How do I get the block's side which player is breaking?

[MrBendelScrolls]

I'm kinda new at modding and I don't understand some aspects.
I'm developing Hammers mod (tools that break blocks in a specified radius, usually 3x3). There's overrided onBlockStartBreak(ItemStack, BlockPos, EntityPlayer) method withing the ItemHammer class. How do I get the side of a block which player are pointing at while breaking?

[MrBendelScrolls]

I tried 2nd way and looks like it works fine. So, is this code okay in performance?
 

    @Override
    public boolean onBlockStartBreak(ItemStack itemstack, BlockPos pos, EntityPlayer player) {
        if (!player.isSneaking()) {
            RayTraceResult rayTrace = rayTrace(player.getEntityWorld(), player, false);
            switch (rayTrace.sideHit.getAxis()) {
                case X:
                    break;
                case Y:
                    break;
                case Z:
                    break;
            }
        }
        return super.onBlockStartBreak(itemstack, pos, player);
    }

And do I have to check the side to run it on the server only?