c++中的位域

typedef unsigned int Bit; class File { Bit mode: 2; Bit modified: 1; Bit prot_owner: 3; Bit prot_group: 3; Bit prot_world: 3; // ... };

几个段堆积成一个integer

 

void File::write() { modified = 1; // ... } void File::close() { if (modified) // ... save contents }

 

enum { READ = 01, WRITE = 02 }; // File modes int main() { File myFile; myFile.mode |= READ; // set the READ bit if (myFile.mode & READ) // if the READ bit is on cout << "myFile.mode READ is set\n"; }

inline int File::isRead() { return mode & READ; } inline int File::isWrite() { return mode & WRITE; } if (myFile.isRead()) /* ... */

 

The address-of operator (&) cannot be applied to a bit-field, so there can be no pointers referring to class bit-fields. Nor can a bit-field be a static member of its class