base

Documentation

Index

• func Branch(frame *chapter4_rtdt.Frame, offset int)
• func InitClass(thread *chapter4_rtdt.Thread, class *heap.Class)
• func InvokeMethod(invokerFrame *chapter4_rtdt.Frame, method *heap.Method)
• type BranchInstruction
  • func (self *BranchInstruction) FetchOperands(reader *BytecodeReader)
• type BytecodeReader
  • func (self *BytecodeReader) PC() int
  • func (self *BytecodeReader) ReadInt16() int16
  • func (self *BytecodeReader) ReadInt32() int32
  • func (self *BytecodeReader) ReadInt32s(len int32) []int32
  • func (self *BytecodeReader) ReadInt8() int8
  • func (self *BytecodeReader) ReadUInt16() uint16
  • func (self *BytecodeReader) ReadUInt8() uint8
  • func (self *BytecodeReader) Reset(code []byte, pc int)
  • func (self *BytecodeReader) SkipPadding()
• type Index16Instruction
  • func (self *Index16Instruction) FetchOperands(reader *BytecodeReader)
• type Index8Instruction
  • func (self *Index8Instruction) FetchOperands(reader *BytecodeReader)
• type Instruction
• type NoOperandsInstruction
  • func (self *NoOperandsInstruction) FetchOperands(reader *BytecodeReader)

Functions

func Branch

func Branch(frame *chapter4_rtdt.Frame, offset int)

*

跳转逻辑的基类

func InitClass

func InitClass(thread *chapter4_rtdt.Thread, class *heap.Class)

func InvokeMethod

func InvokeMethod(invokerFrame *chapter4_rtdt.Frame, method *heap.Method)

*

重点是参数传递：
1.确定方法的参数在局部变量表中占用多少位置，注意，这个数量不一定等于java代码中看到的参数个数，原因：
	1.long和double类型的参数要占用两个位置
	2.对于实例方法，java编译器会在参数列表的前面添加一个参数，这个参数的类型就是this引用
2.假设实际的参数占用 n 个位置，一次把这 n 个变量从调用者的操作数栈中弹出，放进调用方法的局部变量表中

Types

type BranchInstruction

type BranchInstruction struct {
	Offset int
}

*

表示跳转指令

func (*BranchInstruction) FetchOperands

func (self *BranchInstruction) FetchOperands(reader *BytecodeReader)

*

读取一个16字节的int

type BytecodeReader

type BytecodeReader struct {
	// contains filtered or unexported fields
}

func (*BytecodeReader) PC

func (self *BytecodeReader) PC() int

func (*BytecodeReader) ReadInt16

func (self *BytecodeReader) ReadInt16() int16

func (*BytecodeReader) ReadInt32

func (self *BytecodeReader) ReadInt32() int32

func (*BytecodeReader) ReadInt32s

func (self *BytecodeReader) ReadInt32s(len int32) []int32

func (*BytecodeReader) ReadInt8

func (self *BytecodeReader) ReadInt8() int8

func (*BytecodeReader) ReadUInt16

func (self *BytecodeReader) ReadUInt16() uint16

func (*BytecodeReader) ReadUInt8

func (self *BytecodeReader) ReadUInt8() uint8

func (*BytecodeReader) Reset

func (self *BytecodeReader) Reset(code []byte, pc int)

*

为了避免每次解码指令都新创建一个BytecodeReader实例

func (*BytecodeReader) SkipPadding

func (self *BytecodeReader) SkipPadding()

type Index16Instruction

type Index16Instruction struct {
	Index uint
}

*

用于指令访问运行时常量池，Index8Instruction用于访问局部变量表
有一些指令需要访问运行时常量池，常量池索引由两个字节的操作数给出

func (*Index16Instruction) FetchOperands

func (self *Index16Instruction) FetchOperands(reader *BytecodeReader)

type Index8Instruction

type Index8Instruction struct {
	Index uint
}

*

存储和加载指令需要根据索引存取 -> 局部变量表
索引由单字节操作数给出
用Index表示局部变量表索引

func (*Index8Instruction) FetchOperands

func (self *Index8Instruction) FetchOperands(reader *BytecodeReader)

type Instruction

type Instruction interface {
	//从字节码中提取操作数
	FetchOperands(reader *BytecodeReader)
	//执行具体指令
	Execute(frame *chapter4_rtdt.Frame)
}

*

操作码后面可以跟零字节或多字节的操作数，操作数就相当于函数的参数

type NoOperandsInstruction

type NoOperandsInstruction struct {
}

*

没有操作数的指令，及没有参数的指令

func (*NoOperandsInstruction) FetchOperands

func (self *NoOperandsInstruction) FetchOperands(reader *BytecodeReader)

*

什么也不做，这是个没有操作数的指令