Uint8Array to ArrayBuffer

Question

So I have a ArrayBuffer which is of the file contents of a file which I read with the new HTML5 file reader as ArrayBuffer(), and I can convert the ArrayBuffer to Uint8Array by doing the following.

//ab = established and defined ArrayBuffer  var foobar = new Uint8Array([ab]);  //var reversed = reverseUint8Array(foobar);   //reversed should equal ab  

How do I reverse that last process back into ab?

Here is the kind of output I am getting after decryption: http://prntscr.com/b3zlxr

What kind of format is this, and how do I get it into blob?

Answer 1

I found a more simple method to get the ArrayBuffer of Uint8Array.

var arrayBuffer = foobar.buffer;  

just this! And it works for me!

Answer 2

With kuokongqingyun option, it will not always work, because the buffer may be bigger than the data view.

See this example:

let data = Uint8Array.from([1,2,3,4]) var foobar = data.subarray(0,2) var arrayBuffer = foobar.buffer;   console.log(new Uint8Array(arrayBuffer)) // will print [1,2,3,4] but we want [1,2] 

When using array.buffer it's important use byteOffset and byteLength to compute the actual data

let data = Uint8Array.from([1,2,3,4]) var foobar = data.subarray(0,2) var arrayBuffer = foobar.buffer.slice(foobar.byteOffset, foobar.byteLength + foobar.byteOffset);   console.log(new Uint8Array(arrayBuffer)) // OK it now prints [1,2] 

So here is the function you need:

function typedArrayToBuffer(array: Uint8Array): ArrayBuffer {     return array.buffer.slice(array.byteOffset, array.byteLength + array.byteOffset) }