iostream问题：如何打开unicode文件名。 [英] iostream question: How to open unicode file name.
问题描述
我正在尝试升级使用旧iostream的旧代码。
在代码中的一个地方，我在wchar_t字符串中有一个路径/文件名
（unicode utf-16）。
我需要打开一个ifstream到该文件。但ifstream上的open（）只有
需要char *字符串（mbcs？）。
在旧的iostream中，我可以_wopen（）文件，得到filedesc，并在ifstream上调用
attach（）。
但是标准的iostream中不存在filedescs和attach（）。
我不能将unicode字符串转换为mbcs字符串，因为用户的
默认代码页可能不允许
unicode string。
我当然可以将unicode字符串转换为utf-8，但我找不到任何
方式让iostream open（）相信字符串是utf-8。
尝试ibue（）一个具有自定义代码的自定义语言环境的流
似乎只会影响写入流的数据，而不会影响文件名如何通过
来解释。
有谁知道我怎么能完成打开ifstream到名为
文件的unicode？
为什么ifstream没有wopen（）？
Charles F McDevitt写道：我正在尝试升级一些使用旧iostream的旧代码。
代码中的一个地方，我在wchar_t字符串中有一个路径/文件名
（unicode utf-16）。
我需要打开一个ifstream到该文件。但ifstream上的open（）只需要char *字符串（mbcs？）。
在旧的iostream中，我可以_wopen（）文件，获取filedesc，和
在ifstream上调用attach（）。
但是标准的iostream中不存在filedescs和attach（）。
我不能将unicode字符串转换为mbcs字符串，因为
用户的默认代码页可能不允许
在unicode字符串中的所有字符。
我当然可以将unicode字符串转换为utf-8 ，但我无法找到
任何方式让iostream打开（）相信字符串是
utf-8。
尝试ibue（）一个流使用自定义区域设置有一个自定义的codecvt似乎只影响写入流的数据，而不是如何解释传递给open的文件名称。
有谁知道我是怎么做的可以完成打开一个ifstream到一个名为unicode的文件吗？
为什么ifstream都没有wopen（）？
因为C ++社区不能就这样的函数如何工作达成一致。
对于具有Unicode文件系统的Windows系统，所需的
行为似乎很明显：只需将字符串传递给文件系统即可。但是，自从
C ++试图解决更广泛的系统，其中许多系统不支持unicode文件系统，我们留下了C ++标准哪个
没有标准兼容，可以通过unicode文件打开文件的便携方式
名称。
库实现随VC提供的确提供了一种方法，但是，b $ b。使用C运行时库_wfopen打开文件，然后通过传递_wfopen（）返回到ifstream
构造函数的FILE *来创建
ifstream。
#include< fstream>
void foo（const wchar_t * pwsz）
{
std :: ifstream stm（_wfopen（pwsz，L" rb"））;
//用流做的东西
}
-cd
" Carl Daniel [VC ++ MVP]" < CP ****** @ nospam.mvps.org>在消息中写道
新闻：％2 **************** @ TK2MSFTNGP09.phx.gbl ...Charles F McDevitt写道：我正在尝试升级一些使用旧iostream的旧代码。
在代码的一个地方，我在wchar_t中有一个路径/文件名string
（unicode utf-16）。
我需要打开一个ifstream到该文件。但ifstream上的open（）只需要char *字符串（mbcs？）。
在旧的iostream中，我可以_wopen（）文件，获取filedesc，和
在ifstream上调用attach（）。
但是标准的iostream中不存在filedescs和attach（）。
我不能将unicode字符串转换为mbcs字符串，因为
用户的默认代码页可能不允许
在unicode字符串中的所有字符。
我当然可以将unicode字符串转换为utf-8 ，但我无法找到
任何方式让iostream打开（）相信字符串是
utf-8。
尝试ibue（）一个流使用自定义区域设置有一个自定义的codecvt似乎只影响写入流的数据，而不是如何解释传递给open的文件名称。
有谁知道我是怎么做的可以完成打开ifstream到一个名为unicode的文件吗？
为什么ifstream都没有wopen（）？
因为C + +社区不能就这样的功能如何工作达成一致。
对于具有Unicode文件系统的Windows系统，所需的行为似乎很明显：只需将字符串传递给文件系统即可。但是
因为C ++试图解决范围更广的系统，其中许多系统都不支持unicode文件系统，我们留下了C ++标准。给定一个unicode文件名称的
是没有标准兼容，可移植的方式打开文件。
VC提供的库实现确实提供了一种方法，<但是。使用C运行时库_wfopen打开文件，然后通过传递_wfopen（）返回到ifstream
构造函数的FILE *来创建
ifstream。
#include< fstream> ;
void foo（const wchar_t * pwsz）
{
std :: ifstream stm（_wfopen（pwsz，L" rb"））;
//用流做的东西
}
谢谢..我想那个'这是我唯一的选择。
" Carl Daniel [VC ++ MVP]" < CP ****** @ nospam.mvps.org>写道：[...]为什么ifstream没有wopen（）？
因为C ++社区不能就如何这样的功能应该可行。
对于具有Unicode文件系统的Windows系统，所需的行为似乎很明显：只需将字符串传递给文件系统即可。但是，由于C ++试图解决范围更广的系统，其中许多系统不支持unicode文件系统，我们留下了一个C ++标准，其中
不是给定unicode文件名称的标准兼容，可移植方式打开文件。
我认为这是一个弱论点。毕竟，
C ++也试图解决那些根本没有文件系统的系统。
（Carl，我认识你不是那个与
争论的人。但是，我只是不能让那个
通过未注释。< g>）
[...]
