基本实现，但会在内存分配上翻车

work20220401/main.cpp

@@ -1,9 +1,13 @@
+#include <cstring>
 #include "iostream"
 #include "neoString/CString.h"
 
 using namespace std;
 
 int main() {
+//    char *p = new char[15]();
+//    strncpy(p, "asdf", 4);
+//    cout << p;
     int n, i, j;
     while (cin >> n) {
         CString *c = new CString[n + 2];

work20220401/neoString/CString.cpp

@@ -1,125 +1,171 @@
-//
-// Created by lenfrex on 2022/4/4.
-//
-
-#include <cstring>
-#include <algorithm>
-
-#include "CString.h"
-
-/*
- * 按照给定大小来初始化字符串数据
- */
-CString::CString(int length) {
-    data = new char[length]();
-    CString::length = length;
-}
-
-CString::~CString() {
-    delete[] data;
-}
-
-/*
- * 不设定初始化大小就默认512个字符来初始化
- */
-CString::CString() : CString(512) {}
-
-/*
- * 重载等号。借鉴了Java中String类的equal()方法的实现。
- * 首先比较两字符串长度，如果长度不一样不用说，直接返回false；如果data为nullptr，不做比较并返回false
- * 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
- * 两者都不同才进行逐字比较
- */
-bool CString::operator==(const CString &source) const {
-    // 判断两CString长度以及本对象data成员是否为空指针
-    if (source.length != length || data == nullptr) {
-        return false;
-    } else {
-        // 判断两对象data成员是否指向同一内存块
-        if (source.data == data) {
-            return true;
-        }
-    }
-
-    // 以上情况都不符合时才进行逐字比较
-    int compareLength = std::min(source.length, length);
-    for (int i = 0; i < compareLength; ++i) {
-        if (data[i] != source.data[i]) {
-            return false;
-        }
-    }
-    return true;
-}
-
-/*
- * 从源中复制字符串来构建新的对象
- */
-CString::CString(char *source) : CString((int)strlen(source)) {
-    strncpy(data, source, length);
-}
-
-/*
- * 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
- */
-CString::CString(char *source, int length) : CString(length) {
-    strncpy(data, source, length);
-}
-
-CString &CString::operator=(const CString &source) {
-    // 处理自己给自己赋值的情况，那叫啥，自赋值
-    if (this == &source) {
-        return *this;
-    }
-
-    if (data != nullptr && length != 0) {
-        delete[] data;
-    }
-
-    this->length = source.length;
-    this->data = new char[length]();
-
-    strncpy(data, source.data, length);
-
-    return *this;
-}
-
-CString &CString::operator+=(const CString &source) {
-    if (data == nullptr && length == 0) {
-        this->length = source.length;
-        this->data = new char[length]();
-    }
-
-    char *tmp = new char[length]();
-    strncpy(tmp, data, length);
-
-    // 重新分配内存，防止拼接后溢出
-    delete[] data;
-    this->length += source.length;
-    this->data = new char[this->length];
-
-    strcpy(tmp, data);
-    strncat(data, source.data, source.length);
-
-    return *this;
-}
-
-CString::CString(const CString &source) : CString(source.data, source.length) {}
-
-/*
- * 按照字典顺序逐字对比
- */
-bool CString::operator<(const CString &source) const {
-    // 这部分类似于前边==重载的前置判断，如果本对象数据为null或者两对象数据是一回事就直接false
-    if (data == nullptr || (source.length != length && source.data == data)) {
-        return false;
-    }
-
-    // 以上情况都不符合时才进行逐字比较
-    int compareLength = std::min(source.length, length);
-    for (int i = 0; i < compareLength; ++i) {
-        if (data[i] < source.data[i]) {
-            return true;
-        }
-    }
-    return false;
-}
+//
+// Created by lenfrex on 2022/4/4.
+//
+
+#include <cstring>
+#include <algorithm>
+
+#include "CString.h"
+
+/*
+ * 按照给定大小来初始化字符串数据
+ */
+CString::CString(int length) {
+    data = new char[length]();
+}
+
+CString::~CString() {
+    delete[] data;
+    data = nullptr;
+}
+
+/*
+ * 不设定初始化大小就默认512个字符来初始化
+ */
+CString::CString() : CString(512) {}
+
+/*
+ * 重载等号。借鉴了Java中String类的equal()方法的实现思路。
+ * 首先判断data是否为nullptr，同为null则true，否则就是false
+ * 再比较两字符串长度，如果长度不一样不用说，直接返回false；
+ * 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
+ * 两者都不同才进行逐字比较
+ */
+bool CString::operator==(const CString &source) const {
+    // 首先判断两CString对象data成员是否为空指针
+    if (source.data == nullptr || this->data == nullptr) {
+        return source.data == nullptr && this->data == nullptr;
+    }
+
+    int length = (int)strlen(data);
