[转]陈硕10分钟搞定string

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#pragma once#include <utility>#include <assert.h>#include <string.h>namespace trivial{// A trivial String class that designed for write-on-paper in an interviewclass String{ public:  String()    : data_(new char[1])  {    *data_ = '\0';  }  String(const char* str)    : data_(new char[strlen(str) + 1])  {    strcpy(data_, str);  }  String(const String& rhs)    : data_(new char[rhs.size() + 1])  {    strcpy(data_, rhs.c_str());  }  /* Implement copy-ctor with delegating constructor in C++11  String(const String& rhs)    : String(rhs.data_)  {  }  */  ~String() noexcept  {    delete[] data_;  }  /* Traditional:  String& operator=(const String& rhs)  {    String tmp(rhs);    swap(tmp);    return *this;  }  */  // In C++11, this is unifying assignment operator  String& operator=(String rhs) // yes, pass-by-value  {    // http://en.wikibooks.org/wiki/More_C++_Idioms/Copy-and-swap    swap(rhs);    return *this;  }  // C++11 move-ctor  String(String&& rhs) noexcept    : data_(rhs.data_)  {    rhs.data_ = nullptr;  }  /* Not needed if we have pass-by-value operator=() above,   * and it conflits. http://stackoverflow.com/questions/17961719/  String& operator=(String&& rhs)  {    swap(rhs);    return *this;  }  */  // Accessors  size_t size() const  {    return strlen(data_);  }  const char* c_str() const  {    return data_;  }  void swap(String& rhs)  {    std::swap(data_, rhs.data_);  } private:  char* data_;};}namespace trivial2{// string in C++11 with a length memberclass String{ public:  String() noexcept    : data_(nullptr), len_(0)  { }  ~String()  {    delete[] data_;  }  // only read str when len > 0  String(const char* str, size_t len)    : data_(len > 0 ? new char[len+1] : nullptr), len_(len)  {    if (len_ > 0)    {      memcpy(data_, str, len_);      data_[len_] = '\0';    }    else    {      assert(data_ == nullptr);    }  }  String(const char* str)    : String(str, strlen(str))  { }  String(const String& rhs)    : String(rhs.data_, rhs.len_)  { }  String(String&& rhs) noexcept    : data_(rhs.data_), len_(rhs.len_)  {    rhs.len_ = 0;    rhs.data_ = nullptr;  }  String& operator=(String rhs)  {    swap(rhs);    return *this;  }  void swap(String& rhs) noexcept  {    std::swap(len_, rhs.len_);    std::swap(data_, rhs.data_);  }  // const char* data() const { return c_str(); }  const char* c_str() const noexcept { return data_ ? data_ : kEmpty; }  size_t size() const noexcept { return len_; } private:  char* data_;  size_t len_;  static const char kEmpty[];};// const char String::kEmpty[] = "";}
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