.NET/Java PDF, Tiff, Barcode SDK Library

Since the caller of the virtual functions is a native caller, it simply picks a function pointer from a vtable to invoke the virtual function. When a virtual function is compiled to managed code, a pointer to the thunk must end up in the vtable. To create this thunk, the compiler produces .vtentry and .vtfixup metadata for the methods F1 and F2 of SampleClass: .method assembly static void modopt([mscorlib]System.Runtime.CompilerServices.CallConvThiscall) SampleClass.F1( valuetype SampleClass* modopt([mscorlib]System.Runtime.CompilerServices.IsConst) modopt([mscorlib]System.Runtime.CompilerServices.IsConst) this ) cil managed { .vtentry 1 : 1 // IL code elided for clarity here } Figure 9-8 shows the opposite direction of managed-unmanaged transitions and virtual function calls. Here, a managed caller (main) invokes a native virtual function (F2).

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You ve already seen in the section on data security how you can use roles to encapsulate privileges rather than granting privileges directly to various users. You should minimize the number of direct object privileges by letting stored code such as procedures and packages be the means through which users can issue DML statements. Then you can just grant the user the privilege to execute a certain package or procedure to perform any DML actions. Once the package or procedure completes executing, the user will not have the privilege to perform the DML activity from outside the stored code.

The first is the pid of the process that should be at the root of the tree. The second is a string that will be prepended to the information about a process to form a line of displayed output. This string contains the characters that depict the tree-branch structure leading up to a tree leaf. The first time the function is called (from the main() function discussed earlier) the second argument is set to null because the root of the process tree has no branches leading into it. This function is used recursively to process the tree level-by-level. As you can see by examining the sample output shown earlier, the ASCII characters needed to print out a particular process branch are determined by the branch s level in the tree and whether it is the last child of its parent. When we recursively descend one level in the tree to the next child, this adds one more straight branch symbol and an appropriate slanted branch (or space) leading into the child. This is where the output of the process ID, owner and command are printed. You can add more information, such as parent pid or CPU time, but you would have to modify the main function.

All application roles should use the SET ROLE statement to enable the roles granted to users. Application users should be granted roles only for specific purposes, and the roles should be revoked from them when they aren t needed any longer. Application owners should consider creating secure application roles, which are enabled by PL/SQL packages. Once you create and assign a secure application role to a user, it automatically gets assigned to the user when the user logs in to the database.

One of the first things you should do when opening your database to the public is to tightly restrict the ability of users to use the SQL*Plus interface. You can restrict the SQL*Plus capabilities of a user by using the product_user_profile table.

In this section you ll examine some simple scripts that can help you manage your users. You ll also learn about some typical problems that you might encounter in this area.

The following code shows how to alter a user s profile: SQL> ALTER PROFILE fin_user 2 LIMIT 3 FAILED_LOGIN_ATTEMPTS 5 4 PASSWORD_LOCK_TIME 1; Profile altered. SQL>

echo "$2$id" ${owner[$id]} ${command[$id]}

You can use the DBA_USERS view to get quite a bit of information about the user population in your database. Here s a typical query using the DBA_USERS view: SQL> SELECT username, profile, account, status FROM dba_users; USERNAME PROFILE ACCOUNT_STATUS --------------------------------------------------------------SYS DEFAULT OPEN SYSTEM DEFAULT OPEN OUTLN DEFAULT OPEN DBSNMP DEFAULT OPEN HARTSTEIN DEFAULT OPEN FINANCE DEFAULT OPEN SQL>

Figure 9-8. Calling managed virtual functions from native code To call the native virtual function F2, the managed caller uses the IL instructions for virtual memory access discussed in 8 to determine the address to the virtual function pointer from the vtable. Once the virtual function pointer is obtained, the function can be called via the CALLI instruction. For the call p->F2(), the compiler emits the following IL code: ldloc p // Push SampleClass pointer on the stack (later used as this argument for call)