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Add Base64Url encoding (#4822)

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Co-authored-by: Ernesto García <ernestognw@gmail.com>
This commit is contained in:
Hadrien Croubois
2024-01-16 23:12:50 +01:00
committed by GitHub
parent 281ab15886
commit 692dbc560f
6 changed files with 133 additions and 22 deletions
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53
contracts/utils/Base64.sol
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@ -9,29 +9,48 @@ pragma solidity ^0.8.20;
library Base64 {
/**
* @dev Base64 Encoding/Decoding Table
* See sections 4 and 5 of https://datatracker.ietf.org/doc/html/rfc4648
*/
string internal constant _TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
string internal constant _TABLE_URL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
/**
* @dev Converts a `bytes` to its Bytes64 `string` representation.
*/
function encode(bytes memory data) internal pure returns (string memory) {
return _encode(data, _TABLE, true);
}
/**
* @dev Converts a `bytes` to its Bytes64Url `string` representation.
*/
function encodeURL(bytes memory data) internal pure returns (string memory) {
return _encode(data, _TABLE_URL, false);
}
/**
* @dev Internal table-agnostic conversion
*/
function _encode(bytes memory data, string memory table, bool withPadding) private pure returns (string memory) {
/**
* Inspired by Brecht Devos (Brechtpd) implementation - MIT licence
* https://github.com/Brechtpd/base64/blob/e78d9fd951e7b0977ddca77d92dc85183770daf4/base64.sol
*/
if (data.length == 0) return "";
// Loads the table into memory
string memory table = _TABLE;
// Encoding takes 3 bytes chunks of binary data from `bytes` data parameter
// and split into 4 numbers of 6 bits.
// The final Base64 length should be `bytes` data length multiplied by 4/3 rounded up
// If padding is enabled, the final length should be `bytes` data length divided by 3 rounded up and then
// multiplied by 4 so that it leaves room for padding the last chunk
// - `data.length + 2` -> Round up
// - `/ 3` -> Number of 3-bytes chunks
// - `4 *` -> 4 characters for each chunk
string memory result = new string(4 * ((data.length + 2) / 3));
// If padding is disabled, the final length should be `bytes` data length multiplied by 4/3 rounded up as
// opposed to when padding is required to fill the last chunk.
// - `4 *` -> 4 characters for each chunk
// - `data.length + 2` -> Round up
// - `/ 3` -> Number of 3-bytes chunks
uint256 resultLength = withPadding ? 4 * ((data.length + 2) / 3) : (4 * data.length + 2) / 3;
string memory result = new string(resultLength);
/// @solidity memory-safe-assembly
assembly {
@ -73,15 +92,17 @@ library Base64 {
resultPtr := add(resultPtr, 1) // Advance
}
// When data `bytes` is not exactly 3 bytes long
// it is padded with `=` characters at the end
switch mod(mload(data), 3)
case 1 {
mstore8(sub(resultPtr, 1), 0x3d)
mstore8(sub(resultPtr, 2), 0x3d)
}
case 2 {
mstore8(sub(resultPtr, 1), 0x3d)
if withPadding {
// When data `bytes` is not exactly 3 bytes long
// it is padded with `=` characters at the end
switch mod(mload(data), 3)
case 1 {
mstore8(sub(resultPtr, 1), 0x3d)
mstore8(sub(resultPtr, 2), 0x3d)
}
case 2 {
mstore8(sub(resultPtr, 1), 0x3d)
}
}
}