I want to read a binary file in JavaScript that would be gotten through XMLHttpRequest and be able to manipulate that data. From my researching I discovered this method of reading a binary file data into an array
var xhr = new XMLHttpRequest();
xhr.open('GET', '/binary_And_Ascii_File.obj', true);
xhr.responseType = 'arraybuffer';
xhr.onload = function(e) {
var uInt8Array = new Uint8Array(this.response);
};
How do I convert this binary data array to a human-readable-string?
I'm sure you will find this helpful: http://jsdo.it/tsmallfield/uint8array.
Click on javascript tab.
There will appear the code to convert the Uint8Array in a string. The author shows 2 method:
The first is about creating a view.
The second offsetting bytes.
EDIT: report the code for completeness
var buffer = new ArrayBuffer( res.length ), // res is this.response in your case
view = new Uint8Array( buffer ),
len = view.length,
fromCharCode = String.fromCharCode,
i, s, str;
/**
* 1) 8bitの配列に入れて上位ビットけずる
*/
str = "";
for ( i = len; i--; ) {
view[i] = res[i].charCodeAt(0);
}
for ( i = 0; i < len; ++i ) {
str += fromCharCode( view[i] );
}
/**
* 2) & 0xff で上位ビットけずる
*/
str = "";
for ( i = 0; i < len; ++i ) {
str += fromCharCode( res[i].charCodeAt(0) & 0xff );
}
function load_binary_resource(url) {
var byteArray = [];
var req = new XMLHttpRequest();
req.open('GET', url, false);
req.overrideMimeType('text\/plain; charset=x-user-defined');
req.send(null);
if (req.status != 200) return byteArray;
for (var i = 0; i < req.responseText.length; ++i) {
byteArray.push(req.responseText.charCodeAt(i) & 0xff)
}
return byteArray;
}
See https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Sending_and_Receiving_Binary_Data for more details
I have problem encrypting files with SJCL and javascript.
I have managed to encrypt text-files with using FileReader API and readAsBinaryString.
When it comes to encrypting pdf/png/.. then problem arrises probably due to encoding.
I found that I can use readAsArrayBuffer which suits this task perfectly, so I basically read file and create new typed array with new Uint8Array() but i dont know how exactly I am supposed to encrypt such a data.
Here's my code:
/** Convert from an array of bytes to a bitArray. */
function toBitArrayCodec(bytes) {
var out = [], i, tmp=0;
for (i=0; i<bytes.length; i++) {
tmp = tmp << 8 | bytes[i];
if ((i&3) === 3) {
out.push(tmp);
tmp = 0;
}
}
if (i&3) {
out.push(sjcl.bitArray.partial(8*(i&3), tmp));
}
return out;
}
/** Convert from a bitArray to an array of bytes. */
function fromBitArrayCodec(arr) {
var out = [], bl = sjcl.bitArray.bitLength(arr), i, tmp;
for (i=0; i<bl/8; i++) {
if ((i&3) === 0) {
tmp = arr[i/4];
}
out.push(tmp >>> 24);
tmp <<= 8;
}
return out;
}
var reader = new FileReader();
reader.readAsArrayBuffer(fileData); //filedata comes from function
reader.onload = function() {
var bytes = new Uint8Array(reader.result);
var bits = toBitArrayCodec(bytes);
var crypt = sjcl.encrypt("aaaaa", bits);
var decrypt = sjcl.decrypt("aaaaa", crypt);
var byteNumbers = fromBitArrayCodec(decrypt);
var byteArray = new Uint8Array(byteNumbers);
saveData(byteArray, 'png.png');
I am getting error on
Uncaught URIError: URI malformed sjcl.js:12sjcl.codec.utf8String.fromBits sjcl.js:12sjcl.json.decrypt sjcl.js:44reader.onload
I need to know how to encrypt uint8array or another alternative how to encrypt(pdf/png/..) files.
