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std::wstring (from ifstream)

hansaaa (115)
Hi, I have a code, that gives following error:

Error	1	error C2440: '<function-style-cast>' : cannot convert from 'std::ifstream' to 'std::istreambuf_iterator<_Elem,_Traits>'	e:\rental-pc-c\users\a\documents\visual studio 2012\projects\implementations\footy - get odds, right to db\windowsapplicationa\windowsapplicationa\windowsapplicationa.cpp	408	1	WindowsApplicationA


Code is:
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ifstream *inFile = new ifstream(szFile);
	std::wstring szwFileStr((std::istreambuf_iterator<wchar_t>(*inFile)),std::istreambuf_iterator<wchar_t>());


It fails,on the bold part
Need the string, containing the input from the file, to be a std::wstring (needs to handle somce chars, not handled by std::string).

How can I "fix" this?

Regards,

C
Last edited on
naraku9333 (2163)
I think you need to pass the rdbuf to the stream buffer 
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std::ifstream inFile(szFile);
std::wstring szwFileStr((std::istreambuf_iterator<wchar_t>(inFile.rdbuf())),std::istreambuf_iterator<wchar_t>());
hansaaa (115)
Unfortunately, no. That, gives an error, too:

Error	1	error C2440: '<function-style-cast>' : cannot convert from 'std::basic_filebuf<_Elem,_Traits> *' to 'std::istreambuf_iterator<_Elem,_Traits>'	e:\rental-pc-c\users\a\documents\visual studio 2012\projects\implementations\footy - get odds, right to db\windowsapplicationa\windowsapplicationa\windowsapplicationa.cpp	411	1	WindowsApplicationA


this, works:
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wifstream *inFile = new wifstream(szFile);
	std::wstring szwFileStr((std::istreambuf_iterator<wchar_t>(*inFile)),std::istreambuf_iterator<wchar_t>());


but, special characters, are still not read in correctly.

E.G., the file contains characters, such as ä, and ê, and they turn out as 
ö


I think, the in file, is UTF-8.

Any ideas, some one? :)
Last edited on
tntxtnt (211)
well i got the old utf8.h of helios http://www.cplusplus.com/user/helios/

use the loadContent(const string& filename, wstring& dest) function to load content of filename to dest

utf8.h
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/*
* Copyright (c) 2009, Helios (helios.vmg@gmail.com)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*     * Redistributions of source code must retain the above copyright notice,
*       this list of conditions and the following disclaimer.
*     * Redistributions in binary form must reproduce the above copyright
*       notice, this list of conditions and the following disclaimer in the
*       documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY HELIOS "AS IS" AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL HELIOS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#ifndef HELIOS_UTF8_H
#define HELIOS_UTF8_H


#include <iostream>
#include <fstream>
#include <string>
#include <stdlib.h>
using namespace std;


#define BOM8A 0xEF
#define BOM8B 0xBB
#define BOM8C 0xBF

typedef unsigned char uchar;

/*
string: a UTF-8-encoded C string (nul terminated)
Return value: a wchar_t C string.

The function handles memory allocation on its own.

Limitations: Only handles the range [U+0000;U+FFFF], higher code points are
changed to '?'.

Assumptions: sizeof(wchar_t)>=2
*/
wchar_t *UTF8_to_WChar(const char*);

//Do not call me.
long getUTF8size(const wchar_t*);

/*
string: a wchar_t C string (nul terminated)
Return value: a UTF-8-encoded C string.

The function handles memory allocation on its own.

Limitations: Only handles the range [U+0000;U+FFFF], higher code points are
changed to '?'.

Assumptions: sizeof(wchar_t)>=2
*/
char *WChar_to_UTF8(const wchar_t*);;;;



//my helper function
void loadContent(const string& a, wstring& b);

#endif


utf8.cpp
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/*
* Copyright (c) 2009, Helios (helios.vmg@gmail.com)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*     * Redistributions of source code must retain the above copyright notice,
*       this list of conditions and the following disclaimer.
*     * Redistributions in binary form must reproduce the above copyright
*       notice, this list of conditions and the following disclaimer in the
*       documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY HELIOS "AS IS" AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL HELIOS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "utf8.h"


wchar_t *UTF8_to_WChar(const char *string){
	long b=0,
		c=0;
	if ((uchar)string[0]==BOM8A && (uchar)string[1]==BOM8B && (uchar)string[2]==BOM8C)
		string+=3;
	for (const char *a=string;*a;a++)
		if (((uchar)*a)<128 || (*a&192)==192)
			c++;
	wchar_t *res=new wchar_t[c+1];
	res[c]=0;
	for (uchar *a=(uchar*)string;*a;a++){
		if (!(*a&128))
			//Byte represents an ASCII character. Direct copy will do.
			res[b]=*a;
		else if ((*a&192)==128)
			//Byte is the middle of an encoded character. Ignore.
			continue;
		else if ((*a&224)==192)
			//Byte represents the start of an encoded character in the range
			//U+0080 to U+07FF
			res[b]=((*a&31)<<6)|(a[1]&63);
		else if ((*a&240)==224)
			//Byte represents the start of an encoded character in the range
			//U+07FF to U+FFFF
			res[b]=((*a&15)<<12)|((a[1]&63)<<6)|(a[2]&63);
		else if ((*a&248)==240){
			//Byte represents the start of an encoded character beyond the
			//U+FFFF limit of 16-bit integers
			res[b]='?';
		}
		b++;
	}
	return res;
}

//Do not call me.
long getUTF8size(const wchar_t *string){
	if (!string)
		return 0;
	long res=0;
	for (;*string;string++){
		if (*string<0x80)
			res++;
		else if (*string<0x800)
			res+=2;
		else
			res+=3;
	}
	return res;
}

char *WChar_to_UTF8(const wchar_t *string){
	long fSize=getUTF8size(string);
	char *res=new char[fSize+1];
	res[fSize]=0;
	if (!string)
		return res;
	long b=0;
	for (;*string;string++,b++){
		if (*string<0x80)
			res[b]=(char)*string;
		else if (*string<0x800){
			res[b++]=(*string>>6)|192;
			res[b]=(*string&63)|128;
		}else{
			res[b++]=(*string>>12)|224;
			res[b++]=((*string&4095)>>6)|128;
			res[b]=(*string&63)|128;
		}
	}
	return res;
}


//my helper function
void loadContent(const string& filename, wstring& dest)
{
    ifstream fin(filename.c_str(), ios::binary);
    if(!fin)
    {
        cout<<"Cannot open file\n";
        exit(1);
    }
    fin.seekg(0, ios::end);
    int len = fin.tellg();
    fin.seekg(0, ios::beg);

    char *content = new char[len+1];
    fin.read(content, len);
/**/fin.close();
    content[len] = '\0';

    wchar_t *wcontent = UTF8_to_WChar(content);
    dest = wcontent;
/**/delete [] content;
/**/delete [] wcontent;
}
Cubbi (4774)
Just use std::wifstream instead of std::ifstream, then your istreambuf iterators can be constructed for wchar_t
Duthomhas (13130)
If you use std::wifstream then you have to install a UTF-8 filter on it to make it work anyway. And since no compiler yet supports <codecvt> there's not much point. Just open the file with a std::ifstream, read a line with a std::string, and convert it to a std::wstring using something like helios's stuff (or whatever).
Cubbi (4774)
huh?
you don't need codecvt on systems that support Unicode well (like Linux), just use any suitable locale.
Microsoft's Visual Studio and Clang's libc++ support codecvt since 2010
Last edited on
hansaaa (115)
Hi, I am now using 
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std::wifstream f7wstream(szwM);
std::wstring f7wstr((std::istreambuf_iterator<wchar_t>(f7wstream)), std::istreambuf_iterator<wchar_t>());
, on a UTF-8 encoded xml stream.

Characters such as é, ö, etc, are still not displayed correctly. E.g., "ö", becomes "ö".
This is Visual Studio, 2012, using Unicode Character set.

how can this be/how can I "fix" it?

Thanks!
Last edited on
andywestken (4087)
Either using codecvt, or by using a special flag.

The code was tested with Visual C++ 2010, but should work with later versions, I would hope.

Andy

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#include <iostream>
#include <fstream>
#include <string>
#include <iterator>
#include <locale>
#include <codecvt>
#include <cstdio>  // for _fileno
#include <io.h>    // for _setmode
#include <fcntl.h> // for _O_U16TEXT

std::wstring LoadText1(const wchar_t* filePath);
std::wstring LoadText2(const wchar_t* filePath);

int main ()
{
    _setmode(_fileno(stdout), _O_U16TEXT);

    const wchar_t filePath[] = L"C:\\Test\\test_utf8.txt";

    std::wstring text1 = LoadText1(filePath);
    std::wcout << text1 << std::endl;

    std::wstring text2 = LoadText2(filePath);
    std::wcout << text2 << std::endl;

    return 0;
}

std::wstring LoadText1(const wchar_t* filePath)
{
    std::wstring text;

    FILE* fp = nullptr;
    _wfopen_s(&fp, filePath , L"r, ccs=UTF-8"); // automatically skips BOM
    std::wifstream ifs(fp);

    typedef std::istreambuf_iterator<wchar_t> iter_type;
    iter_type begin(ifs);
    iter_type end;

    text.assign(begin, end);

    fclose(fp);

    return text;
}

std::wstring LoadText2(const wchar_t* filePath)
{
    std::wifstream ifs(filePath);
    ifs.imbue(std::locale(std::locale::empty(), new std::codecvt_utf8<wchar_t>));

    typedef std::istreambuf_iterator<wchar_t> iter_type;
    iter_type begin(ifs);
    iter_type end;

    return std::wstring(++begin, end); // ++ to skip the BOM
}
Last edited on
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