在保留字节的同时在JavaScript中连接十六进制字节和字符串 [英] Concatenating hex bytes and strings in JavaScript while preserving bytes

问题描述

  var hexValue = 0x89; 
我想用JavaScript连接一个十六进制值和一个字符串。 
 var png =PNG; 
  

字符串PNG相当于 0x50 ， 0x4E 和 0x47 。

连接 hexValue 和 png 通过

  var concatHex = String.fromCharCode（0x89）+ String.fromCharCode（0x50）
 + String.fromCharCode（0x4E）+ String.fromCharCode（0x47）; 
  

...给出一个字节数为5的结果，因为第一个十六进制值需要控制字符：

  C2 89 50 4E 47 
  

我正在处理原始图像数据，其中包含 hexValue 和 png 以及需要连接它们而不包含这个控制字符。

1. 有没有办法修剪控制字符？


2. 给定我有一个字节数组，有没有更好的方法来连接它们和一个字符串，同时保留字节？
   

解决方案

好的，我正在调查，我发现在JavaScript中实现这个eficienly JavaScript类型的数组被使用。

https： //developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays

http://msdn.microsoft.com/en-us/library/br212485（v = vs.94） .aspx

这里我写了一个代码（未测试）来执行你想要的操作：

  var png =PNG; 
 var hexValue = 0x89; 
 var lenInBytes =（png.Length + 1）* 8; //留下一个额外的空间来连接hexValue 
 
 var buffer = new ArrayBuffer（lenInBytes）; //创建大块内存，其字节全部预初始化为0 
 var int8View = new Int8Array（buffer）; //把这个内存当作int8 
 
来处理（int i = 0; i< png.Length; i ++）
 int8View [i] = png [i] //这里转换png [i]到字节
 
 //此时，我们将字符串png作为字节数组
 
 int8View [png.Length] = hexValue //在这里执行并置
  

好希望它有帮助。

I would like to concatenate a hex value and a string using JavaScript.

var hexValue = 0x89;
var png = "PNG";

The string "PNG" is equivalent to the concatenation of 0x50, 0x4E, and 0x47.

Concatenating hexValue and png via

var concatHex = String.fromCharCode(0x89) + String.fromCharCode(0x50) 
              + String.fromCharCode(0x4E) + String.fromCharCode(0x47);

...give a result with a byte count of 5 because of the first hex value needing a control character:

C2 89 50 4E 47

I am working with raw image data where I have hexValue and png and need to concatenate them without this control character being included.

1. Is there a way to trim off the control character?
2. Given I have an array of bytes, is there a better way to concatenate them and a string while preserving the bytes?

解决方案

Well i was investigating and i found that in javascript to achieve this eficienly JavaScript typed arrays is used.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays

http://msdn.microsoft.com/en-us/library/br212485(v=vs.94).aspx

Here i wrote a code (not tested) to perform what you want:

var png = "PNG";
var hexValue = 0x89;
var lenInBytes = (png.Length + 1) * 8; //left an extra space to concat hexValue

var buffer = new ArrayBuffer(lenInBytes); //create chunk of memory whose bytes are all pre-initialized to 0
var int8View = new Int8Array(buffer); //treat this memory like int8

for(int i = 0; i < png.Length ; i++)
    int8View[i] = png[i]  //here convert the png[i] to bytes

//at this point we have the string png as array of bytes

    int8View[png.Length] = hexValue //here the concatenation is performed

Well hope it helps.

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