Merge pull request #818 from smallfu6/feature/optimize-abi-encode

Closes #782:  optimize ABI encoding

27_ABIEncode/readme.md

@@ -45,7 +45,19 @@ function encode() public view returns(bytes memory result) {
 }
 ```
 
-编码的结果为`0x000000000000000000000000000000000000000000000000000000000000000a0000000000000000000000007a58c0be72be218b41c608b7fe7c5bb630736c7100000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000005000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000043078414100000000000000000000000000000000000000000000000000000000`，由于`abi.encode`将每个数据都填充为32字节，中间有很多`0`。
+编码的结果为`0x000000000000000000000000000000000000000000000000000000000000000a0000000000000000000000007a58c0be72be218b41c608b7fe7c5bb630736c7100000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000005000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000043078414100000000000000000000000000000000000000000000000000000000`，详细解释下编码的细节：
+
+```
+000000000000000000000000000000000000000000000000000000000000000a    // x
+0000000000000000000000007a58c0be72be218b41c608b7fe7c5bb630736c71    // addr
+00000000000000000000000000000000000000000000000000000000000000a0    // name 参数的偏移量
+0000000000000000000000000000000000000000000000000000000000000005    // array[0]
+0000000000000000000000000000000000000000000000000000000000000006    // array[1]
+0000000000000000000000000000000000000000000000000000000000000004    // name 参数的长度为4字节
+3078414100000000000000000000000000000000000000000000000000000000    // name
+```
+
+其中 `name` 参数被转换为UTF-8的字节值 `0x30784141`，在 abi 编码规范中，string 属于动态类型 ，动态类型的参数需要借助偏移量进行编码，可以参考[动态类型的使用](https://learnblockchain.cn/docs/solidity/abi-spec.html#id9)。由于 abi.encode 会将每个参与编码的参数元素（包括偏移量，长度）都填充为32字节（evm字长为32字节），所以可以看到编码后的数据中有很多填充的 0 。
 
 ### `abi.encodePacked`