The plaintext in sjcl is expected to be utf8 encoded. Encrypting a manually built bitArray works, because the encryption is done on the bitArray and it doesn't have to be decoded. But at the end of the decryption is an encoding step which converts the recovered plaintext bitArray into a utf8string. This doesn't work, because it contains unprintable characters, because the source was probably binary.
The solution would be to encode it as Base64 before encrypting and convert it back after decrypting.
var bytes = new Uint8Array(reader.result);
var bits = toBitArrayCodec(bytes);
var base64bits = sjcl.codec.base64.fromBits(bits); // added
var crypt = sjcl.encrypt("aaaaa", base64bits);
var base64decrypt = sjcl.decrypt("aaaaa", crypt);
var decrypt = sjcl.codec.base64.toBits(base64decrypt); // added
var byteNumbers = fromBitArrayCodec(decrypt);
var byteArray = new Uint8Array(byteNumbers);
I want to add a string and some binaries like 0x00 inside my binary file which I loaded via ajax (to get it as binary)
This is my code until now:
var ajax = new XMLHttpRequest();
ajax.open("GET", "test.bin", true);
ajax.responseType = "arraybuffer";
ajax.onload = function () {
var byteArray = new Uint8Array(ajax.response);
// What can i do?
};
ajax.send();
Well, at last I could resolve it:
var str = 'Injected!!!';
var injAr = [0x21,0xFE,str.length];
for (var i = 0; i < str.length; i++) { injAr.push(str.charCodeAt(i));}
injAr.push(0x00,0x3B);
var ajax = new XMLHttpRequest();
ajax.open("GET", "test.gif", true);
ajax.responseType = "arraybuffer";
ajax.onload = function () {
var bAr = new Uint8Array(ajax.response), len = bAr.length - 1;
window.newBAr = new Uint8Array(len + injAr.length);
for (var i = 0; i < len; i++) { newBAr[i] = bAr[i];}
for (var i = 0; i < injAr.length; i++) { newBAr[len + i] = injAr[i];}
}
ajax.send();
Well, this was intended to add comments blocks to a gif correctly, but it can be use also with jpgs, pngs, for example to modify or add exif metadata
You will need to have the reqponse in a format that the javascript will be able to pull out the bytes that are the string and seperate the bytes that are part of the binary. You can do this by positioning the string at the beginning or end with a distinctive byte flag to signify the boundary. I would put the string at the beginning with the flag at the end of it to signify the beginning of the binary since I am unsure of the binary file.
Once you have it seperated, you will need to convert the bytes to numbers and then convert the numbers to characters. Here is a question that goes over how to convert binary to characters.
I need an efficient (read native) way to convert an ArrayBuffer to a base64 string which needs to be used on a multipart post.
function _arrayBufferToBase64( buffer ) {
var binary = '';
var bytes = new Uint8Array( buffer );
var len = bytes.byteLength;
for (var i = 0; i < len; i++) {
binary += String.fromCharCode( bytes[ i ] );
}
return window.btoa( binary );
}
but, non-native implementations are faster e.g. https://gist.github.com/958841
see http://jsperf.com/encoding-xhr-image-data/6
Updated benchmarks: https://jsben.ch/wnaZC
This works fine for me:
var base64String = btoa(String.fromCharCode.apply(null, new Uint8Array(arrayBuffer)));
In ES6, the syntax is a little simpler:
const base64String = btoa(String.fromCharCode(...new Uint8Array(arrayBuffer)));
As pointed out in the comments, this method may result in a runtime error in some browsers when the ArrayBuffer is large. The exact size limit is implementation dependent in any case.
For those who like it short, here's an other one using Array.reduce which will not cause stack overflow:
var base64 = btoa(
new Uint8Array(arrayBuffer)
.reduce((data, byte) => data + String.fromCharCode(byte), '')
);
There is another asynchronous way use Blob and FileReader.
