Solidity provides an option to use assembly language to write inline assembly within Solidity source code. We can also write a standalone assembly code which then be converted to bytecode. Standalone Assembly is an intermediate language for a Solidity compiler and it converts the Solidity code into a Standalone Assembly and then to byte code. We can used the same language used in Inline Assembly to write code in a Standalone assembly.
Inline Assembly
Inline assembly code can be interleaved within Solidity code base to have more fine-grain control over EVM and is used especially while writing the library functions.
An assembly code is written under assembly { … } block.
Example
Try the following code to understand how a Library works in Solidity.
pragma solidity ^0.5.0; library Sum { function sumUsingInlineAssembly(uint[] memory _data) public pure returns (uint o_sum) { for (uint i = 0; i < _data.length; ++i) { assembly { o_sum := add(o_sum, mload(add(add(_data, 0x20), mul(i, 0x20)))) } } } } contract Test { uint[] data; constructor() public { data.push(1); data.push(2); data.push(3); data.push(4); data.push(5); } function sum() external view returns(uint){ return Sum.sumUsingInlineAssembly(data); } }
Run the above program using steps provided in chapter.
Note − Select Test from dropdown before clicking the deploy button.
Output
0: uint256: 15