C++ sample code to implement the encoding transformation

The code address

https://github.com/gongluck/Code-snippet/tree/master/cpp/code%20conversion

demand

Coding transformations are encountered frequently in practical development, usually between ANSI, Unicode, and Utf-8. There are many implementations, such as table lookup, C++11, boost, and system API. C++11 and boost can implement almost one set of code, which can be used in both linux and windows, but in practice there will be a lot of holes, equivalent to the code is almost unchanged, but the system environment has to be changed 1. So one implementation is to determine the version of the system and then select a different system, api, for the encoding conversion.

implementation

At present, only the encoding conversion under Windows is implemented, and will need to be supplemented with the encoding conversion under linux in the future. The coding transformation under windows is basically processed around unicode. For example ANSI - > So UTF-8, that's ANSI- > unicode, then unicode- > UTF - 8.

// convert.h
/*
 * @Author: gongluck 
 * @Date: 2020-03-23 16:06:23 
 * @Last Modified by: gongluck
 * @Last Modified time: 2020-03-23 16:09:30
 */

// Character encoding conversion

#pragma once

#include <string>

namespace gconvert
{
// ANSI->Unicode
int ansi2uni(const std::string& ansi, std::wstring& uni);

// Unicode->ANSI
int uni2ansi(const std::wstring& uni, std::string& ansi);

// UTF8->Unicode
int utf82uni(const std::string& utf8, std::wstring& uni);

// Unicode->UTF8
int uni2utf8(const std::wstring& uni, std::string& utf8);

// ANSI->UTF8
int ansi2utf8(const std::string& ansi, std::string& utf8);

// UTF8->ANSI
int utf82ansi(const std::string& utf8, std::string& ansi);
} // namespace gconvert

//convert.cpp
/*
 * @Author: gongluck 
 * @Date: 2020-03-23 16:13:01 
 * @Last Modified by: gongluck
 * @Last Modified time: 2020-03-23 16:34:50
 */

#include "convert.h"

#include <iostream>

#ifdef _WIN32
#include <windows.h>
#endif

namespace gconvert
{
#ifdef _WIN32
 static int multi2uni(const std::string& multi, std::wstring& uni, UINT code)
 {
  auto len = MultiByteToWideChar(code, 0, multi.c_str(), -1, nullptr, 0);
  if (len <= 0)
  {
   std::cerr << __FILE__ << " : " << __LINE__ << " : " << GetLastError() << std::endl;
   return -1;
  }
  WCHAR* buf = new WCHAR[len];
  if (buf == nullptr)
  {
   std::cerr << __FILE__ << " : " << __LINE__ << " : " << "can not new buf, size : " << len << std::endl;
   return -2;
  }
  len = MultiByteToWideChar(code, 0, multi.c_str(), -1, buf, len);
  uni.assign(buf);
  delete[]buf;
  buf = nullptr;
  return len;
 }

 static int uni2multi(const std::wstring& uni, std::string& multi, UINT code)
 {
  auto len = WideCharToMultiByte(code, 0, uni.c_str(), -1, nullptr, 0, nullptr, nullptr);
  if (len <= 0)
  {
   std::cerr << __FILE__ << " : " << __LINE__ << " : " << GetLastError() << std::endl;
   return -1;
  }
  CHAR* buf = new CHAR[len];
  if (buf == nullptr)
  {
   std::cerr << __FILE__ << " : " << __LINE__ << " : " << "can not new buf, size : " << len << std::endl;
   return -2;
  }
  len = WideCharToMultiByte(code, 0, uni.c_str(), -1, buf, len, nullptr, nullptr);
  multi.assign(buf);
  delete[]buf;
  buf = nullptr;
  return len;
 }
#endif

// ANSI->Unicode
int ansi2uni(const std::string& ansi, std::wstring& uni)
{
#ifdef _WIN32
 return multi2uni(ansi, uni, CP_ACP);
#endif
 return 0;
}

// Unicode->ANSI
int uni2ansi(const std::wstring &uni, std::string &ansi)
{
#ifdef _WIN32
 return uni2multi(uni, ansi, CP_ACP);
#endif
 return 0;
}

// UTF8->Unicode
int utf82uni(const std::string& utf8, std::wstring& uni)
{
#ifdef _WIN32
 return multi2uni(utf8, uni, CP_UTF8);
#endif
 return 0;
}

// Unicode->UTF8
int uni2utf8(const std::wstring& uni, std::string& utf8)
{
#ifdef _WIN32
 return uni2multi(uni, utf8, CP_UTF8);
#endif
 return 0;
}

// ANSI->UTF8
int ansi2utf8(const std::string &ansi, std::string &utf8)
{
 std::wstring uni;
 auto len = ansi2uni(ansi, uni);
 if (len <= 0)
 {
  return -3;
 }
 return uni2utf8(uni, utf8);
}

// UTF8->ANSI
int utf82ansi(const std::string &utf8, std::string &ansi)
{
 std::wstring uni;
 auto len = utf82uni(utf8, uni);
 if (len <= 0)
 {
  return -3;
 }
 return uni2ansi(uni, ansi);
}
} // namespace gconvert

//testcode
#include <iostream>

#include "../code conversion/convert.h"

int main()
{
 std::string ansi = " Hello, world! ";
 std::wstring uni;
 std::string utf8;
 ret = gconvert::ansi2uni(ansi, uni);
 ret = gconvert::ansi2utf8(ansi, utf8);
 ret = gconvert::uni2ansi(uni, ansi);
 ret = gconvert::uni2utf8(uni, utf8);
 ret = gconvert::utf82ansi(utf8, ansi);
 ret = gconvert::utf82uni(utf8, uni);
 return 0;
}

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