转自：http://blog.csdn.net/rrrfff/article/details/6705685
1 bool SetFileLength(const char *FilePath, off_t Length) 2 { 3 #ifdef WIN32 4 System::IO::FileStream *File = System::IO::File::Open(Length, File::OpenMode, File::AllAccess); 5 if (!File) 6 { 7 return false; 8 } 9 /// <summary> 10 /// 表达式调用 File->SetLength() 方法 11 /// 该方法的底层实现是调用NtSetInformationFile 12 /// 并通过 FILE_END_OF_FILE_INFORMATION 结构来设置文件长度 13 /// 该方法的优势是可以直接设置 LONGLONG 型的长度 14 /// </summary> 15 File->Length = Length; 16 delete File; 17 return true; 18 //参考资料 19 //http://msdn.microsoft.com/en-us/library/ff567096(v=VS.85).aspx 20 #else 21 int fd = open(FilePath, O_RDWR); 22 /// <summary> 23 /// -1 if an error occurred 24 /// </summary> 25 if (fd == -1) 26 { 27 return false; 28 } 29 /// <summary> 30 /// On success, zero is returned. On error, -1 is returned, and errno is set appropriately. 31 /// </summary> 32 return ftruncate(fd, Length) == 0; 33 //参考资料 34 //http://api.taocpp.com/doc/path/linux系统调用/文件读写/ftruncate/ 35 //http://linux.die.net/man/2/ftruncate 36 #endif 37 }