How to get binary string from ArrayBuffer?

Question

What is the way to obtain binary string from ArrayBuffer in JavaScript?

I don't want to encode the bytes, just get the binary representation as String.

Thanks in advance!

Answer 1

The following code will consistently convert an ArrayBuffer to a String and back again without losing or adding any additional bytes.

function ArrayBufferToString(buffer) {
    return BinaryToString(String.fromCharCode.apply(null, Array.prototype.slice.apply(new Uint8Array(buffer))));
}

function StringToArrayBuffer(string) {
    return StringToUint8Array(string).buffer;
}

function BinaryToString(binary) {
    var error;

    try {
        return decodeURIComponent(escape(binary));
    } catch (_error) {
        error = _error;
        if (error instanceof URIError) {
            return binary;
        } else {
            throw error;
        }
    }
}

function StringToBinary(string) {
    var chars, code, i, isUCS2, len, _i;

    len = string.length;
    chars = [];
    isUCS2 = false;
    for (i = _i = 0; 0 <= len ? _i < len : _i > len; i = 0 <= len ? ++_i : --_i) {
        code = String.prototype.charCodeAt.call(string, i);
        if (code > 255) {
            isUCS2 = true;
            chars = null;
            break;
        } else {
            chars.push(code);
        }
    }
    if (isUCS2 === true) {
        return unescape(encodeURIComponent(string));
    } else {
        return String.fromCharCode.apply(null, Array.prototype.slice.apply(chars));
    }
}

function StringToUint8Array(string) {
    var binary, binLen, buffer, chars, i, _i;
    binary = StringToBinary(string);
    binLen = binary.length;
    buffer = new ArrayBuffer(binLen);
    chars  = new Uint8Array(buffer);
    for (i = _i = 0; 0 <= binLen ? _i < binLen : _i > binLen; i = 0 <= binLen ? ++_i : --_i) {
        chars[i] = String.prototype.charCodeAt.call(binary, i);
    }
    return chars;
}

I tested it by round-tripping the following values in this jsfiddle: http://jsfiddle.net/potatosalad/jrdLV/

(String) "abc" -> (ArrayBuffer) -> (String) "abc"
(String) "aΩc" -> (ArrayBuffer) -> (String) "aΩc"
(Uint8Array) [0,1,255] -> (ArrayBuffer) -> (String) -> (Uint8Array) [0,1,255]
(Uint16Array) [0,1,256,65535] -> (ArrayBuffer) -> (String) -> (Uint16Array) [0,1,256,65535]
(Uint32Array) [0,1,256,65536,4294967295] -> (ArrayBuffer) -> (String) -> (Uint32Array) [0,1,256,65536,4294967295]