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//
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// Created by lenfrex on 2022/4/4.
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//
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#include <cstring>
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#include <algorithm>
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#include "CString.h"
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/*
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* 按照给定大小来初始化字符串数据
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*/
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CString::CString(int length) {
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data = new char[length]();
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}
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CString::~CString() {
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delete[] data;
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data = nullptr;
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}
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/*
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* 不设定初始化大小就默认512个字符来初始化
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*/
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CString::CString() : CString(512) {}
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/*
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* 重载等号。借鉴了Java中String类的equal()方法的实现思路。
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* 首先判断data是否为nullptr,同为null则true,否则就是false
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* 再比较两字符串长度,如果长度不一样不用说,直接返回false;
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* 相同的话再比较两字符串数据指针指向地址是否一样,一样就代表指向的是同一块内存,直接返回true
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* 两者都不同才进行逐字比较
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*/
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bool CString::operator==(const CString &source) const {
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// 首先判断两CString对象data成员是否为空指针
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if (source.data == nullptr || this->data == nullptr) {
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return source.data == nullptr && this->data == nullptr;
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}
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int length = (int)strlen(data);
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int sourceLength = (int)strlen(source.data);
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// 字符串长度不等,字符串肯定是不等
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if (length != sourceLength) {
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return false;
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} else {
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// 长度相等且data指向相同肯定等
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if (source.data == this->data) {
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return true;
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}
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}
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// 以上情况都不符合时才进行逐字比较
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int compareLength = std::min(sourceLength, length);
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for (int i = 0; i < compareLength; ++i) {
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if (data[i] != source.data[i]) {
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return false;
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}
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}
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return true;
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}
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/*
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* 从源中复制字符串来构建新的对象
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*/
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CString::CString(char *source) : CString((int)strlen(source)) {
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strcpy(data, source);
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}
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/*
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* 从源中复制字符串来构建新的对象,并定义初始长度,小于源字符串则会被截取
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*/
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CString::CString(char *source, int length) : CString(length) {
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strncpy(data, source, length);
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}
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CString &CString::operator=(const CString &source) {
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// 处理自己给自己赋值的情况,那叫啥,自赋值
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if (this == &source) {
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return *this;
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}
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delete[] data;
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// 等号右侧空指针的话直接data赋为空指针
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// 这里在执行前就已经delete掉data的数据了,不会泄漏
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if (source.data == nullptr) {
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this->data = nullptr;
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return *this;
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}
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int sourceLength = (int)strlen(source.data);
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this->data = new char[sourceLength]();
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strcpy(data, source.data);
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return *this;
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}
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CString &CString::operator+=(const CString &source) {
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// nullptr不做处理
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if(source.data == nullptr) {
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return *this;
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}
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int sourceLength = (int)strlen(source.data);
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int length = 0;
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// 本对象nullptr的话就直接新分配
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if (data == nullptr) {
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this->data = new char[sourceLength]();
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length = sourceLength;
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} else {
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length = (int)strlen(data);
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}
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// 保存拼接前的原数据,以便重新分配足够的内存
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char *old = new char[length]();
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strcpy(old, data);
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// 重新分配内存,防止拼接后溢出
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length += sourceLength;
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delete[] data;
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this->data = new char[length]();
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strcpy(data, old);
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strcat(data, "--");
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strncat(data, source.data, sourceLength);
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return *this;
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}
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CString::CString(const CString &source) : CString(source.data) {}
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/*
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* 按照字典顺序逐字对比
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*/
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bool CString::operator>(const CString &source) const {
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// 首先判断两CString对象data成员是否为空指针,空直接返回false
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if (source.data == nullptr || this->data == nullptr) {
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std::cout << "nullptr!"<< std::endl;
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return false;
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}
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int length = (int)strlen(data);
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int sourceLength = (int)strlen(source.data);
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// 两对象指向data同一内存区域并且长度相等则可以判断两字符串相等,所以就不是"<"
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if (sourceLength == length && source.data == this->data) {
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std::cout << "memsame" << std::endl;
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return false;
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}
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// 以上情况都不符合时才进行逐字比较
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int compareLength = std::min(sourceLength, length);
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for (int i = 0; i < compareLength; ++i) {
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if (data[i] > source.data[i]) {
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std::cout << "data[i]: " << data[i] << " source.data[i]: " << source.data[i] << std::endl;
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return true;
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}
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}
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return false;
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}
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std::ostream &operator<<(std::ostream &outputStream, const CString &source) {
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return outputStream << source.data;
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}
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std::istream &operator>>(std::istream &inputStream, const CString &source) {
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return inputStream >> source.data;
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}
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