逆向工程位掩码以获取权限列表

Question

我正在使用bitmasks表示的权限。这些权限是

$permissionMap = [
    'VIEW'     => 1;
    'CREATE'   => 2;
    'EDIT'     => 4;
    'DELETE'   => 8
    'UNDELETE' => 16;         
    'OPERATOR' => 32;         
    'MASTER'   => 64;         
    'OWNER'    => 128;
];       

如果我合并多个权限，请说VIEW，EDIT和DELETE以获取13的位掩码。是否可以对该整数进行反向工程以了解所使用的权限创造它？

function getPermissions($mask, $permissionMap) {
    // use $permissionMap to return string[] 
}

$viewEditAndDelete = 1 | 4 | 8; // 13

getPermissions($viewEditAndDelete, $permissionMap); // ['VIEW', 'EDIT', 'DELETE']

Answer 1

只检查是否设置了特定的面具。如果我们遍历$map并检查其标志是否已设置，那么它实际上非常简单：

function getPermissions($mask, $permissionMap) {
    $permissions = [];
    foreach( $permissionMap as $perm => $val )
        if( $mask & $val )
            array_push( $permissions, $perm );
    return $permissions;
}