Question

所以我将这个代码用于我的模拟器，将字节转换为十六进制

byteToHex(opcode) {
        var tempCode = (opcode).toString(16).toUpperCase()
        var addln = 4 - tempCode.length
        var pad =""
        for(var i = 0; i< addln; i++) {
            pad = pad + "0"
        }
        var newCode = "0x"+ pad + tempCode
        return newCode;
}

我有这个代码执行按位操作来获取操作码然后转换它以供使用。

this.opcode = (this.memory[this.pc] << 8) | this.memory[this.pc + 1]
    console.log(this.memory)
    console.log("before conversion", this.opcode)
    this.opcode = this.byteToHex(this.opcode)
    console.log(this.opcode)
    //this just returns the first 'letter' of the opcode
    switch (this.opcode & 0xF000)...

这是控制台输出

Array [ 240, 144, 144, 144, 240, 32, 96, 32, 32, 112, 70 more… ] 
before conversion 0
0x0000

这意味着我错误地获取了操作码，但我不知道如何修复它。为了更好地了解项目：Github

Answer 1

这是一些按预期运行的代码。调试你的（不完整的）代码有点困难。由于StackOverflow是关于具体的问题和答案，我甚至不打算玩你需要解决的猜测/侦探游戏...

240d = 0xF0

144d = 0x90

[240,144]被视为单个16位大端数字是0xF090（英特尔的东西是小端，即最不重要的字节首先出现）

window.addEventListener('load', onDocLoaded, false);

var memoryContents = [240, 144, 144, 144, 240, 32, 96, 32, 32, 112];

function getTwoLocationsBigEndian(indexOfFirst)
{
	var result = (memoryContents[indexOfFirst] << 8) | (memoryContents[indexOfFirst+1]);
	return result;
}

function getTwoLocationsLittleEndian(indexOfFirst)
{
	var result = (memoryContents[indexOfFirst+1] << 8) | (memoryContents[indexOfFirst]);
	return result;
}

function byteToHex(opcode)
{
	var tempCode = (opcode).toString(16).toUpperCase()
	var addln = 4 - tempCode.length
	var pad =""
	for(var i = 0; i< addln; i++)
	{
		pad = pad + "0"
	}
	var newCode = "0x"+ pad + tempCode
	return newCode;
}

function onDocLoaded(evt)
{
	console.log("Memory contents: " + memoryContents);
	
	var opcode = getTwoLocationsBigEndian(0);
	console.log("***** BIG endian *****");
	console.log("First 2 locs as a 16bit num (dec): " + opcode );
	console.log("First 2 locs as a 16bit num (hex): " + byteToHex(opcode) );

	opcode = getTwoLocationsLittleEndian(0);
	console.log("***** LITTLE endian *****");
	console.log("First 2 locs as a 16bit num (dec): " + opcode );
	console.log("First 2 locs as a 16bit num (hex): " + byteToHex(opcode) );
}

为什么我的按位操作在我的模拟器中返回0？

1 个答案: