#pragma once#include <cstddef> #include <cstring> #include <algorithm> #include <stdexcept>// namespace M { class string { public:static const size_t s_min_capacity; private:char* data_; // 字符串数据size_t size_; // 字符串长度size_t capacity_; // 容量// 重新分配内存的辅助函数void realloc_data(size_t new_cap) {new_cap = std::max(new_cap, s_min_capacity);char* new_data = new char[new_cap + 1];if (size_ > 0) {std::memcpy(new_data, data_, size_);}new_data[size_] = '\0';delete[] data_;data_ = new_data;capacity_ = new_cap; // capacity_存储用户数据容量 }public:// 默认构造函数string() : size_(0), capacity_(s_min_capacity) {data_ = new char[capacity_ + 1];data_[0] = '\0';}// 从C风格字符串构造string(const char* str) {if (!str) {throw std::invalid_argument("null pointer");}size_ = std::strlen(str);capacity_ = std::max(size_, s_min_capacity);data_ = new char[capacity_ + 1];std::memcpy(data_, str, size_ + 1);}// 二进制安全的构造函数string(const void* data, size_t len) {if (!data) {throw std::invalid_argument("null pointer");}size_ = len;capacity_ = std::max(len, s_min_capacity);data_ = new char[capacity_ + 1];std::memcpy(data_, data, len);data_[len] = '\0';}// 拷贝构造函数string(const string& other) : size_(other.size_), capacity_(other.capacity_) {data_ = new char[capacity_ + 1];std::memcpy(data_, other.data_, size_ + 1);}// 移动构造函数string(string&& other) noexcept : data_(other.data_), size_(other.size_), capacity_(other.capacity_) {other.data_ = nullptr;other.size_ = 0;other.capacity_ = 0;}// 析构函数~string() {delete[] data_;}// 拷贝赋值运算符string& operator=(const string& other) {if (this != &other) {char* new_data = new char[other.capacity_ + 1];std::memcpy(new_data, other.data_, other.size_ + 1);delete[] data_;data_ = new_data;size_ = other.size_;capacity_ = other.capacity_;}return *this;}// 移动赋值运算符string& operator=(string&& other) noexcept {if (this != &other) {delete[] data_;data_ = other.data_;size_ = other.size_;capacity_ = other.capacity_;other.data_ = nullptr;other.size_ = 0;other.capacity_ = 0;}return *this;}// 预分配内存void reserve(size_t new_cap) {if (new_cap > capacity_) {realloc_data(new_cap);}}// 释放多余内存void shrink_to_fit() {if (capacity_ > size_) {realloc_data(size_);}}// append 函数string& append(const char* str, size_t len) {if (!str) throw std::invalid_argument("null pointer");if (size_ + len > capacity_) {reserve((size_ + len) * 2);}std::memcpy(data_ + size_, str, len);size_ += len;data_[size_] = '\0';return *this;}string& append(const char* str) {if (!str) throw std::invalid_argument("null pointer");return append(str, std::strlen(str));}// 获取数据const char* c_str() const noexcept { return data_; }const char* data() const noexcept { return data_; }size_t size() const noexcept { return size_; }size_t capacity() const noexcept { return capacity_; }bool empty() const noexcept { return size_ == 0; } }; // } // namespace M const size_t string::s_min_capacity = 15;
测试：
#include <cassert> #include <iostream> #include <cstring> #include "string.h"// 用于测试的辅助函数 #define TEST_CASE(name) \do { \std::cout << "Running test case: " << #name << "... "; \test_##name(); \std::cout << "PASSED" << std::endl; \} while (0)// 测试构造函数 void test_constructors() {// 默认构造string s1;assert(s1.empty());assert(s1.size() == 0);assert(s1.capacity() == 15);assert(s1.c_str()[0] == '\0');// C风格字符串构造string s2("hello");assert(s2.size() == 5);assert(s2.capacity() >= 5);assert(strcmp(s2.c_str(), "hello") == 0);// 二进制安全构造char data[] = {'H', 'e', 'l', 'l', 'o', '\0', 'W', 'o', 'r', 'l', 'd'};string s3(data, 11);assert(s3.size() == 11);assert(memcmp(s3.data(), data, 11) == 0);// nullptr 检查try {string s4(nullptr);assert(false); // 不应该到达这里} catch (const std::invalid_argument&) {// 预期的异常 } }// 测试拷贝操作 void test_copy_operations() {string s1("hello");// 拷贝构造string s2(s1);assert(strcmp(s2.c_str(), "hello") == 0);assert(s1.c_str() != s2.c_str()); // 深拷贝检查// 拷贝赋值string s3;s3 = s1;assert(strcmp(s3.c_str(), "hello") == 0);assert(s1.c_str() != s3.c_str()); // 深拷贝检查 }// 测试移动操作 void test_move_operations() {// 移动构造string s1("hello");const char* original_data = s1.c_str();string s2(std::move(s1));assert(s2.c_str() == original_data); // 数据被移动assert(s1.empty()); // s1 被清空assert(s1.c_str() == nullptr); // s1 的指针被置空// 移动赋值string s3;s3 = std::move(s2);assert(s3.c_str() == original_data); // 数据被移动assert(s2.empty()); // s2 被清空assert(s2.c_str() == nullptr); // s2 的指针被置空 }// 测试容量管理 void test_capacity_management() {string s;assert(s.capacity() == 15); // 初始容量 s.reserve(20);assert(s.capacity() >= 20);s.append("hello");size_t cap = s.capacity();s.shrink_to_fit();assert(s.capacity() == 15); // 回到最小容量 }// 测试 append 操作 void test_append_operations() {string s;// 普通appends.append("hello");assert(strcmp(s.c_str(), "hello") == 0);// 触发扩容的appends.append(" world");assert(strcmp(s.c_str(), "hello world") == 0);// 二进制数据appendchar binary[] = {'!', '\0', '!'};s.append(binary, 3);assert(s.size() == 14);assert(memcmp(s.data() + 11, binary, 3) == 0); }// 测试边界条件 void test_edge_cases() {// 空字符串string s1("");assert(s1.size() == 0);assert(s1.c_str()[0] == '\0');// 大量数据std::string long_str(1000, 'x');string s2(long_str.c_str());assert(s2.size() == 1000);assert(memcmp(s2.data(), long_str.c_str(), 1000) == 0); }// 测试异常安全性 void test_exception_safety() {// 测试空指针try {string s1(nullptr);assert(false);} catch (const std::invalid_argument&) {}try {string s2;s2.append(nullptr);assert(false);} catch (const std::invalid_argument&) {} }int main() {TEST_CASE(constructors);TEST_CASE(copy_operations);TEST_CASE(move_operations);TEST_CASE(capacity_management);TEST_CASE(append_operations);TEST_CASE(edge_cases);TEST_CASE(exception_safety);std::cout << "\nAll tests passed!" << std::endl;return 0; }