-cd
Schobi
-
Sp******@gmx.de 永远不会被阅读
我是Schobi at suespammers org
为什么我现在应该知道更好/什么时候我不够老？
Beth Orton
I''m trying to upgrade some old code that used old iostreams.
At one place in the code, I have a path/filename in a wchar_t string
(unicode utf-16).
I need to open an ifstream to that file. But the open() on ifstream only
takes char * strings (mbcs?).
In old iostreams, I could _wopen() the file, get the filedesc, and call
attach() on the ifstream.
But filedescs and attach() don''t exist in standard iostreams.
I can''t just convert the unicode string to a mbcs string, because the user''s
default codepage might not allow for all the characters that are in the
unicode string.
I can of course convert the unicode string to utf-8, but I can''t find any
way to get the iostream open() to believe that the string is utf-8.
trying to ibue() a stream with a custom locale that has a custom codecvt
seems to only affect data written to the stream, not how file names passed
to open are interpreted.
Does anyone know how I can accomplish opening an ifstream to a unicode named
file?
Why doesn''t ifstream have a wopen() ?
解决方案Charles F McDevitt wrote:I''m trying to upgrade some old code that used old iostreams.
At one place in the code, I have a path/filename in a wchar_t string
(unicode utf-16).
I need to open an ifstream to that file. But the open() on ifstream
only takes char * strings (mbcs?).
In old iostreams, I could _wopen() the file, get the filedesc, and
call attach() on the ifstream.
But filedescs and attach() don''t exist in standard iostreams.
I can''t just convert the unicode string to a mbcs string, because the
user''s default codepage might not allow for all the characters that
are in the unicode string.
I can of course convert the unicode string to utf-8, but I can''t find
any way to get the iostream open() to believe that the string is
utf-8.
trying to ibue() a stream with a custom locale that has a custom
codecvt seems to only affect data written to the stream, not how file
names passed to open are interpreted.
Does anyone know how I can accomplish opening an ifstream to a
unicode named file?
Why doesn''t ifstream have a wopen() ?
Because the C++ community can''t agree on how such a function should work.
For a system such as Windows that has a Unicode file system, the desired
behavior seems obvious: just pass the string to the filesystem. But since
C++ tries to address a much wider range of systems, many of which don''t
support unicode filesystems, we''re left with a C++ standard in which there
is no standard compliant, portable way to open a file given a unicode file
name.
The library implementation supplied with VC does provide a way to do it,
however. Open the file using the C runtime library _wfopen, then create the
ifstream by passing the FILE* that _wfopen() returns to the ifstream
constructor.
#include <fstream>
void foo(const wchar_t* pwsz)
{
std::ifstream stm(_wfopen(pwsz,L"rb"));
// Do stuff with the stream
}
-cd
"Carl Daniel [VC++ MVP]" <cp******@nospam.mvps.org> wrote in message
news:%2****************@TK2MSFTNGP09.phx.gbl...Charles F McDevitt wrote:I''m trying to upgrade some old code that used old iostreams.
At one place in the code, I have a path/filename in a wchar_t string
(unicode utf-16).
I need to open an ifstream to that file. But the open() on ifstream
only takes char * strings (mbcs?).
In old iostreams, I could _wopen() the file, get the filedesc, and
call attach() on the ifstream.
But filedescs and attach() don''t exist in standard iostreams.
I can''t just convert the unicode string to a mbcs string, because the
user''s default codepage might not allow for all the characters that
are in the unicode string.
I can of course convert the unicode string to utf-8, but I can''t find
any way to get the iostream open() to believe that the string is
utf-8.
trying to ibue() a stream with a custom locale that has a custom
codecvt seems to only affect data written to the stream, not how file
names passed to open are interpreted.
Does anyone know how I can accomplish opening an ifstream to a
unicode named file?
Why doesn''t ifstream have a wopen() ?
Because the C++ community can''t agree on how such a function should work.
For a system such as Windows that has a Unicode file system, the desired
behavior seems obvious: just pass the string to the filesystem. But
since C++ tries to address a much wider range of systems, many of which don''t
support unicode filesystems, we''re left with a C++ standard in which there
is no standard compliant, portable way to open a file given a unicode file
name.
The library implementation supplied with VC does provide a way to do it,
however. Open the file using the C runtime library _wfopen, then create the ifstream by passing the FILE* that _wfopen() returns to the ifstream
constructor.
#include <fstream>
void foo(const wchar_t* pwsz)
{
std::ifstream stm(_wfopen(pwsz,L"rb"));
// Do stuff with the stream
}
-cd
Thanks.. I guess that''s my only choice.
"Carl Daniel [VC++ MVP]" <cp******@nospam.mvps.org> wrote:[...]Why doesn''t ifstream have a wopen() ?
Because the C++ community can''t agree on how such a function should work.
For a system such as Windows that has a Unicode file system, the desired
behavior seems obvious: just pass the string to the filesystem. But since
C++ tries to address a much wider range of systems, many of which don''t
support unicode filesystems, we''re left with a C++ standard in which there
is no standard compliant, portable way to open a file given a unicode file
name.
I consider that a weak argument. After all,
C++ also tries to address systems where there''s
no file system at all.
(Carl, I know you''re not the one to argue with
about that. However, I just couldn''t let that
pass uncommented. <g>)
[...]
-cd
Schobi
--
Sp******@gmx.de is never read
I''m Schobi at suespammers org
"And why should I know better by now/When I''m old enough not to?"
Beth Orton
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