如何使用 wistream 从内存中读取数据，就像从文件中读取数据一样？

发布于 2024-10-05 14:59:56 字数 1039 浏览 7 评论 0原文

在我的上一篇我问的问题是如何像从文件中一样从内存中读取数据。因为我的整个文件都在内存中，所以我想以类似的方式读取它。

我发现回答我的问题，但实际上我需要将行读取为wstring。对于文件，我可以这样做：

wifstream file;
wstring line2;

file.open("C:\\Users\\Mariusz\\Desktop\\zasoby.txt");
if(file.is_open())
{
    while(file.good())
    {
        getline(file,line2);
        wcout << line2 << endl;
    }
}   
file.close();

即使文件是 ASCII 格式的。

现在，我只需使用这个答案。但是，我认为如果有一种方法可以像 wistream 一样处理这块内存，那么将这些行视为 wstring 会是一个更快的解决方案。我需要这个速度很快。

那么有人知道如何将这块内存视为wistream吗？

原文

In my previous question I asked how to read from a memory just as from a file. Because my whole file was in memory I wanted to read it similarly.

I found answer to my question but actually I need to read lines as a wstring. With file I can do this:

wifstream file;
wstring line2;

file.open("C:\\Users\\Mariusz\\Desktop\\zasoby.txt");
if(file.is_open())
{
    while(file.good())
    {
        getline(file,line2);
        wcout << line2 << endl;
    }
}   
file.close();

Even if the file is in ASCII.

Right now I'm simply changing my string line to wstring with a function from this answer. However, I think if there is a way to treat this chunk of memory just like a wistream it would be a faster solution to get this lines as wstrings. And I need this to be fast.

So anybody know how to treat this chunk of memory as a wistream?

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乄_柒ぐ汐 2024-10-12 14:59:56

我假设您的数据已经转换为所需的编码（请参阅@detunized 答案）。

使用我的回答你之前的问题转换是直接的：

namespace io = boost::iostreams;

io::filtering_wistream in;
in.push(warray_source(array, arraySize));

如果你坚持不使用 boost 然后转换如下（仍然简单）：

class membuf : public wstreambuf // <- !!!HERE!!!
{
public:
    membuf(wchar_t* p, size_t n) { // <- !!!HERE!!!
        setg(p, p, p + n);
    }
};

int main()
{
    wchar_t buffer[] = L"Hello World!\nThis is next line\nThe last line";  
    membuf mb(buffer, sizeof(buffer)/sizeof(buffer[0]));

    wistream istr(&mb);
    wstring line;
    while(getline(istr, line))
    {
        wcout << L"line:[" << line << L"]" << endl;
    }
}

另请考虑 this 了解为什么使用纯 char UTF-8 流。

I assume that your data is already converted into the desired encoding (see @detunized answer).

Using my answer to your previous question the conversion is straight forward:

namespace io = boost::iostreams;

io::filtering_wistream in;
in.push(warray_source(array, arraySize));

If you insist on not using boost then the conversion goes as follows (still straight forward):

class membuf : public wstreambuf // <- !!!HERE!!!
{
public:
    membuf(wchar_t* p, size_t n) { // <- !!!HERE!!!
        setg(p, p, p + n);
    }
};

int main()
{
    wchar_t buffer[] = L"Hello World!\nThis is next line\nThe last line";  
    membuf mb(buffer, sizeof(buffer)/sizeof(buffer[0]));

    wistream istr(&mb);
    wstring line;
    while(getline(istr, line))
    {
        wcout << L"line:[" << line << L"]" << endl;
    }
}

Also consider this for why use plain char UTF-8 streams.

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