methodName, String returnType)
      Return an object that efficiently (to the implementation) describes a zero-argument method and can be used with the single argument callMethod(). Descriptions for the parameters to this method are the same as the five argument callMethod(). This allows the caller to cache frequently used methods. The returned object is only valid for use by this MethodBuilder.
      This call does not affect the Stack.
    • callMethod

      int callMethod(Object methodDescriptor)
      Call a method previously described by describeMethod().
                      static methods
      
                      Stack ...,value* => [numArgs number of values will be popped]
                            ...,return_value [void methods will not push a value]
      
                      non-static methods
      
                      Stack ...,ref,value* => [numArgs number of values will be popped]
                            ...,return_value [void methods will not push a value]
                      
    • callSuper

      void callSuper()
      Call super(). Caller must only add this to a constructor.
      
                      Stack ... =>
                            ... 
                      
    • getArrayElement

      void getArrayElement(int element)
      Pop an array refrence off the stack and push an element from that array.
                      Stack ...,array_ref =>
                            ...,value
                      
      Parameters:
      element - Offset into the array (zero based)
    • setArrayElement

      void setArrayElement(int element)
      Pop an array reference off the stack, store a value in the array at the passed in offset.
                      Stack ...,array_ref, value =>
                            ...
                      
      Parameters:
      element - Offset into the array (zero based)
    • swap

      void swap()
      Swap the top two values on the stack.
                      Stack ...,valueA,valueB =>
                            ...,valueB,valueA
                      
    • dup

      void dup()
      Duplicate the top value on the stack.
                      Stack ...,value =>
                            ...,value,value
                      
    • statementNumHitLimit

      boolean statementNumHitLimit(int noStatementsAdded)
      Tell if statement number in this method builder hits limit. This method builder keeps a counter of how many statements are added to it. Caller should call this function every time it tries to add a statement to this method builder (counter is increased by 1), then the function returns whether the accumulated statement number hits a limit. The reason of doing this is that Java compiler has a limit of 64K code size for each method. We might hit this limit if an extremely long insert statement is issued, for example (see beetle 4293). Counting statement number is an approximation without too much overhead.