ForgePatch/common/net/minecraftforge/liquids/ILiquidTank.java

package net.minecraftforge.liquids;

/**
 * A tank is the unit of interaction with liquid inventories.
 *
 * @author cpw
 */
public interface ILiquidTank {

    /**
     * @return LiquidStack representing the liquid contained in the tank, null if empty.
     */
    LiquidStack getLiquid();

    /**
     * @return capacity of this tank
     */
    int getCapacity();

    /**
     *
     * @param resource
     * @param doFill
     * @return Amount of liquid used for filling.
     */
    int fill(LiquidStack resource, boolean doFill);
    /**
     *
     * @param maxDrain
     * @param doDrain
     * @return Null if nothing was drained, otherwise a LiquidStack containing the drained.
     */
    LiquidStack drain(int maxDrain, boolean doDrain);

    /**
     * Positive values indicate a positive liquid pressure (liquid wants to leave this tank)
     * Negative values indicate a negative liquid pressure (liquid wants to fill this tank)
     * Zero indicates no pressure
     *
     * @return a number indicating tank pressure
     */
    public int getTankPressure();

}