[JavaScript]使用ArrayBuffer和Blob编辑二进制流

Blob()构造方法返回一个新的Blob对象. 内容是包含参数array的二进制字节流.

语法

var aBlob = new Blob( array, options );

参数

• array is an Array of ArrayBuffer, ArrayBufferView, Blob, DOMString objects, or a mix of any of such objects, that will be put inside the Blob. DOMStrings are encoded as UTF-8.
• options is an optional BlobPropertyBag dictionary which may specify the following two attributes:
  • type, with a default value of "", that represents the MIME type of the content of the array that will be put in the blob.
  • endings, with a default value of "transparent", that specifies how strings containing the line ending character \n are to be written out. It is one of the two values: "native", meaning that line ending characters are changed to match host OS filesystem convention, or "transparent", meaning that endings are stored in the blob without change.

var buffer = new ArrayBuffer(2);
var int8View = new Int8Array(buffer);
int8View[0] = 170;
int8View[1] = 254;

var blob = new Blob([int8View, event.target.result]);

 此段代码创建了一个2字节的二进制数10101010和11111110，并且把它追加到了event.target.result字节流的头部

var buffer = new ArrayBuffer(8);
var uInt32 = new Uint32Array(buffer);
uInt32[0]  = 2356021;

console.log(uInt32[0]); // 2356021
console.log(uInt32.length); // 2
console.log(uInt32.BYTES_PER_ELEMENT); // 4

var view = new DataView(buffer,0,8);
console.log(view.getUint32(0,4));//2356021

此段代码创建了2个无符号32位整数buff（一个unsigned int需要4个字节空间，所以new ArrayBuffer(8)分配了8个字节，即，可容纳8/4=2个unsigned int类型的整数）；

在第1个数组放置2356021，当然你可以使用uInt32[1]放置第二个值，但是你只能放置2个值，毕竟它只分配了8/4=2个unsigned int类型的整数；

调用length可查看ArrayBuffer的长度，这里是2，调用BYTES_PER_ELEMENT可查看每个元素占用的字节数，这里是4；

运用DataView可以以一种方式去读取某段buff的值；

 查看更多的例子：

运用XHR异步请求接收二进制流