以太坊聯合創始人 Vitalik Buterin 在 2022/8/31 宣佈他將發布一本新書「Proof of Stake」，將包含實體版（可以從各大通路買到）與數位版（一本 PDF）。書中總結了他過去十年來的各種寫作精華。
如果透過 gitcoin 的數位通路進行捐款，將可以獲得數位簽名版加上一個 NFT 作為回饋。
該募資網站： https://proofofstake.gitcoin.co
如上圖，在捐款後所獲得的 NFT 會紀錄什麼時候鑄造的、捐款多少、與合約地址。
既然有了合約地址，因此接下來的幾日，我們將依序拆解這個合約，來講講捐款、鑄造等合約的內容。
請注意，如果是輔助函式，在本系列中不會特別花力氣講解每一行的邏輯，只會提及該合約被引入的主要目的。
ProofOfStake_Pages.sol我們直接展開 ProofOfStake_Pages 合約中引入的函式庫與介面，可以看到以下的結構(* 為本日說明的範圍)
ProofOfStake_Pages
|- Ownable.sol
| |- Context.sol
|- ReentrancyGuard.sol
|- ERC721Enumerable.sol
| |- ERC721.sol
| | |- IERC721.sol
| | |- IERC165.sol
| | |- IERC721Receiver.sol
| | |- IERC721Metadata.sol
| | |- Address.sol
| | |- Context.sol
| | |- Strings.sol
| | |- ERC165.sol
| |- IERC721Enumerable.sol
| | |- IERC721.sol
| | |- IERC165.sol
|- Strings.sol
|- Counters.sol
|- base64.sol*
|- Transforms.sol*
Transforms.solTransforms 是一個輔助合約，他提供以下幾個功能：
v, r, s 三個部分。pragma solidity >=0.8.0 <0.9.0;
//SPDX-License-Identifier: MIT
library Transforms {
function splitSignature(bytes memory sig)
internal
pure
returns (
uint8 v,
bytes32 r,
bytes32 s
)
{
require(sig.length == 65);
assembly {
// first 32 bytes, after the length prefix.
r := mload(add(sig, 32))
// second 32 bytes.
s := mload(add(sig, 64))
// final byte (first byte of the next 32 bytes).
v := byte(0, mload(add(sig, 96)))
}
return (v, r, s);
}
/*///////////////////////////////////////////////////////////////
TYPE LOGIC
//////////////////////////////////////////////////////////////*/
function toAsciiString(address x) internal pure returns (string memory) {
bytes memory s = new bytes(40);
for (uint256 i = 0; i < 20; i++) {
bytes1 b = bytes1(uint8(uint256(uint160(x)) / (2**(8 * (19 - i)))));
bytes1 hi = bytes1(uint8(b) / 16);
bytes1 lo = bytes1(uint8(b) - 16 * uint8(hi));
s[2 * i] = char(hi);
s[2 * i + 1] = char(lo);
}
return string(s);
}
function char(bytes1 b) internal pure returns (bytes1 c) {
if (uint8(b) < 10) return bytes1(uint8(b) + 0x30);
else return bytes1(uint8(b) + 0x57);
}
}
base64.sol關於 base64 格式的細節，請參考維基百科
提供對 base64 格式的編碼與解碼函式：
encode：將一段資料（bytes 格式）編碼成一串 base64 格式的字串（string）decode：將 base64 格式的字串（string）解碼成原始資料（bytes）// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0;
/// @title Base64
/// @author Brecht Devos - <brecht@loopring.org>
/// @notice Provides functions for encoding/decoding base64
library Base64 {
string internal constant TABLE_ENCODE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
bytes internal constant TABLE_DECODE = hex"0000000000000000000000000000000000000000000000000000000000000000"
hex"00000000000000000000003e0000003f3435363738393a3b3c3d000000000000"
hex"00000102030405060708090a0b0c0d0e0f101112131415161718190000000000"
hex"001a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132330000000000";
function encode(bytes memory data) internal pure returns (string memory) {
if (data.length == 0) return '';
// load the table into memory
string memory table = TABLE_ENCODE;
// multiply by 4/3 rounded up
uint256 encodedLen = 4 * ((data.length + 2) / 3);
// add some extra buffer at the end required for the writing
string memory result = new string(encodedLen + 32);
assembly {
// set the actual output length
mstore(result, encodedLen)
// prepare the lookup table
let tablePtr := add(table, 1)
// input ptr
let dataPtr := data
let endPtr := add(dataPtr, mload(data))
// result ptr, jump over length
let resultPtr := add(result, 32)
// run over the input, 3 bytes at a time
for {} lt(dataPtr, endPtr) {}
{
// read 3 bytes
dataPtr := add(dataPtr, 3)
let input := mload(dataPtr)
// write 4 characters
mstore8(resultPtr, mload(add(tablePtr, and(shr(18, input), 0x3F))))
resultPtr := add(resultPtr, 1)
mstore8(resultPtr, mload(add(tablePtr, and(shr(12, input), 0x3F))))
resultPtr := add(resultPtr, 1)
mstore8(resultPtr, mload(add(tablePtr, and(shr( 6, input), 0x3F))))
resultPtr := add(resultPtr, 1)
mstore8(resultPtr, mload(add(tablePtr, and( input, 0x3F))))
resultPtr := add(resultPtr, 1)
}
// padding with '='
switch mod(mload(data), 3)
case 1 { mstore(sub(resultPtr, 2), shl(240, 0x3d3d)) }
case 2 { mstore(sub(resultPtr, 1), shl(248, 0x3d)) }
}
return result;
}
function decode(string memory _data) internal pure returns (bytes memory) {
bytes memory data = bytes(_data);
if (data.length == 0) return new bytes(0);
require(data.length % 4 == 0, "invalid base64 decoder input");
// load the table into memory
bytes memory table = TABLE_DECODE;
// every 4 characters represent 3 bytes
uint256 decodedLen = (data.length / 4) * 3;
// add some extra buffer at the end required for the writing
bytes memory result = new bytes(decodedLen + 32);
assembly {
// padding with '='
let lastBytes := mload(add(data, mload(data)))
if eq(and(lastBytes, 0xFF), 0x3d) {
decodedLen := sub(decodedLen, 1)
if eq(and(lastBytes, 0xFFFF), 0x3d3d) {
decodedLen := sub(decodedLen, 1)
}
}
// set the actual output length
mstore(result, decodedLen)
// prepare the lookup table
let tablePtr := add(table, 1)
// input ptr
let dataPtr := data
let endPtr := add(dataPtr, mload(data))
// result ptr, jump over length
let resultPtr := add(result, 32)
// run over the input, 4 characters at a time
for {} lt(dataPtr, endPtr) {}
{
// read 4 characters
dataPtr := add(dataPtr, 4)
let input := mload(dataPtr)
// write 3 bytes
let output := add(
add(
shl(18, and(mload(add(tablePtr, and(shr(24, input), 0xFF))), 0xFF)),
shl(12, and(mload(add(tablePtr, and(shr(16, input), 0xFF))), 0xFF))),
add(
shl( 6, and(mload(add(tablePtr, and(shr( 8, input), 0xFF))), 0xFF)),
and(mload(add(tablePtr, and( input , 0xFF))), 0xFF)
)
)
mstore(resultPtr, shl(232, output))
resultPtr := add(resultPtr, 3)
}
}
return result;
}
}
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