See the SipHash home page for info.

You need to create a state object of class siphash.SipHash:

var sh = new siphash.SipHash();

Then you need to specify a key. This operation also resets the internal state, so you can use it to start a new authentication without creating new state:

sh.reset(key);

Next you feed it buffers of data you want authenticated. Note, that each next block of data adds to stream, not replaces it. If you feed it blocks that aren't multiples of 8 bytes, remainder of data will be stored inside and used with the begining of next block:

sh.update(buffer, 10 /* offset */, len - 10 /* length */);
sh.update(buffer, 10); // same as above
sh.update(buffer); // use th whole buffer

Finally you make the authentication tag:

var tag : haxe.Int64 = sh.complete();

Or if you just need to hash one buffer:

var sh = new siphash.SipHash(); // do this once

var result = sh.reset(key).fast(buffer, 10, 25); // do this for every buffer

This interface is slightly faster as it doesn't save intermediate state while reading the buffer.

public function reset(k : haxe.io.Int32Array, mode128 : Bool = false)

Resets internal state and initializes it with provided key. Allows more than one plaintext to be processed with a single SipHash object.

public function update(k : haxe.io.Bytes, pos : Int = 0, ?len : Int)

Updates internal state with provided buffer. If len is unspecified, uses k.length - pos bytes from buffer.

public function complete() : Int64

Completes the final transform and outputs authentication tag.

public function fast(buf : haxe.io.Bytes, pos : Int = 0, ? len : Int) : Int64

Does update and complete in one call. Faster, but supports only one buffer.