Chapter 4 Using Crypto-C 119
System Considerations In Crypto-C
Chapter 1 also gives the form that a surrender function must have:
If you define a surrender function within the surrender context, Crypto-C functions
will call it at regular intervals during execution. Depending on the application, the
surrender function can perform one of a number of operations.
For example, a surrender function can:
•Notify the user of the current status of execution, either once at the beginning or
once every second, for instance.
•Allow the user to cancel the operation.
•Suspend the Crypto-C function to allow other operations to execute.
Even when you do not need a surrender function to manage lengthy function calls,
you can create one to perform other tasks. For example, you could use a surrender
function to allow other applications to cut into a Crypto-C routine, no matter how
quickly the routine executes. A surrender context is a potent debugging tool as well.
A Sample Surrender Function
As an example, we will construct a surrender function that announces the start of a
Crypto-C function, and prints out a dot on the screen every second.
typedef struct {
int (*Surrender) (POINTER); /* surrender function callback */
POINTER handle; /* application-specific information */
POINTER reserved; /* reserved for future use */
} A_SURRENDER_CTX;
int (*Surrender) (
POINTER handle /* application-specific information */
);
#include <time.h>
int GeneralSurrenderFunction (handle)
POINTER handle;
{
static time_t currentTime;
time_t getTime;