c++ - 将 ifstream 读取为 char* 以进行 int 和 string 转换

Question

我在解析具有以下内容的二进制数据文件时遇到了一些麻烦，该文件读取了第一行

int LineLength = 300;
int Offset= 4586;
ifstream ifn("BinaryFile.bin");
char* line = new char[LineLength];
ifn.seekg(Offset);
while (ifn.good())
{
    ifn.read(line, LineLength);
}   
for (int i = 0; i < LineLength; i++)
    printf("%02X ", line[i]);

这是打印出来的：

00 FFFFFFDD 01 00 00 22 FFFFFFB0 01 00 03 4F 50 2D 31 01 31 32 33 

当我使用十六进制编辑器查看原始数据时，它看起来像这样：

00 55 24 00 00 F4 BC 01 00 03 4F 50 2D 31 01 31 32 33

我真的不希望它改变数据，我需要将一些字节转换为整数，一些转换为字符串，还有一些最终会变成日期，但我遇到了一些真正的挑战。

string* DataType= new string[3]{ "int","int","string" };
int*  StartingPosition =new int[3] { 1,10,11 };
int*  ColumnWidth =new int[3] { 4,1,25 };       
char* locale = setlocale(LC_ALL, "UTF-8");

for (string Name : DataType) {
    std::vector<char> CurrentColumnBytes(ColumnWidth);
    for (int C = StartingPosition; C < ColumnWidth + StartingPosition; ++C)
    {
        int Index = C - StartingPosition;       
        CurrentColumnBytes[Index] = line[C];
    }
    if (DataType == "int") {
        // still working out how to get a little endian result from 2-4 bytes if I use char
        // since it is combining bytes as shown above
    }
    if (DataType == "string") {
        for (std::vector<char>::const_iterator i = CurrentColumnBytes.begin(); i != CurrentColumnBytes.end(); ++i)
            std::cout << *i;
    }
}

我尝试使用wchar_tandwint_t而不是char作为类型。我wint_t能够将多个字节转换为一个小字节序 int，但是我似乎无法从中得到一个字符串。

对于它的价值，我还尝试使用以下方法来获取整数，但不能获取字符串。

int LineLength = 300;
int counter = 0;
wchar_t* line = new wchar_t[LineLength];
while ((c = fgetwc("BinaryFile.bin")) != WEOF) {
    line[counter] = c;
    counter++;
    if (counter > LineLength - 1) {
        break;
    }
}

标签： c++parsingbinaryfiles

Answer 1

好的，所以问题是您需要将文件读入unsigned char vector/数组。也不要使用fgetwc，否则你只会得到每隔一个字节，并且它会检测一行中何时有多个空字节并将它们组合起来，这可能会影响你的计数。Ifstream似乎没有一种简单的方法可以将文件的一部分读入unsigned char vector

int LineLength = 300;
int counter = 0;
std::vector<unsigned char> line(LineLength);
while ((c = fgetw("BinaryFile.bin")) != WEOF) {
    line[counter] = static_cast<unsigned char>(c);
    counter++;
    if (counter > LineLength - 1) {
        break;
    }
}

然后，一旦将其放入向量中，就可以单独处理数据

for (string Name : DataType) { // here just looping over the columns that were defined in the JSON file - excluding some things that aren't relevant
{
    char* locale = setlocale(LC_ALL, "UTF-8");
    std::vector<unsigned char> CurrentColumnBytes(ColumnWidth);     
    for (int C = StartingPosition; C < ColumnWidth + StartingPosition; ++C)
    {
        int Index = C - StartingPosition;       
        CurrentColumnBytes[Index] = BufferedLine[C];
    }
    if (DataType == "int") {    
        cout << DataParser::LEByte(CurrentColumnBytes); //custom function that tests length, converts to Little Endian int from the individual bytes.
    }
    if (DataType == "string") {
        for (int i = 0; i < ColumnWidth; i++)
            cout<<CurrentColumnBytes[i];
    }
    cout<<" | ";    
}