Systems and methods for integrating emulated and native code

1. A method for emulating code from an original computer system on a host computer system, the method comprising the steps of:

fetching a program instruction associated with program code to be emulated on a host computer system;

determining whether the program instruction is to be executed natively on the host computer system or is to be emulated on the host computer system; and

if the program instruction is to be executed natively on the host computer system, emitting a native code fragment associated with the program instruction into a dynamic execution layer interface to be executed.

2. The method of claim 1 , wherein the step of fetching a program instruction comprises fetching a program instruction with an emulator.

3. The method of claim 2 , wherein the emulator is an interpreter/emulator.

4. The method of claim 1 , wherein the step of emitting a native code fragment occurs via an application program interface associated with the dynamic execution layer interface.

5. The method of claim 1 , wherein the step of determining whether the program instruction is to be executed natively on the host computer system comprises interfacing a first calling convention associated with an original computer system and a second calling convention associated with the host computer system.

6. The method of claim 1 , wherein the step of determining whether the program instruction is to be executed natively on the host computer system comprises detecting a sentinel instruction.

7. The method of claim 1 , further comprising the step of determining the native code fragment by receiving a data reference to a function that is to be run natively on the host computer system.

8. The method of claim 7 , further comprising the step of determining the native code fragment by receiving a location in memory where native code is located.

9. A system for emulating code from an original computer system on a host computer system, the system comprising:

means for fetching a program instruction associated with program code to be emulated on a host computer system;

means for determining whether the program instruction is to be executed natively on the host computer system or is to be emulated on the host computer system; and

means for emitting a native code fragment associated with the program instruction into a dynamic execution layer interface to be executed in the event that the program instruction is to be executed natively on the host computer system.

10. The system of claim 9 , wherein the means for fetching a program instruction comprises an emulator.

11. The system of claim 9 , wherein the means for emitting a native code fragment comprises an application program interface associated with the dynamic execution layer interface.

12. The system of claim 9 , wherein the means for determining comprises a programming method for interfacing a first calling convention associated with an original computer system and a second calling convention associated with the host computer system.

13. The system of claim 9 , further comprising means for receiving a data reference to a function that is to be run natively on the host computer system.

14. The system of claim 9 , wherein the means for determining a native code fragment comprises a location in memory where native code is located.

15. An emulation program configured to emulate an original computer system for which a program was written, the emulation program stored on a computer-readable medium and comprising:

logic configured to fetch a program instruction associated with program code to be emulated on a host computer system;

logic configured to determine whether the program instruction is to be executed natively on the host computer system or is to be emulated on the host computer system; and

logic configured to emit a native code fragment associated with the program instruction into a dynamic execution layer interface to be executed in the event the program instruction is to be executed natively on the host computer system.

16. The emulation program of claim 15 , wherein the emitting logic is further configure to emit the native code fragment via an application program interface associated with the dynamic execution layer interface.

17. The emulation program of claim 15 , wherein the determining logic is further configured to provide an interface between a first calling convention associated with an original computer system and a second calling convention associated with the host computer system.

18. The emulation program of claim 15 , wherein the determining logic is further configured to detect a sentinel instruction.

19. The emulation program of claim 15 , wherein the determining logic is further configured to receive a data reference a location in memory where native code is located.

20. A system for emulating code from an original computer system on a host computer system, the system comprising:

an emulator configured to fetch instructions associated with a program written to be executed on an original computer system, the emulator comprising an emulation module configured to execute instructions by emulating the original computer system and a native code interceptor module configured to detect instructions that are to be executed natively instead of emulated;

a dynamic execution layer interface including a core having at least one code cache in which code fragments can be cached and executed; and

an application programming interface that links the emulator to the dynamic execution layer interface.

21. The system of claim 20 , wherein the emulator comprises an interpreter/emulator.

22. The system of claim 21 , wherein the emulator further comprises a just-in-time compiler.

23. The system of claim 20 , wherein the application programming interface comprises a set of functions available to the emulator including an emit fragment function with which the emulator can emit code fragments into the at least one code cache and an execute function with which the emulator can request execution of code fragments contained within the at least one code cache.