本文节选自电子书《Netkiller Blockchain 手札》
Netkiller Blockchain 手札
本文作者最近在找工作，有意向致电 13113668890
Mr. Neo Chan, 陈景峯(BG7NYT)
中国广东省深圳市龙华新区民治街道溪山美地
518131
+86 13113668890
<netkiller@msn.com>
文档始创于2018-02-10
版权 © 2018 Netkiller(Neo Chan). All rights reserved.
版权声明
转载请与作者联系，转载时请务必标明文章原始出处和作者信息及本声明。
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4.5. 数据类型
4.5.1. 数值型
int/uint：变长的有符号或无符号整型。变量支持的步长以8递增，支持从uint8到uint256，以及int8到int256。需要注意的是，uint和int默认代表的是uint256和int256。
有符号整型能够表示负数的代价是其能够存储正数的范围的缩小，因为其约一半的数值范围要用来表示负数。如：uint8的存储范围为0 ~ 255，而int8的范围为-127 ~ 127
支持的运算符:
比较：<=，<，==，!=，>=，>，返回值为bool类型。
位运算符：&，|，（^异或），（~非）。
数学运算：+，-，一元运算+，*，/，（%求余），（**次方），（<<左移），（>>右移）。
小数由"."组成，在他的左边或右边至少要包含一个数字。如"1."，".1"，"1.3"均是有效的小数。
4.5.1.1. 加 +，减 -，乘 *，除 ／ 运算演示
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract Math {
function mul(int a, int b) public pure returns (int) {
int c = a * b;
return c;
}
function div(int a, int b) public pure returns (int) {
int c = a / b;
return c;
}
function sub(int a, int b) public pure returns (int) {
return a - b;
}
function add(int a, int b) public pure returns (int) {
int c = a + b;
return c;
}
}
4.5.1.2. 求余 %
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract Math {
function m(int a, int b) public pure returns (int) {
int c = a % b;
return c;
}
}
4.5.1.3. 幂运算
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract Math {
function m(uint a, uint b) public pure returns (uint) {
uint c = a**b;
return c;
}
}
4.5.1.4. 与 &，| 或，非 ～，^ 异或
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract Math {
function yu() public pure returns (uint) {
uint a = 3; // 0b0011
uint b = 4; // 0b0100
uint c = a & b; // 0b0000
return c; // 0
}
function huo() public pure returns (uint) {
uint a = 3; // 0b0011
uint b = 4; // 0b0100
uint c = a | b; // 0b0111
return c; // 7
}
function fei() public pure returns (uint8) {
uint8 a = 3; // 0b00000011
uint8 c = ~a; // 0b11111100
return c; // 0
}
function yihuo() public pure returns (uint) {
uint a = 3; // 0b0011
uint b = 4; // 0b0100
uint c = a ^ b; // 0b0111
return c; // 252
}
}
4.5.1.5. 位移
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract Math {
function leftShift() public pure returns (uint8) {
uint8 a = 8; // 0b00001000
uint8 c = a << 2; // 0b00100000
return c; // 32
}
function rightShift() public pure returns (uint8) {
uint8 a = 8; // 0b00001000
uint8 c = a >> 2; // 0b00000010
return c; // 2
}
}
a << n 表示a的二进制位向左移动n位，在保证位数没有溢出的情况下等价于 a乘以2的n次方。
a >> n 表示a的二进制位向右移动n位，在保证位数没有溢出的情况下等价于 a除以2的n次方。
4.5.2. 字符串
string 字符串类型，字符串可以通过""或者''来定义字符串的值
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract StringTest {
string name;
function StringTest() public{
name = "default";
}
function setName(string _name) public{
name = _name;
}
function getName() public view returns(string){
return name;
}
}
4.5.2.1. 获取字符串长度
在 Solidity 中想获得字符串长度必须转成 bytes 类型然后使用 length 属性获得。bytes(string).length
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract StringTest {
string public name = "http://www.netkiller.cn";
function nameBytes() public constant returns (bytes) {
return bytes(name);
}
function nameLength() public constant returns (uint) {
return bytes(name).length;
}
function length(string _name) public pure returns (uint) {
return bytes(_name).length;
}
}
![[提示]](https://ucc.alicdn.com/notfound.png?x-oss-process=image/resize,w_1400/format,webp) |
提示 |
|---|---|
注意：汉字采用UTF8编码，一个汉字等于3个字节，当你使用 length("景峯") 测试时会返回长度 6。 |
4.5.3. 布尔(Booleans)
bool: 可能的取值为常量值true和false。支持的运算符：
! 逻辑非
&& 逻辑与
|| 逻辑或
== 等于
!= 不等于
bool a = true;
bool b = !a;
// a == b -> false
// a != b -> true
// a || b -> true
// a && b -> false
4.5.4. 字节类型
bytes names = "netkiller"
bytes9 _names = "netkiller";
bytes(name)[0] = 0xFF;
bytes memory _tmp = new bytes(3);
_tmp[0] = 0x4e;
_tmp[1] = 0x65;
_tmp[2] = 0x6f;
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract BytesTest {
bytes names = "netkiller";
function get() public view returns (bytes) {
return names;
}
function getBytes2() public pure returns (bytes2) {
bytes9 _names = "netkiller";
return bytes2(_names);
}
function bytesToString() public constant returns (string) {
return string(names);
}
function copyBytes(bytes b) public pure returns (bytes) {
bytes memory tmp = new bytes(b.length);
for(uint i = 0; i < b.length; i++) {
tmp[i] = b[i];
}
return tmp;
}
function bytesToString2() public pure returns (string) {
bytes memory _tmp = new bytes(3);
_tmp[0] = 0x4e;
_tmp[1] = 0x65;
_tmp[2] = 0x6f;
return string(_tmp);
}
}
.length可以动态修改字节数组的长度
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract BytesTest2 {
// 初始化一个两个字节空间的字节数组
bytes public array = new bytes(2);
// 设置修改字节数组的长度
function setLength(uint _len) public {
array.length = _len;
}
// 返回字节数组的长度
function getLength() constant public returns (uint) {
return array.length;
}
// 往字节数组中添加字节
function pushArray(byte _tmp) public{
array.push(_tmp);
}
}
4.5.5. 数组
//创建一个memory的数组
uint[] memory a = new uint[](7);
uint[] x = [uint(1), 3, 4];
bytes memory b = new bytes(10);
二维数组
uint [2][3] T = [[1,2],[3,4],[5,6]];
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract ArrayTest {
uint [] array = [1,2,3,4,5];
// 通过for循环计算数组内部的值的总和
function sum() constant public returns (uint) {
uint num = 0;
for(uint i = 0; i < array.length; i++) {
num = num + array[i];
}
return num;
}
function sumNumbers(uint[] _numbers) public pure returns (uint) {
uint num = 0;
for(uint i = 0; i < _numbers.length; i++) {
num = num + _numbers[i];
}
return num;
}
}
4.5.5.1. length
.length 属性是活动数组的尺寸
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract ArrayLength {
uint [] array = [1,2,3,4,5];
function getLength() public constant returns (uint) {
return array.length;
}
}
4.5.5.2. push() 方法
通过 push 可以向数组中添加数据
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract ArrayLength {
uint [] array = [1,2,3,4,5];
function pushArray() public {
array.push(6);
}
function getLength() public constant returns (uint) {
return array.length;
}
}
4.5.6. 枚举类型
State 就是一个自定义的整型，当枚举数不够多时，它默认的类型为uint8，当枚举数足够多时，它会自动变成uint16，枚举下标定义从左至右从零开始。
New=0, Pending=1, Done=2, Deleted=3
访问枚举方式 State.New 实际等于数字 0
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract EnumTest {
enum State { New, Pending, Done, Deleted }
State state = State.New;
function set(State _state) public {
state = _state;
}
function get() constant public returns (State) {
return state;
}
}
枚举用来定义状态
pragma solidity ^0.4.0;
contract Purchase {
enum State { Created, Locked, Inactive } // Enum
}
4.5.7. 结构体
定义结构体
struct Voter {
uint weight; // weight is accumulated by delegation
bool voted; // if true, that person already voted
address delegate; // person delegated to
uint vote; // index of the voted proposal
}
// This is a type for a single proposal.
struct Proposal {
bytes32 name; // short name (up to 32 bytes)
uint voteCount; // number of accumulated votes
}
演示例子
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract Students {
struct Person {
string name;
uint age;
uint class;
}
Person person = Person("Neo",18,1);
function getPerson() public view returns(string){
return person.name;
}
}
4.5.8. address
address public minter;
下面是一个获得账号余额的例子。
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract AddressTest{
function getBalance(address _addr) public constant returns (uint){
return _addr.balance;
}
}
4.5.8.1. payable
4.5.8.2. .value()
4.5.8.3. .gas()
4.5.9. mapping
mapping 就是图数据结构，由 key 和 value 组成。
pragma solidity ^0.4.20;
//Author: netkiller <netkiller@msn.com>
//Home: http://www.netkiller.cn
contract MappingExample {
mapping(uint => string) map;
function put(uint key, string value) public {
map[key] = value;
}
function get(uint key) constant public returns (string) {
return map[key];
}
}