Cross-browser binary data processing in javascript

Question

We wish to use javascript to manipulate binary data. While this can be done with ArrayBuffer, ArrayBuffer is not supported in older browsers, how would you recommend doing this?

Answer 1

One option you have is to store binary data in an Array and write functions to access in the same way as ArrayBuffers and UintXArrays. This might also be a shim to DataView.

This should not be a too hard task and still performs reasonably.

An example:

function getInt8(byteOffset)
{
    return (byteArray[byteOffset] << 24) >> 24; // moves sign bit to bit 32
}

function getUint8(byteOffset)
{
    return byteArray[byteOffset];
}

function getUint16(byteOffset)
{
    return byteArray[byteOffset] | byteArray[byteOffset + 1] << 8;
}

function setUint8(byteOffset, value)
{
    byteArray[byteOffset] = value & 0xff; // make sure to mask values
}

// etc...

This requires some bitwise magic, but you should be able to figure it out with some google.

There is also a lot of content on how IE handles binary data (for instance this extensive thread about XMLHttpRequests).