Qt/C++如何定位在文件的中间（偏移）->唯一知道的是文件大小
大家好，在 Qt 中我有：
FILE *pInFile = fopen(strFileName.toLatin1().constData(), "r");
QFileInfo fi(strFileName);
qint64 fileSize = fi.size();
//GO TO THE MIDDLE
//WHAT IS THE POSITION OF THE MIDDLE (INTEGER)
我想知道文件中间的偏移量，而不是在循环中读取整个文件（fgets）。基于该偏移量，我想获得该位置。
基本上;
- 根据给定的字节（例如：fileSize/2）从文件中获取偏移量
- 基于该偏移量的位置是什么（行索引）
是否可以使用类似的东西来确定位置？ int centerPos = ftell(偏移中间, pInFile);
我认为我走的路不对，你能给我一些建议吗？
谢谢
。
并且最好定位在该位置的开头
Hy all, in Qt i have:
FILE *pInFile = fopen(strFileName.toLatin1().constData(), "r");
QFileInfo fi(strFileName);
qint64 fileSize = fi.size();
//GO TO THE MIDDLE
//WHAT IS THE POSITION OF THE MIDDLE (INTEGER)
Instead of reading trough the whole file (fgets) in a loop, i want to know the offset of the middle of the file. And based on that offset i want to get that position.
Basically;
- get offset from a file based on my given bytes (example: fileSize/2)
- based on that offset what is the position (row index)
Is it possible to have something like this for determining position?
int centerPos = ftell(Offset middle, pInFile);
I don't think i'm on the right path here, can u give some advice?
Thx
ps.
And would be nice to position on the the beginning of the position
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使用 QFile 而不是原始文件指针。它有一个
seek方法。http://doc.qt.nokia.com/latest/qfile.html#seek
您可以使用...确定文件的中间位置
，然后，如上所述，在调用后从该位置开始读取
Use
QFileinstead of a raw file pointer. It has aseekmethod.http://doc.qt.nokia.com/latest/qfile.html#seek
You can determine the middle of the file using
...then, as mentioned, start reading at that position after calling
然后定义以下函数
void middle_fseek(FP* FilePointer, int offset)
{
fseek(FilePointer, middle+ offset, SEEK_SET);
}
Then define the following function
void middle_fseek(FP* FilePointer, int offset)
{
fseek(FilePointer, middle+ offset, SEEK_SET);
}