Both. Your body will need energy to burn to make your workout as effective as possible, a snack like a banana and a cup of yogurt, or a sandwich with wheat bread and peanut butter would be great. If you’re body has no fuel, it will take from stored protein or fat. What usually happens is your body ends up cannibalizing on it’s own muscle for energy. After your workout you’ll want to give the body protein for muscle recovery, if you’re planning on going right to bed soon after, you may not need as many carbohydrates.
The ADA recommends that the general population have a snack about an hour before a workout. The snack should be relatively high in carbohydrates and moderate in protein while being low in fat. Also, keep in mind the Glycemic Index of the food. A banana is often a safe bet for many people because it has a GI of 70, which is high. Foods with higer GI scores will cause a faster rise in blood glucose, which is good for a workout.
You might want to look into casein protein. It’s a slow-absorbing, complete protein that is generally good for supplying your body with continuous amounts of quality protein over a period of about 8 hours, or while you sleep. Do some research on this and as always, consult a registered dietitian before you make any big changes in your diet!
I hope this was helpful!