+    int sourceLength = (int)strlen(source.data);
+
+    // 字符串长度不等，字符串肯定是不等
+    if (length != sourceLength) {
+        return false;
+    } else {
+        // 长度相等且data指向相同肯定等
+        if (source.data == this->data) {
+            return true;
+        }
+    }
+
+    // 以上情况都不符合时才进行逐字比较
+    int compareLength = std::min(sourceLength, length);
+    for (int i = 0; i < compareLength; ++i) {
+        if (data[i] != source.data[i]) {
+            return false;
+        }
+    }
+    return true;
+}
+
+/*
+ * 从源中复制字符串来构建新的对象
+ */
+CString::CString(char *source) : CString((int)strlen(source)) {
+    strcpy(data, source);
+}
+
+/*
+ * 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
+ */
+CString::CString(char *source, int length) : CString(length) {
+    strncpy(data, source, length);
+}
+
+CString &CString::operator=(const CString &source) {
+    // 处理自己给自己赋值的情况，那叫啥，自赋值
+    if (this == &source) {
+        return *this;
+    }
+
+    delete[] data;
+
+    // 等号右侧空指针的话直接data赋为空指针
+    // 这里在执行前就已经delete掉data的数据了，不会泄漏
+    if (source.data == nullptr) {
+        this->data = nullptr;
+        return *this;
+    }
+
+    int sourceLength = (int)strlen(source.data);
+
+    this->data = new char[sourceLength]();
+    strcpy(data, source.data);
+
+    return *this;
+}
+
+CString &CString::operator+=(const CString &source) {
+    // nullptr不做处理
+    if(source.data == nullptr) {
+        return *this;
+    }
+
+    int sourceLength = (int)strlen(source.data);
+    int length = 0;
+
+    // 本对象nullptr的话就直接新分配
+    if (data == nullptr) {
+        this->data = new char[sourceLength]();
+        length = sourceLength;
+    } else {
+        length = (int)strlen(data);
+    }
+
+    // 保存拼接前的原数据，以便重新分配足够的内存
+    char *old = new char[length]();
+    strcpy(old, data);
+
+    // 重新分配内存，防止拼接后溢出
+    length += sourceLength;
+    delete[] data;
+    this->data = new char[length]();
+
+    strcpy(data, old);
+    strcat(data, "--");
+    strncat(data, source.data, sourceLength);
+
+    return *this;
+}
+
+CString::CString(const CString &source) : CString(source.data) {}
+
+/*
+ * 按照字典顺序逐字对比
+ */
+bool CString::operator>(const CString &source) const {
+    // 首先判断两CString对象data成员是否为空指针，空直接返回false
+    if (source.data == nullptr || this->data == nullptr) {
+        std::cout << "nullptr!"<< std::endl;
+        return false;
+    }
+
+    int length = (int)strlen(data);
+    int sourceLength = (int)strlen(source.data);
+
+    // 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"<"
+    if (sourceLength == length && source.data == this->data) {
+        std::cout << "memsame" << std::endl;
+        return false;
+    }
+
+    // 以上情况都不符合时才进行逐字比较
+    int compareLength = std::min(sourceLength, length);
+    for (int i = 0; i < compareLength; ++i) {
+        if (data[i] > source.data[i]) {
+            std::cout << "data[i]: " << data[i] << " source.data[i]: " << source.data[i] << std::endl;
+            return true;
+        }
+    }
+    return false;
+}
+
+std::ostream &operator<<(std::ostream &outputStream, const CString &source) {
+    return outputStream << source.data;
+}
+
+std::istream &operator>>(std::istream &inputStream, const CString &source) {
+    return inputStream >> source.data;
+}

work20220401/neoString/CString.h

@@ -5,13 +5,13 @@
 #ifndef WORK20220401_CSTRING_H
 #define WORK20220401_CSTRING_H
 
+#include <iostream>
 #include "utility"
 
 using namespace std::rel_ops;
 class CString {
 private:
     char *data = nullptr;
-    int length = 0;
 public:
     explicit CString(int length);
 
@@ -27,12 +27,14 @@ public:
 
     bool operator==(const CString &source) const;
 
-    bool operator<(const CString &source) const;
+    bool operator>(const CString &source) const;
 
     CString &operator+=(const CString &source);
 
     CString &operator=(const CString &source);
-};
 
+    friend std::ostream &operator<<(std::ostream &outputStream, const CString &source);
+    friend std::istream &operator>>(std::istream &outputStream, const CString &source);
+};
 
 #endif //WORK20220401_CSTRING_H