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pragma solidity ^0.4.18;
import "./KittyAccessControl.sol";
/// @title Base contract for CryptoKitties. Holds all common structs, events and base variables.
/// @author Axiom Zen (
/// @dev See the KittyCore contract documentation to understand how the various contract facets are arranged.
contract KittyBase is KittyAccessControl {
/*** EVENTS ***/
/// @dev The Birth event is fired whenever a new kitten comes into existence. This obviously
/// includes any time a cat is created through the giveBirth method, but it is also called
/// when a new gen0 cat is created.
event Birth(address indexed owner, uint256 kittyId, uint256 matronId, uint256 sireId, uint256 genes);
/// @dev Transfer event as defined in current draft of ERC721. Emitted every time a kitten
/// ownership is assigned, including births.
event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
/*** DATA TYPES ***/
/// @dev The main Kitty struct. Every cat in CryptoKitties is represented by a copy
/// of this structure, so great care was taken to ensure that it fits neatly into
/// exactly two 256-bit words. Note that the order of the members in this structure
/// is important because of the byte-packing rules used by Ethereum.
/// Ref:
struct Kitty {
// The Kitty's genetic code is packed into these 256-bits, the format is
// sooper-sekret! A cat's genes never change.
uint256 genes;
// The timestamp from the block when this cat came into existence.
uint64 birthTime;
// The minimum timestamp after which this cat can engage in breeding
// activities again. This same timestamp is used for the pregnancy
// timer (for matrons) as well as the siring cooldown.
uint64 cooldownEndTime;
// The ID of the parents of this kitty, set to 0 for gen0 cats.
// Note that using 32-bit unsigned integers limits us to a "mere"
// 4 billion cats. This number might seem small until you realize
// that Ethereum currently has a limit of about 500 million
// transactions per year! So, this definitely won't be a problem
// for several years (even as Ethereum learns to scale).
uint32 matronId;
uint32 sireId;
// Set to the ID of the sire cat for matrons that are pregnant,
// zero otherwise. A non-zero value here is how we know a cat
// is pregnant. Used to retrieve the genetic material for the new
// kitten when the birth transpires.
uint32 siringWithId;
// Set to the index in the cooldown array (see below) that represents
// the current cooldown duration for this Kitty. This starts at zero
// for gen0 cats, and is initialized to floor(generation/2) for others.
// Incremented by one for each successful breeding action, regardless
// of whether this cat is acting as matron or sire.
uint16 cooldownIndex;
// The "generation number" of this cat. Cats minted by the CK contract
// for sale are called "gen0" and have a generation number of 0. The
// generation number of all other cats is the larger of the two generation
// numbers of their parents, plus one.
// (i.e. max(matron.generation, sire.generation) + 1)
uint16 generation;
/*** CONSTANTS ***/
/// @dev A lookup table indicating the cooldown duration after any successful
/// breeding action, called "pregnancy time" for matrons and "siring cooldown"
/// for sires. Designed such that the cooldown roughly doubles each time a cat
/// is bred, encouraging owners not to just keep breeding the same cat over
/// and over again. Caps out at one week (a cat can breed an unbounded number
/// of times, and the maximum cooldown is always seven days).
uint32[14] public cooldowns = [
uint32(1 minutes),
uint32(2 minutes),
uint32(5 minutes),
uint32(10 minutes),
uint32(30 minutes),
uint32(1 hours),
uint32(2 hours),
uint32(4 hours),
uint32(8 hours),
uint32(16 hours),
uint32(1 days),
uint32(2 days),
uint32(4 days),
uint32(7 days)
/*** STORAGE ***/
/// @dev An array containing the Kitty struct for all Kitties in existence. The ID
/// of each cat is actually an index into this array. Note that ID 0 is a negacat,
/// the unKitty, the mythical beast that is the parent of all gen0 cats. A bizarre
/// creature that is both matron and sire... to itself! Has an invalid genetic code.
/// In other words, cat ID 0 is invalid... ;-)
Kitty[] kitties;
/// @dev A mapping from cat IDs to the address that owns them. All cats have
/// some valid owner address, even gen0 cats are created with a non-zero owner.
mapping (uint256 => address) public kittyIndexToOwner;
// @dev A mapping from owner address to count of tokens that address owns.
// Used internally inside balanceOf() to resolve ownership count.
mapping (address => uint256) ownershipTokenCount;
/// @dev A mapping from KittyIDs to an address that has been approved to call
/// transferFrom(). Each Kitty can only have one approved address for transfer
/// at any time. A zero value means no approval is outstanding.
mapping (uint256 => address) public kittyIndexToApproved;
/// @dev A mapping from KittyIDs to an address that has been approved to use
/// this Kitty for siring via breedWith(). Each Kitty can only have one approved
/// address for siring at any time. A zero value means no approval is outstanding.
mapping (uint256 => address) public sireAllowedToAddress;
/// @dev Assigns ownership of a specific Kitty to an address.
function _transfer(address _from, address _to, uint256 _tokenId) internal {
// since the number of kittens is capped to 2^32
// there is no way to overflow this
// transfer ownership
kittyIndexToOwner[_tokenId] = _to;
// When creating new kittens _from is 0x0, but we can't account that address.
if (_from != address(0)) {
// once the kitten is transferred also clear sire allowances
delete sireAllowedToAddress[_tokenId];
// clear any previously approved ownership exchange
delete kittyIndexToApproved[_tokenId];
// Emit the transfer event.
Transfer(_from, _to, _tokenId);
/// @dev An internal method that creates a new kitty and stores it. This
/// method doesn't do any checking and should only be called when the
/// input data is known to be valid. Will generate both a Birth event
/// and a Transfer event.
/// @param _matronId The kitty ID of the matron of this cat (zero for gen0)
/// @param _sireId The kitty ID of the sire of this cat (zero for gen0)
/// @param _generation The generation number of this cat, must be computed by caller.
/// @param _genes The kitty's genetic code.
/// @param _owner The inital owner of this cat, must be non-zero (except for the unKitty, ID 0)
function _createKitty(
uint256 _matronId,
uint256 _sireId,
uint256 _generation,
uint256 _genes,
address _owner
returns (uint)
// These requires are not strictly necessary, our calling code should make
// sure that these conditions are never broken. However! _createKitty() is already
// an expensive call (for storage), and it doesn't hurt to be especially careful
// to ensure our data structures are always valid.
require(_matronId <= 4294967295);
require(_sireId <= 4294967295);
require(_generation <= 65535);
Kitty memory _kitty = Kitty({
genes: _genes,
birthTime: uint64(now),
cooldownEndTime: 0,
matronId: uint32(_matronId),
sireId: uint32(_sireId),
siringWithId: 0,
cooldownIndex: 0,
generation: uint16(_generation)
uint256 newKittenId = kitties.push(_kitty) - 1;
// It's probably never going to happen, 4 billion cats is A LOT, but
// let's just be 100% sure we never let this happen.
require(newKittenId <= 4294967295);
// emit the birth event
// This will assign ownership, and also emit the Transfer event as
// per ERC721 draft
_transfer(0, _owner, newKittenId);
return newKittenId;
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