Contract Source Code:
File 1 of 1 : PriceFeed
/// price-feed.sol
// Copyright (C) 2017 DappHub, LLC
// Licensed under the Apache License, Version 2.0 (the "License").
// You may not use this file except in compliance with the License.
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND (express or implied).
pragma solidity ^0.4.17;
contract DSAuthority {
function canCall(
address src, address dst, bytes4 sig
) public view returns (bool);
}
contract DSAuthEvents {
event LogSetAuthority (address indexed authority);
event LogSetOwner (address indexed owner);
}
contract DSAuth is DSAuthEvents {
DSAuthority public authority;
address public owner;
function DSAuth() public {
owner = msg.sender;
LogSetOwner(msg.sender);
}
function setOwner(address owner_)
public
auth
{
owner = owner_;
LogSetOwner(owner);
}
function setAuthority(DSAuthority authority_)
public
auth
{
authority = authority_;
LogSetAuthority(authority);
}
modifier auth {
require(isAuthorized(msg.sender, msg.sig));
_;
}
function isAuthorized(address src, bytes4 sig) internal view returns (bool) {
if (src == address(this)) {
return true;
} else if (src == owner) {
return true;
} else if (authority == DSAuthority(0)) {
return false;
} else {
return authority.canCall(src, this, sig);
}
}
}
contract DSNote {
event LogNote(
bytes4 indexed sig,
address indexed guy,
bytes32 indexed foo,
bytes32 indexed bar,
uint wad,
bytes fax
) anonymous;
modifier note {
bytes32 foo;
bytes32 bar;
assembly {
foo := calldataload(4)
bar := calldataload(36)
}
LogNote(msg.sig, msg.sender, foo, bar, msg.value, msg.data);
_;
}
}
contract DSMath {
function add(uint x, uint y) internal pure returns (uint z) {
require((z = x + y) >= x);
}
function sub(uint x, uint y) internal pure returns (uint z) {
require((z = x - y) <= x);
}
function mul(uint x, uint y) internal pure returns (uint z) {
require(y == 0 || (z = x * y) / y == x);
}
function min(uint x, uint y) internal pure returns (uint z) {
return x <= y ? x : y;
}
function max(uint x, uint y) internal pure returns (uint z) {
return x >= y ? x : y;
}
function imin(int x, int y) internal pure returns (int z) {
return x <= y ? x : y;
}
function imax(int x, int y) internal pure returns (int z) {
return x >= y ? x : y;
}
uint constant WAD = 10 ** 18;
uint constant RAY = 10 ** 27;
function wmul(uint x, uint y) internal pure returns (uint z) {
z = add(mul(x, y), WAD / 2) / WAD;
}
function rmul(uint x, uint y) internal pure returns (uint z) {
z = add(mul(x, y), RAY / 2) / RAY;
}
function wdiv(uint x, uint y) internal pure returns (uint z) {
z = add(mul(x, WAD), y / 2) / y;
}
function rdiv(uint x, uint y) internal pure returns (uint z) {
z = add(mul(x, RAY), y / 2) / y;
}
// This famous algorithm is called "exponentiation by squaring"
// and calculates x^n with x as fixed-point and n as regular unsigned.
//
// It's O(log n), instead of O(n) for naive repeated multiplication.
//
// These facts are why it works:
//
// If n is even, then x^n = (x^2)^(n/2).
// If n is odd, then x^n = x * x^(n-1),
// and applying the equation for even x gives
// x^n = x * (x^2)^((n-1) / 2).
//
// Also, EVM division is flooring and
// floor[(n-1) / 2] = floor[n / 2].
//
function rpow(uint x, uint n) internal pure returns (uint z) {
z = n % 2 != 0 ? x : RAY;
for (n /= 2; n != 0; n /= 2) {
x = rmul(x, x);
if (n % 2 != 0) {
z = rmul(z, x);
}
}
}
}
contract DSThing is DSAuth, DSNote, DSMath {
}
contract PriceFeed is DSThing {
uint128 val;
uint32 public zzz;
function peek() public view
returns (bytes32,bool)
{
return (bytes32(val), now < zzz);
}
function read() public view
returns (bytes32)
{
assert(now < zzz);
return bytes32(val);
}
function post(uint128 val_, uint32 zzz_, address med_) public note auth
{
val = val_;
zzz = zzz_;
bool ret = med_.call(bytes4(keccak256("poke()")));
ret;
}
function void() public note auth
{
zzz = 0;
}
}