I didn't test the performance. But it is a different way of thinking.
function arrayBufferToBase64( buffer, callback ) {
var blob = new Blob([buffer],{type:'application/octet-binary'});
var reader = new FileReader();
reader.onload = function(evt){
var dataurl = evt.target.result;
callback(dataurl.substr(dataurl.indexOf(',')+1));
};
reader.readAsDataURL(blob);
}
//example:
var buf = new Uint8Array([11,22,33]);
arrayBufferToBase64(buf, console.log.bind(console)); //"CxYh"
const blob = new Blob([array]);
const reader = new FileReader();
reader.onload = (event) => {
const dataUrl = event.target.result;
const [_, base64] = dataUrl.split(',');
// do something with base64
};
reader.readAsDataURL(blob);
Or as a promisified utility:
async function encode(array) {
return new Promise((resolve) => {
const blob = new Blob([array]);
const reader = new FileReader();
reader.onload = (event) => {
const dataUrl = event.target.result;
const [_, base64] = dataUrl.split(',');
resolve(base64);
};
reader.readAsDataURL(blob);
});
}
const encoded = await encode(typedArray);
The OP did not specify the Running Enviroment but if you are using Node.JS there is a very simple way to do such thing.
Accordig with the official Node.JS docs
https://nodejs.org/api/buffer.html#buffer_buffers_and_character_encodings
// This step is only necessary if you don't already have a Buffer Object
const buffer = Buffer.from(yourArrayBuffer);
const base64String = buffer.toString('base64');
Also, If you are running under Angular for example, the Buffer Class will also be made available in a Browser Environment.
My recommendation for this is to NOT use native btoa strategies—as they don't correctly encode all ArrayBuffer's…
rewrite the DOMs atob() and btoa()
Since DOMStrings are 16-bit-encoded strings, in most browsers calling window.btoa on a Unicode string will cause a Character Out Of Range exception if a character exceeds the range of a 8-bit ASCII-encoded character.
While I have never encountered this exact error, I have found that many of the ArrayBuffer's I have tried to encode have encoded incorrectly.
I would either use MDN recommendation or gist.
https://github.com/beatgammit/base64-js
https://gist.github.com/jonleighton/958841
I used this and works for me.
function arrayBufferToBase64( buffer ) {
var binary = '';
var bytes = new Uint8Array( buffer );
var len = bytes.byteLength;
for (var i = 0; i < len; i++) {
binary += String.fromCharCode( bytes[ i ] );
}
return window.btoa( binary );
}
function base64ToArrayBuffer(base64) {
var binary_string = window.atob(base64);
var len = binary_string.length;
var bytes = new Uint8Array( len );
for (var i = 0; i < len; i++) {
bytes[i] = binary_string.charCodeAt(i);
}
return bytes.buffer;
}
Below are 2 simple functions for converting Uint8Array to Base64 String and back again
arrayToBase64String(a) {
return btoa(String.fromCharCode(...a));
}
base64StringToArray(s) {
let asciiString = atob(s);
return new Uint8Array([...asciiString].map(char => char.charCodeAt(0)));
}
If you're okay with adding a library, base64-arraybuffer:
yarn add base64-arraybuffer
then:
encode(buffer) - Encodes ArrayBuffer into base64 string
decode(str) - Decodes base64 string to ArrayBuffer
This worked for me:
Buffer.from(myArrayBuffer).toString("base64");
ABtoB64(ab) {
return new Promise(res => {
const fr = new FileReader();
fr.onload = ({target: {result: s}}) => res(s.slice(s.indexOf(';base64,') + 8));
fr.readAsDataURL(new Blob([ab]));
});
}
asynchronous method using file reader.
You can derive a normal array from the ArrayBuffer by using Array.prototype.slice.
