javascript 在javascript中将32位整数转换为4字节的数据
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Convert a 32bit integer into 4 bytes of data in javascript
提问by user1647017
I was asked to convert the integers to 32-bit binary numbers.
So is used integer.toString(2)and got the required value in 32-bit binary format of 0'sand 1's. But actually what I was asked to do is convert the integer into 4 bytes of data.
I am unable to get the output as suggested. I have used integer.toString(8), integer.toString(16). but of no use.
我被要求将整数转换为 32 位二进制数。so 被使用integer.toString(2)并以 0's 和 1's 的 32 位二进制格式得到所需的值。但实际上我被要求做的是将整数转换为 4 个字节的数据。我无法按照建议获得输出。我用过integer.toString(8)，integer.toString(16)。但没有用。
Example:
例子：
num=1065489844
num.toString(2) //Output: 111111100000100001010110110100
num.toString(8) //Output: 7740412664
Please let me know, where I am lacking.
请让我知道，我的不足之处。
回答by SEIAROTg
Now you can use ArrayBufferand DataView. They are native so the performance will be much better if you need to use it very often.
现在您可以使用ArrayBuffer和DataView。它们是原生的，因此如果您需要经常使用它，性能会好得多。
function toBytesInt32 (num) {
arr = new ArrayBuffer(4); // an Int32 takes 4 bytes
view = new DataView(arr);
view.setUint32(0, num, false); // byteOffset = 0; litteEndian = false
return arr;
}
equals to
等于
function toBytesInt32 (num) {
arr = new Uint8Array([
(num & 0xff000000) >> 24,
(num & 0x00ff0000) >> 16,
(num & 0x0000ff00) >> 8,
(num & 0x000000ff)
]);
return arr.buffer;
}
which use javascript bitwise operators to achieve that.
它使用 javascript 按位运算符来实现这一点。
回答by Matthew Cornelisse
SEIAROTg's answer does not output a string. I have theroughly tested with both positive and negative numbers and this code will give you a 4 byte string output representing the number in big endien format(2's compliment 0xFFFFFFFF = -1).
SEIAROTg 的答案不输出字符串。我已经对正数和负数进行了粗略的测试，这段代码会给你一个 4 字节的字符串输出，代表大端格式的数字（2 的恭维 0xFFFFFFFF = -1）。
var toBytesInt32=function(num) {
var ascii='';
for (let i=3;i>=0;i--) {
ascii+=String.fromCharCode((num>>(8*i))&255);
}
return ascii;
};
by the way if you want to go the other way around you can use
顺便说一句，如果你想反过来，你可以使用
var fromBytesInt32=function(numString) {
var result=0;
for (let i=3;i>=0;i--) {
result+=numString.charCodeAt(3-i)<<(8*i);
}
return result;
};
to convert a 4 byte string to an integer
将 4 字节字符串转换为整数
回答by Bechir
if you need a hex format output, here is the code.
如果您需要十六进制格式输出，这里是代码。
/* Convert value as 8-bit unsigned integer to 2 digit hexadecimal number. */
function hex8(val) {
val &= 0xFF;
var hex = val.toString(16).toUpperCase();
return ("00" + hex).slice(-2);
}
/* Convert value as 16-bit unsigned integer to 4 digit hexadecimal number. */
function hex16(val) {
val &= 0xFFFF;
var hex = val.toString(16).toUpperCase();
return ("0000" + hex).slice(-4);
}
/* Convert value as 32-bit unsigned integer to 8 digit hexadecimal number. */
function hex32(val) {
val &= 0xFFFFFFFF;
var hex = val.toString(16).toUpperCase();
return ("00000000" + hex).slice(-8);
}
var num = 1065489844;
console.log("0x" + hex32(num)); // will output 0x3F8215B4
