我正嘗試在二進制模式下寫入帶有ofstream的wstring文件，但我認爲我做錯了什麼。這是我已經試過：在例如火狐以二進制模式將utf16寫入文件
ofstream outFile("test.txt", std::ios::out | std::ios::binary);
wstring hello = L"hello";
outFile.write((char *) hello.c_str(), hello.length() * sizeof(wchar_t));
outFile.close();
開幕的test.txt與編碼設置爲UTF-16，它會顯示爲：
你好
有誰能告訴我爲什麼會發生這種情況？
編輯：
打開文件中的十六進制編輯器，我得到：
FF FE 68 00 00 00 65 00 00 00 6C 00 00 00 6C 00 00 00 6F 00 00 00
看起來像我的每個人物出於某種原因之間得到兩個額外的字節？
我懷疑sizeof（wchar_t）在你的環境中是4，即它寫出UTF-32/UCS-4而不是UTF-16。這當然是十六進制轉儲的樣子。
這很容易測試（只是打印出sizeof（wchar_t）），但我很確定這是怎麼回事。
要從UTF-32 wstring轉換爲UTF-16，您需要應用正確的編碼，因爲代理對會發揮作用。
是的，你是正確的wchar_t的大小爲4，我在mac。因此，這解釋了很多:)我知道UTF-16中的代理對，將不得不進一步研究。 – Cactuar 2008-10-16 08:01:10
從輸出中你不能告訴它它是UTF-16或UTF-32，它顯示的只是wchar_t是4個字節寬。字符串的編碼不是由語言定義的（儘管它最可能是UCS-4）。 – 2008-10-16 13:10:30
您應該在十六進制編輯器（如WinHex）中查看輸出文件，以便查看實際位和字節，以驗證輸出實際上是UTF-16。張貼在這裏，讓我們知道結果。這將告訴我們是否應該責怪Firefox或您的C++程序。
但是在我看來，像您的C++程序一樣工作，Firefox並沒有正確解釋您的UTF-16。 UTF-16爲每個字符調用兩個字節。但Firefox是印刷兩倍多的字符，因爲它應該，所以它可能是試圖解釋你的字符串爲UTF-8或ASCII，一般只需要每個字符1個字節。
當你說「Firefox編碼設置爲UTF16」你是什麼意思？我懷疑這項工作是否奏效。
在這裏，我們遇到了很少使用的區域設置屬性。 如果你的輸出字符串作爲一個字符串（而不是原始數據），你可以得到的語言環境做適當的轉換自動神奇。
N.B.此代碼沒有考慮到wchar_t的字符的帳戶edianness。
#include <locale>
#include <fstream>
#include <iostream>
// See Below for the facet
#include "UTF16Facet.h"
int main(int argc,char* argv[])
{
// construct a custom unicode facet and add it to a local.
UTF16Facet *unicodeFacet = new UTF16Facet();
const std::locale unicodeLocale(std::cout.getloc(), unicodeFacet);
// Create a stream and imbue it with the facet
std::wofstream saveFile;
saveFile.imbue(unicodeLocale);
// Now the stream is imbued we can open it.
// NB If you open the file stream first. Any attempt to imbue it with a local will silently fail.
saveFile.open("output.uni");
saveFile << L"This is my Data\n";
return(0);
}
該文件：UTF16Facet.h
#include <locale>
class UTF16Facet: public std::codecvt<wchar_t,char,std::char_traits<wchar_t>::state_type>
{
typedef std::codecvt<wchar_t,char,std::char_traits<wchar_t>::state_type> MyType;
typedef MyType::state_type state_type;
typedef MyType::result result;
/* This function deals with converting data from the input stream into the internal stream.*/
/*
* from, from_end: Points to the beginning and end of the input that we are converting 'from'.
* to, to_limit: Points to where we are writing the conversion 'to'
* from_next: When the function exits this should have been updated to point at the next location
* to read from. (ie the first unconverted input character)
* to_next: When the function exits this should have been updated to point at the next location
* to write to.
*
* status: This indicates the status of the conversion.
* possible values are:
* error: An error occurred the bad file bit will be set.
* ok: Everything went to plan
* partial: Not enough input data was supplied to complete any conversion.
* nonconv: no conversion was done.
*/
virtual result do_in(state_type &s,
const char *from,const char *from_end,const char* &from_next,
wchar_t *to, wchar_t *to_limit,wchar_t* &to_next) const
{
// Loop over both the input and output array/
for(;(from < from_end) && (to < to_limit);from += 2,++to)
{
/*Input the Data*/
/* As the input 16 bits may not fill the wchar_t object
* Initialise it so that zero out all its bit's. This
* is important on systems with 32bit wchar_t objects.
*/
(*to) = L'\0';
/* Next read the data from the input stream into
* wchar_t object. Remember that we need to copy
* into the bottom 16 bits no matter what size the
* the wchar_t object is.
*/
reinterpret_cast<char*>(to)[0] = from[0];
reinterpret_cast<char*>(to)[1] = from[1];
}
from_next = from;
to_next = to;
return((from > from_end)?partial:ok);
}
/* This function deals with converting data from the internal stream to a C/C++ file stream.*/
/*
* from, from_end: Points to the beginning and end of the input that we are converting 'from'.
* to, to_limit: Points to where we are writing the conversion 'to'
* from_next: When the function exits this should have been updated to point at the next location
* to read from. (ie the first unconverted input character)
* to_next: When the function exits this should have been updated to point at the next location
* to write to.
*
* status: This indicates the status of the conversion.