Use a function like Array.prototype.map to convert bytes in to characters and join them together to forma string.
function arrayBufferToBase64(ab){
var dView = new Uint8Array(ab); //Get a byte view
var arr = Array.prototype.slice.call(dView); //Create a normal array
var arr1 = arr.map(function(item){
return String.fromCharCode(item); //Convert
});
return window.btoa(arr1.join('')); //Form a string
}
This method is faster since there are no string concatenations running in it.
In the Browser suggested solutions with btoa seem fine.
But in Node.js btoa is deprecated
It is recommended to use buffer.toString(encoding)
like
const myString = buffer.toString("base64")
i use TextDecode api to convert it to normal text and then convert it to Base64
const uint = new Uint8Array([ 73, 32, 108, 111, 118, 101, 32, 121, 111, 117 ]).buffer
const decoder = new TextDecoder()
const decodedText = decoder.decode(uint)
const base64Code = btoa(decodedText)
Use uint8-to-b64 package to do encoding/decoding in browser and Node.js
By my side, using Chrome navigator, I had to use DataView() to read an arrayBuffer
function _arrayBufferToBase64( tabU8A ) {
var binary = '';
let lecteur_de_donnees = new DataView(tabU8A);
var len = lecteur_de_donnees.byteLength;
var chaine = '';
var pos1;
for (var i = 0; i < len; i++) {
binary += String.fromCharCode( lecteur_de_donnees.getUint8( i ) );
}
chaine = window.btoa( binary )
return chaine;}
function _arrayBufferToBase64(uarr) {
var strings = [], chunksize = 0xffff;
var len = uarr.length;
for (var i = 0; i * chunksize < len; i++){
strings.push(String.fromCharCode.apply(null, uarr.subarray(i * chunksize, (i + 1) * chunksize)));
}
return strings.join("");
}
This is better, if you use JSZip for unpack archive from string
i have this pseudo code and i would like to convert it into working code:
string constructSignature(string timestamp, string UID, string secretKey) {
baseString = timestamp + "_" + UID; // Construct a "base string" for signing
binaryBaseString = ConvertUTF8ToBytes(baseString); // Convert the base string into a binary array
binaryKey = ConvertFromBase64ToBytes(secretKey); // Convert secretKey from BASE64 to a binary array
binarySignature = hmacsha1(binaryKey, baseString); // Use the HMAC-SHA1 algorithm to calculate the signature
signature = ConvertToBase64(binarySignature); // Convert the signature to a BASE64
return signature;
}
any idea?
thanks
Some ideas:
Don't calculate BinaryBaseString, given that you never use it
Don't refer to UTF8 for no reason at all -- strings in JavaScript are Unicode, which is only distantly connected to UTF.
Don't put implementation details in your pseudocode -- especially ones you don't actually need (like assuming the secret key should be in "bytes", whatever that means, when in fact, the standard library takes and returns strings).
Don't write comments that just restate what the code is doing.
Which leaves us with:
var constructSignature = function(timestamp, UID, secretKey) {
return Crypto.HMAC(Crypto.SHA1, timestamp + "_" + UID, secretKey,
{ asString: true });
};
Here is a full implementation of your code:
let atob = function(a){
return new Buffer(a, 'base64').toString('binary');
}
function ConvertUTF8ToBytes(str) {
var utf8 = unescape(encodeURIComponent(str));
var arr = [];
for (var i = 0; i < utf8.length; i++) {
arr.push(utf8.charCodeAt(i));
}
return new Uint8Array(arr);
}
let ConvertFromBase64ToBytes = function (b64Data){
var byteCharacters = atob(b64Data);
var byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
return new Uint8Array(byteNumbers);
}
let constructSignature = function(timestamp, UID, secretKey) {
let baseString = timestamp + "_" + UID;
let binaryBaseString = ConvertUTF8ToBytes(baseString)
let binaryKey = ConvertFromBase64ToBytes(secretKey)
let binarySignature = Crypto.createHmac('sha1', binaryKey)
.update( binaryBaseString )
.digest('base64');
return binarySignature;
};