Question

我试图使用这种迭代器，但是我有以下代码的错误：

void linearMatrix::Write_File_Matrix(const char *Path)
{
    ofstream FILE(Path, std::ios::out | std::ofstream::binary);
    FILE.write(reinterpret_cast<const char *>(&myWidth), sizeof(float));
    FILE.write(reinterpret_cast<const char *>(&myHeight), sizeof(float));
    ostreambuf_iterator<float> out_it (FILE);
    copy(myVector.begin(), myVector.end(), out_it);
}

void linearMatrix::Read_File_Matrix(const char *Path)
{
    ifstream FILE(Path, std::ios::in | std::ifstream::binary);

    if(!FILE)
    {
        cerr << "Cannot open the file" << endl;
        exit(1);
    }
    FILE.read(reinterpret_cast<const char *>(&myWidth), sizeof(myWidth));
    FILE.read(reinterpret_cast<const char *>(&myHeight), sizeof(myHeight));
    istreambuf_iterator<float> iter(FILE);
    copy(iter.begin(), iter.end(), std::back_inserter(myVector));
}

问题是：

1- ostreambuf_iterator<float> out_it (FILE);

错误：从'void *'无效转换为 'std :: ostreambuf_iterator :: streambuf_type * {aka std :: basic_streambuf＆gt; *}' [-fpermissive]

2- FILE.read(reinterpret_cast<const char *>(&myWidth), sizeof(myWidth));

错误：从'const char *'无效转换为'std :: basic_istream :: char_type * {aka char *}'[-fpermissive]

3- FILE.read(reinterpret_cast<const char *>(&myHeight), sizeof(myHeight));

错误：从'const char *'无效转换为 'std :: basic_istream :: char_type * {aka char *}'[-fpermissive]

4- std::ifstream FILE(Path, std::ios::in | std::ifstream::binary);

错误：从'void *'无效转换为 'std :: ostreambuf_iterator :: streambuf_type * {aka std :: basic_streambuf＆gt; *}' [-fpermissive]

5- copy（iter.begin（），iter.end（），std :: back_inserter（myVector））;

错误：'class std :: istreambuf_iterator'没有名为的成员   “开始”

错误：'class std :: istreambuf_iterator'没有名为的成员   “结束”

我做错了什么？我正在使用来自CUDA的nsight eclipse，但是使用g ++编译C ++项目。我指的是：Reading and writing a std::vector into a file correctly

#include <iostream>
#include <algorithm>
#include <iterator>
#include <fstream>
#include <vector>

using namespace std;

void Write_File_Matrix(const char *Path)
{
    float myWidth = 0;
    float myHeight = 0;
    vector<float> v;
    v[0] = 1;
    v[1] = 2;
    v[2] = 3;
    ofstream outFILE(Path, ios::out | ofstream::binary);
    outFILE.write(reinterpret_cast<const char *>(&myWidth), sizeof(float));
    outFILE.write(reinterpret_cast<const char *>(&myHeight), sizeof(float));
    ostreambuf_iterator<float> out_it (outFILE);
    copy(V.begin(), V.end(), out_it);
}

void Read_File_Matrix(const char *Path)
{
    float myWidth = 0;
    float myHeight = 0;
    vector<float> v;

    ifstream inFILE(Path, ios::in | ifstream::binary);

    if(!inFILE)
    {
        cerr << "Cannot open the file" << endl;
        exit(1);
    }
    inFILE.read(reinterpret_cast<const char *>(&myWidth), sizeof(myWidth));
    inFILE.read(reinterpret_cast<const char *>(&myHeight), sizeof(myHeight));
    istreambuf_iterator<float> iter(inFILE);
    copy(iter.begin(), iter.end(), std::back_inserter(myVector));
}

int main() {

    Write_File_Matrix("M.dat");
    Read_File_Matrix("R.dat");

    return 0;
}

Answer 1

编辑：删除了对1,4的错误答案。

回复：2,3。你无法读入const char*;它是 const 。转而使用char*。这就是错误信息所说的内容。

Re：5。是的，迭代器没有begin()和end()成员函数。你已经有了一个文件开头的迭代器（一旦解决了以前的问题）。它的名字是iter。现在您需要一个文件结束迭代器，正确的调用是std::copy(iter, end_iter, std::back_inserter(myVector));。

Answer 2

1- ostreambuf_iterator out_it（FILE）;

错误：无效转换为'void *'到'std :: ostreambuf_iterator :: streambuf_type * {aka std :: basic_streambuf＆gt; *}'[-fpermissive]

std::ostreambuf_iterator将流的字符类型作为模板参数，而不是您要转换为的类型。尝试：

std::ostreambuf_iterator<char> out_it(FILE);

同样＃4。

编辑：让我们解决您的大问题，而不是小问题：

不要为迭代器而烦恼，只需一次性写出矢量数据：

void Write_File_Matrix(const char *Path)
{
    float myWidth = 0;
    float myHeight = 0;
    vector<float> v;
    v[0] = 1;
    v[1] = 2;
    v[2] = 3;
    ofstream outFILE(Path, ios::out | ofstream::binary);
    outFILE.write(reinterpret_cast<const char *>(&myWidth), sizeof(float));
    outFILE.write(reinterpret_cast<const char *>(&myHeight), sizeof(float));
    outFile.write(reinterpret_cast<const char *>(&v[0]), v.size()*sizeof(float));
}

然而，阅读仍然需要一次一件。

void Read_File_Matrix(const char *Path)
{
    float myWidth = 0;
    float myHeight = 0;
    vector<float> v;

    ifstream inFILE(Path, ios::in | ifstream::binary);

    if(!inFILE)
    {
        cerr << "Cannot open the file" << endl;
        exit(1);
    }
    inFILE.read(reinterpret_cast<char *>(&myWidth), sizeof(myWidth));
    inFILE.read(reinterpret_cast<char *>(&myHeight), sizeof(myHeight));
    float f;
    while( inFILE.read(reinterpret_cast<char *>(&f), sizeof(f)))
      v.push_back(f);
}

读取二进制文件并正确使用流迭代器

2 个答案: