Bytes32 与 String

在 Solidity 中，不同的数据存储类型的选择可能会在合约操作时带来不同的 gas 消耗，尤其是存储或修改状态变量时。 以太坊虚拟机（EVM）对所有操作收取燃气费，选择使用bytes32或 string类型会影响这些消耗。

代码演示

Below, we present two simple contracts, SetBytes32 and SetString, which illustrate the difference in gas usage when setting a bytes32 type versus a string type with the same content.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

contract SetBytes32 {
    bytes32 public b32;

    // use bytes32: 22222 gas
    function setBytes32() public {
        b32 = "Hello Conflux!";
    }
}

contract SetString {
    string public str;

    // use string: 22682 gas
    function setString() public {
        str = "Hello Conflux!";
    }
}

When deployed and executed, the SetBytes32 contract uses less gas (22,222 gas) compared to the SetString contract (22,682 gas). The difference, while not substantial, highlights how bytes32 is more gas-efficient for storing fixed-size data compared to string, which is designed for dynamically sized data.

关于节省燃气的详细说明

The choice between bytes32 and string in Solidity impacts gas consumption due to the differences in how each handles data storage:

• bytes32: 固定大小的数据类型，无论内容长度如何，固定占用32个字节。 Since bytes32 is fixed, there's no need for additional space to store data length, simplifying the contract's storage requirements. 在以太坊智能合约中，存储操作很昂贵，但是 bytes32通过紧凑地适应EVM的单个存储槽（恰好为32字节）优化这些操作。 This configuration allows for efficient read and write operations, minimizing gas costs.

• string: 动态大小的数据类型，每次存储时都需要额外存储长度信息。 这种动态特性带来了复杂性，string常常占用多个存储槽，特别是超过32字节时。 Managing these dynamic arrays increases computational demands for locating the start and end points of the data, leading to higher gas usage.

燃气优化建议:

对于长度不超过32字节的固定长度字符串，请使用bytes32，对于可变长度内容或长度可能超过32字节的情况，请使用string。

🌟 尽可能使用bytes32来存储固定大小的数据，以节省燃气消耗。