* possible values are:
* error: An error occurred the bad file bit will be set.
* ok: Everything went to plan
* partial: Not enough input data was supplied to complete any conversion.
* nonconv: no conversion was done.
*/
virtual result do_out(state_type &state,
const wchar_t *from, const wchar_t *from_end, const wchar_t* &from_next,
char *to, char *to_limit, char* &to_next) const
{
for(;(from < from_end) && (to < to_limit);++from,to += 2)
{
/* Output the Data */
/* NB I am assuming the characters are encoded as UTF-16.
* This means they are 16 bits inside a wchar_t object.
* As the size of wchar_t varies between platforms I need
* to take this into consideration and only take the bottom
* 16 bits of each wchar_t object.
*/
to[0] = reinterpret_cast<const char*>(from)[0];
to[1] = reinterpret_cast<const char*>(from)[1];
}
from_next = from;
to_next = to;
return((to > to_limit)?partial:ok);
}
};
請注意，您的Facet實現到UCS-2而不是UTF-16的轉換。 UTF-16是一種可變長度編碼，稱爲代理對的儀器。 UCS-2是Unicode的一個子集，這就是UTF-16發明的原因。 – 2017-05-04 21:12:29
在使用wofstream和監守的wofstream轉換用值0A到2個字節0D 0A所有字節以上定義的UTF16面失敗窗口，這是不考慮你如何傳遞， '\ X0A' 的0A字節，L '\ X0A'，L '\ x000A'， '\ n'，L '\ n' 和std :: ENDL都給予同樣的結果。 在Windows下你必須打開該文件以二進制方式使用ofstream（不是wofsteam）和寫輸出，就像它是在原崗位完成。
提供的Utf16Facet沒有在大字符串gcc中工作，這裏是我工作的版本...這種方式的文件將被保存在UTF-16LE。對於UTF-16BE，只需將do_in和do_out中的分配顛倒過來即可。 to[0] = from[1]和to[1] = from[0]
#include <locale>
#include <bits/codecvt.h>
class UTF16Facet: public std::codecvt<wchar_t,char,std::char_traits<wchar_t>::state_type>
{
typedef std::codecvt<wchar_t,char,std::char_traits<wchar_t>::state_type> MyType;
typedef MyType::state_type state_type;
typedef MyType::result result;
/* This function deals with converting data from the input stream into the internal stream.*/
/*
* from, from_end: Points to the beginning and end of the input that we are converting 'from'.
* to, to_limit: Points to where we are writing the conversion 'to'
* from_next: When the function exits this should have been updated to point at the next location
* to read from. (ie the first unconverted input character)
* to_next: When the function exits this should have been updated to point at the next location
* to write to.
*
* status: This indicates the status of the conversion.
* possible values are:
* error: An error occurred the bad file bit will be set.
* ok: Everything went to plan
* partial: Not enough input data was supplied to complete any conversion.
* nonconv: no conversion was done.
*/
virtual result do_in(state_type &s,
const char *from,const char *from_end,const char* &from_next,
wchar_t *to, wchar_t *to_limit,wchar_t* &to_next) const
{
for(;from < from_end;from += 2,++to)
{
if(to<=to_limit){
(*to) = L'\0';
reinterpret_cast<char*>(to)[0] = from[0];
reinterpret_cast<char*>(to)[1] = from[1];
from_next = from;
to_next = to;
}
}
return((to != to_limit)?partial:ok);
}
/* This function deals with converting data from the internal stream to a C/C++ file stream.*/
/*
* from, from_end: Points to the beginning and end of the input that we are converting 'from'.
* to, to_limit: Points to where we are writing the conversion 'to'
* from_next: When the function exits this should have been updated to point at the next location
* to read from. (ie the first unconverted input character)
* to_next: When the function exits this should have been updated to point at the next location
* to write to.
*
* status: This indicates the status of the conversion.
* possible values are:
* error: An error occurred the bad file bit will be set.
* ok: Everything went to plan
* partial: Not enough input data was supplied to complete any conversion.
* nonconv: no conversion was done.
*/
virtual result do_out(state_type &state,
const wchar_t *from, const wchar_t *from_end, const wchar_t* &from_next,
char *to, char *to_limit, char* &to_next) const
{
for(;(from < from_end);++from, to += 2)
{
if(to <= to_limit){
to[0] = reinterpret_cast<const char*>(from)[0];
to[1] = reinterpret_cast<const char*>(from)[1];
from_next = from;
to_next = to;
}
}
return((to != to_limit)?partial:ok);
}
};
如果使用C++11標準（因爲有很多附加的包括像"utf8"它永遠解決了這個問題），這是很容易。
但是，如果你想使用多平臺的代碼與舊標準，您可以使用此方法與流寫：
stxutif.h到項目上面以ANSI模式打開文件，並將BOM添加到文件的開頭，如下所示：
std::ofstream fs;
fs.open(filepath, std::ios::out|std::ios::binary);
unsigned char smarker[3];
smarker[0] = 0xEF;
smarker[1] = 0xBB;
smarker[2] = 0xBF;
fs << smarker;
fs.close();
然後打開該文件作爲UTF還有寫你的內容：
std::wofstream fs;
fs.open(filepath, std::ios::out|std::ios::app);
std::locale utf8_locale(std::locale(), new utf8cvt<false>);
fs.imbue(utf8_locale);
fs << .. // Write anything you want...
添加方面與流從wchar_t的做轉換到正確的輸出相關的地方。見下文。 – 2008-10-16 13:01:42