Eating at night before fast

I get up for work at 5 in the morning. I noticed that on the fast day of the Tenth of Teves (which is a daytime-only fast) the time of “alos ha-shahar” is after 5. Does that mean that I am allowed to eat and drink before “alos ha-shahar”? (“Alos ha-shahar” is the time of the appearance of the first rays of sunlight over the horizon.)  

Dear …!

Normally, because people don’t usually wake up in the middle of the night to eat and drink, someone who goes to sleep on the eve of the fast and then wakes up before alos ha-shahar is not allowed to eat. The reason is that his going to sleep is tantamount to his accepting the fast upon himself.

However, someone who is used to waking up in the middle of the night to eat or drink, can eat until the time of alos ha-shahar.

Therefore, if you are used to eating or drinking when you wake up for work, you are allowed to eat and drink till the time of alos ha-shahar. And if you are not used to it, it’s forbidden for you to eat.

However, if at night before going to sleep you make an explicit stipulation that you do not intend to begin the fast by going to sleep, but only at alos ha-shachar, then you will be allowed to eat and drink when you wake up early in the morning before the fast.

Shulchan Oruch, section Orach Chaim, chapter 564