Minecraft Forums

ID	Code name	In-game name	Description
1	moveSpeed	Speed		Movement speed increases.
2	moveSlowdown	Slowness	Movement speed decreases.
3	digSpeed	Haste		Mining speed increases.
4	digSlowDown	Mining Fatigue	Mining speed decreases.
5	damageBoost	Strength	Damage dealt increases.
6	heal		Instant Health	Instant health as the name implies.
7	harm		Instant Damage	Instant damage, also as the name implies.
8	jump		Jump Boost	Increases jump height, level I: 1.75 blocks,  level II: 2.5 blocks, level III: 3.25 blocks and you will take a bit of fall damage.
9	confusion	Nausea		Screen goes wavy, makes walking difficult.
10	regeneration	Regeneration	Regenerates health(used on Golden apples.)
11	resistance	Resistance	Reduces damage received(unconfirmed to work on all damage types.)
12	fireResistance	Fire Resistance	Fire immunity, you will still catch fire, you can also dive in lava (you can not drown in it either).
13	waterBreathing	Water Breathing	Infinite breath, bubbles still appear but will not decrease.
14	invisibility	Invisibility	Does not seem to do anything as of now, mobs still attack and no visual change(broken.)
15	blindness	Blindness	Similar to the bedrock fog, you only see black after a few blocks.
16	nightVision	Night Vision	Totally and utterly broken, as per jeb.
17	hunger		Hunger		Food bar decreases faster than normal.
18	weakness	Weakness	Reduces damage you deal to enemies.
19	poison		Poison		Ticking damage, used by spiders.

• There is 32,767 different physical potion objects possible, combos to create duplicates of the same potions number more in the billions.
• Nether Wart is special, specifically it calls method g.

//Starts here input and output is current metadata
        public static int g(int metadata)
        {
                if((metadata & 1) != 0)
                        metadata = e(metadata);
                return f(metadata);
        }
 
        public static int e(int metadata)
        {
                if((metadata & 1) == 0)
                        return metadata;
                int pos;
                for(pos = 14; (metadata & 1 << pos) == 0 && pos >= 0; pos--);
                if(pos < 2 || (metadata & 1 << pos - 1) != 0)
                        return metadata;
                if(pos >= 0)
                        metadata &= ~(1 << pos);
                metadata <<= 1;
                if(pos >= 0)
                {
                        metadata |= 1 << pos;
                        metadata |= 1 << pos - 1;
                }
                return metadata & 0x7fff;
        }
 
        public static int f(int metadata)
        {
                int pos;
                for(pos = 14; (metadata & 1 << pos) == 0 && pos >= 0; pos--);
                if(pos >= 0)
                        metadata &= ~(1 << pos);
                int outNumber = 0;
                for(int modifiedMetadata = metadata; modifiedMetadata != outNumber;)
                {
                        modifiedMetadata = metadata;
                        outNumber = 0;
                        for(int bit = 0; bit < 15; bit++)
                        {
                                boolean hasBitsNearby = bitSetModulo(metadata, bit);
                                if(hasBitsNearby)
                                {
                                        if(!bitSetModulo(metadata, bit + 1) && bitSetModulo(metadata, bit + 2))
                                                hasBitsNearby = false;
                                        else
                                        if(!bitSetModulo(metadata, bit - 1) && bitSetModulo(metadata, bit - 2))
                                                hasBitsNearby = false;
                                } else
                                {
                                        hasBitsNearby = bitSetModulo(metadata, bit - 1) && bitSetModulo(metadata, bit + 1);
                                }
                                if(hasBitsNearby)
                                        outNumber |= 1 << bit;
                        }
 
                        metadata = outNumber;
                }
 
                if(pos >= 0)
                        outNumber |= 1 << pos;
                return outNumber & 0x7fff;
        }
 
        private static boolean bitSetModulo(int number, int bit)
        {
                return (number & 1 << bit % 15) != 0;
        }
 
        private static boolean bitSet(int number, int bit)
        {
                return (number & 1 << bit) != 0;
        }
 
        private static int bitSetInt(int number, int bit)
        {
                return bitSet(number, bit) ? 1 : 0;
        }