将javascript Integer转换为Byte数组并返回 [英] Converting javascript Integer to Byte array and back

问题描述

function intFromBytes( x ){
    var val = 0;
    for (var i = 0; i < x.length; ++i) {        
        val += x[i];        
        if (i < x.length-1) {
            val = val << 8;
        }
    }
    return val;
}

function getInt64Bytes( x ){
    var bytes = [];
    var i = 8;
    do {
    bytes[--i] = x & (255);
    x = x>>8;
    } while ( i )
    return bytes;
}

我试图将javascript编号转换为字节数组然后返回一个号码。但是，上述函数产生的输出数量非常大。

I am trying to convert a javascript number to a byte array and then back to a number. However the above functions produce incorrect output with a very large number.

var array = getInt64Bytes(23423423);    
var value = intFromBytes(array);

console.log(value); //Prints 23423423 - correct

var array = getInt64Bytes(45035996273704);  
var value = intFromBytes(array);

console.log(value); //Prints -1030792152 - incorrect

据我所知，javascript浮点数为53位所以它不应该'溢出？ alert（Math.pow（2,53））工作正常。

It is my understanding that javascript floats are 53 bits so it shouldn't be overflowing? alert(Math.pow(2,53)) works fine.

推荐答案

在JavaScript位移位（ >> ，<< ）始终在带符号的32位整数上执行。这会导致大量范围溢出。

In JavaScript bit shifts (>>, <<) are always performed on signed, 32-bits integers. This leads to range overflow for large numbers.

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