How do we write that in C++?<\/p>\n
At a first glance, you could be tempted to write it like this:<\/p>\n
#include < fstream >\r\n\r\nint main()\r\n{\r\n\tstd::ofstream testFile;\r\n\r\n\ttestFile.open(\"demo.xml\", std::ios::out | std::ios::binary); \r\n\r\n\tstd::string text =\r\n\t\t\"< ?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"? >\\n\"\r\n\t\t\"< root description=\\\"this is a na\u00efve example\\\" >\\n< \/root >\";\r\n\r\n\ttestFile << text;\r\n\r\n\ttestFile.close();\r\n\r\n\treturn 0;\r\n}\r\n<\/pre>\nWhen you open the file in IE for instance, surprize! It’s not rendered correctly:<\/p>\n
![\"\"](\"\/blog\/wp-content\/uploads\/2008\/10\/ieutf8_1.png\")
<\/p>\n
So you could be tempted to say “let’s switch to wstring and wofstream”.<\/p>\n
\r\nint main()\r\n{\r\n\tstd::wofstream testFile;\r\n\r\n\ttestFile.open(\"demo.xml\", std::ios::out | std::ios::binary); \r\n\r\n\tstd::wstring text = \r\n\t\tL\"< ?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"? >\\n\"\r\n\t\tL\"< root description=\\\"this is a na\u00efve example\\\" >\\n< \/root >\";\r\n\r\n\ttestFile << text;\r\n\r\n\ttestFile.close();\r\n\r\n\treturn 0;\r\n}\r\n<\/pre>\nAnd when you run it and open the file again, no change. So, where is the problem? Well, the problem is that neither ofstream nor wofstream write the text in a UTF-8 format. If you want the file to really be in UTF-8 format, you have to encode the output buffer in UTF-8. And to do that we can use WideCharToMultiByte(). This Windows API maps a wide character string to a new character string (which is not necessary from a multibyte character set). The first argument indicates the code page. For UTF-8 we need to specify CP_UTF8.<\/p>\n
The following helper functions encode a std::wstring into a UTF-8 stream, wrapped into a std::string.<\/p>\n
#include < windows.h >\r\n\r\nstd::string to_utf8(const wchar_t* buffer, int len)\r\n{\r\n\tint nChars = ::WideCharToMultiByte(\r\n\t\tCP_UTF8,\r\n\t\t0,\r\n\t\tbuffer,\r\n\t\tlen,\r\n\t\tNULL,\r\n\t\t0,\r\n\t\tNULL,\r\n\t\tNULL);\r\n\tif (nChars == 0) return \"\";\r\n\r\n\tstring newbuffer;\r\n\tnewbuffer.resize(nChars) ;\r\n\t::WideCharToMultiByte(\r\n\t\tCP_UTF8,\r\n\t\t0,\r\n\t\tbuffer,\r\n\t\tlen,\r\n\t\tconst_cast< char* >(newbuffer.c_str()),\r\n\t\tnChars,\r\n\t\tNULL,\r\n\t\tNULL); \r\n\r\n\treturn newbuffer;\r\n}\r\n\r\nstd::string to_utf8(const std::wstring& str)\r\n{\r\n\treturn to_utf8(str.c_str(), (int)str.size());\r\n}\r\n<\/pre>\nWith that in hand, all you have to do is doing the following changes:<\/p>\n
int main()\r\n{\r\n\tstd::ofstream testFile;\r\n\r\n\ttestFile.open(\"demo.xml\", std::ios::out | std::ios::binary); \r\n\r\n\tstd::wstring text =\r\n\t\tL\"< ?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"? >\\n\"\r\n\t\tL\"< root description=\\\"this is a na\u00efve example\\\" >\\n< \/root >\";\r\n\r\n\tstd::string outtext = to_utf8(text);\r\n\r\n\ttestFile << outtext;\r\n\r\n\ttestFile.close();\r\n\r\n\treturn 0;\r\n}\r\n<\/pre>\nAnd now when you open the file, you get what you wanted in the first place.<\/p>\n
![\"\"](\"\/blog\/wp-content\/uploads\/2008\/10\/ieutf8_2.png\")
<\/p>\n
And that is all!<\/p>\n","protected":false},"excerpt":{"rendered":"
Let’s say you need to write an XML file with this content: < ?xml version=”1.0″ encoding=”UTF-8″? > < root description=”this is a na\u00efve example” > < \/root > How do we write that in C++? At a first glance, you could be tempted to write it like this: #include < fstream > int main() { … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_uag_custom_page_level_css":"","advgb_blocks_editor_width":"","advgb_blocks_columns_visual_guide":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[7],"tags":[],"class_list":["post-135","post","type-post","status-publish","format-standard","hentry","category-c"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t