Base64编解码库 (#81)

Author: Kesling515

contracts/common_tools/LibBase64.sol

@@ -0,0 +1,126 @@
+pragma solidity ^0.4.25;
+
+library LibBase64 {
+
+ bytes constant private base64stdchars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
+
+ /**
+ * 字符串 base64 编码
+ *
+ * @ param data 要解码的数据
+ * @ return 经 base64 返回的编码数据
+ *
+ **/
+ function encode(string memory data) internal pure returns(string memory) {
+ uint i = 0; 
+ uint j = 0;
+
+ uint padlen = bytes(data).length; 
+ if (padlen % 3 != 0) 
+ padlen += (3 - (padlen % 3));
+
+ bytes memory _bs = bytes(data);
+ bytes memory _ms = new bytes(padlen); 
+ 
+ for (i = 0; i < _bs.length; i++) { 
+ _ms[i] = _bs[i];
+ }
+ 
+ // 计算编码后的字符长度
+ uint res_length = (padlen / 3) * 4; 
+ bytes memory res = new bytes(res_length); 
+ for (i = 0; i < padlen; i += 3) {
+ // 取第一字符 _ms[i] 的前 6 比特位作为 base64 字符 0 的索引
+ uint c0 = uint(uint8(_ms[i])) >> 2;
+ // 取 _ms[i] 的后2位，在末尾补 _ms[i+1] 的前 4 位作为 base64 字符 1 的索引
+ uint c1 = (uint(uint8(_ms[i])) & 3) << 4 | uint(uint8(_ms[i+1])) >> 4;
+ // 取 _ms[i+1] 的后 4 位，在末尾补 _ms[i+2] 的前 2 位作为 base64 字符 2 的索引
+ uint c2 = (uint(uint8(_ms[i+1])) & 15) << 2 | uint(uint8(_ms[i+2])) >> 6;
+ // 取 _ms[i+2] 的后 6 位作为 base64 字符 3 的索引
+ uint c3 = (uint(uint8(_ms[i+2])) & 63);
+
+ res[j] = base64stdchars[c0];
+ res[j+1] = base64stdchars[c1];
+ res[j+2] = base64stdchars[c2];
+ res[j+3] = base64stdchars[c3];
+
+ j += 4;
+ }
+
+ // 判断是否要补位，即 + 0 ，补位则设置索引为 64，对应 ‘=’ 字符
+ if ((padlen - bytes(data).length) >= 1) { 
+ res[j-1] = base64stdchars[64];
+ }
+ if ((padlen - bytes(data).length) >= 2) { 
+ res[j-2] = base64stdchars[64];
+ }
+
+ return string(res);
+ }
+
+ /**
+ * 字符串 base64 解码
+ *
+ * @ param data 要解码的数据
+ * @ return 返回的解码数据
+ *
+ **/
+ function decode(string memory data) internal pure returns(string memory) {
+ require((bytes(data).length % 4) == 0, "Length not multiple of 4");
+ bytes memory _bs = bytes(data);
+
+ uint i = 0;
+ uint j = 0;
+ uint dec_length = (_bs.length / 4) * 3;
+ bytes memory dec = new bytes(dec_length);
+
+ for (; i< _bs.length; i+=4) {
+ (dec[j], dec[j+1], dec[j+2]) = dencode4(
+ bytes1(_bs[i]),
+ bytes1(_bs[i+1]),
+ bytes1(_bs[i+2]),
+ bytes1(_bs[i+3])
+ );
+ j += 3;
+ }
+ while (dec[--j]==0) {}
+
+ bytes memory res = new bytes(j+1);
+ for (i=0; i<=j; i++)
+ res[i] = dec[i];
+
+ return string(res);
+ }
+
+ // 将4个base64编码字符解码为原3个字符
+ function dencode4 (
+ bytes1 b0, 
+ bytes1 b1, 
+ bytes1 b2, 
+ bytes1 b3
+ ) 
+ private 
+ pure
+ returns (bytes1 a0, bytes1 a1, bytes1 a2)
+ {
+ uint pos0 = charpos(b0);
+ uint pos1 = charpos(b1);
+ uint pos2 = charpos(b2) % 64;
+ uint pos3 = charpos(b3) % 64;
+
+ // 取 b0 + b1 的前2位组成 8 比特位即 1 字节
+ a0 = bytes1(uint8((pos0 << 2 | pos1 >> 4)));
+ // 取 b1 后 4 位 + b2 的前 4 位组成 8 比特位即 1 字节
+ a1 = bytes1(uint8(((pos1 & 15) << 4 | pos2 >> 2)));
+ // 取 b2 前 2 位 + b3 组成 8 比特位即 1 字节
+ a2 = bytes1(uint8(((pos2 & 3) << 6 | pos3)));
+ }
+
+ // 检查是否是 base64 字符，返回字符索引
+ function charpos(bytes1 char) private pure returns (uint pos) {
+ for (; base64stdchars[pos] != char; pos++) {}
+ require (base64stdchars[pos] == char, "Illegal char in string");
+ return pos;
+ }
+
+}

contracts/common_tools/LibBase64Test.sol

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+pragma solidity ^0.4.25;
+import "./LibBase64.sol";
+
+contract LibBase64 {
+ function test_encode() public pure returns (string memory) {
+ string memory _str = "hello world";
+ return LibBase64.encode(_str);
+ }
+
+ function test_decode() public pure returns (string memory) {
+ string memory _str = "aGVsbG8gd29ybGQ=";
+ return LibBase64.decode(_str);
+ }
+}

docs/common_tools/LibBase64.md

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+# LibBase64.sol
+
+LibBase64 提供Base64编解码
+
+
+## 接口说明
+1. function encode(string memory data) returns(string memory)：Base64编码
+- data：要编码的数据
+
+2. function decode(string memory data) returns(string memory)：Base64解码
+- data：要解码的数据
+
+## 使用方法
+
+```
+pragma solidity ^0.4.25;
+import "./LibBase64.sol";
+
+contract LibBase64 {
+ function test_encode() public pure returns (string memory) {
+ string memory _str = "hello world";
+ return LibBase64.encode(_str);
+ }
+
+ function test_decode() public pure returns (string memory) {
+ string memory _str = "aGVsbG8gd29ybGQ=";
+ return LibBase64.decode(_str);
+ }
+}
+
+```