Dynamic Library Task Switching

Claim 1

A method for providing per-instance data memory in a dynamic link library (DLL) having multiple segments including a segment containing global variables, the DLL being loaded in a random access memory (RAM) address space both as part of a first task and as part of a second task loaded in the RAM address space simultaneously, in a computer having memory management hardware including a local descriptor table (LDT) to map selectors to RAM base addresses, the computer running an operating system that uses a single LDT that is shared among the operating environment and all applications and that loads the DLL so that the segment containing global variables is initially shared by each task accessing the DLL, the method comprising: providing a task switch enhancer DLL (the TSE); providing in the TSE a DLL registration routine to register a DLL with the TSE when the DLL is loaded; providing in the particular DLL a call to the DLL registration routine; providing in the TSE a task registration routine to register a task with the TSE when the task is started; providing in the first task and in the second task a call to the task registration routine; providing in the TSE a routine requesting the operating system to provide the TSE a switching notification whenever execution of any task is about to begin or end and whenever any task is about to cease to exist; providing in the TSE a segment allocation routine for allocating a memory segment for storing per-instance data of a DLL for a task, which allocated segment is a substitute for an original per-instance data segment for that task, the original segment being referenced through a selector in the particular DLL referencing an LDT entry, the segment allocation routine maintaining a substitute base address being a base address for the allocated segment in the LDT entry and maintaining an original base address being the original base address of the original segment in the LDT entry; calling the TSE segment allocation routine for a per-instance data segment of the particular DLL for the first task during initialization of the first task and calling the TSE segment allocation routine for a per-instance data segment of the particular DLL for the second task during initialization of the second task; providing in the TSE a base address setup routine to store in the LDT entry the substitute base address of a per-instance segment of a task before that task begins execution; and invoking the base address setup routine for the substitute base address for the first task in response to a switching notification received by the TSE that the first task is about to begin execution.

Claim 2

A method for providing per-instance data memory in a dynamic link library (DLL) having multiple segments including a segment containing global variables, the DLL being loaded in a random access memory (RAM) address space both as part of a first task and as part of a second task loaded in the RAM address space simultaneously, in a computer having memory management hardware including a local descriptor table (LDT) to map selectors to RAM base addresses, the computer running an operating system that uses a single LDT that is shared among the operating environment and all applications and that loads the DLL so that the segment containing global variables is initially shared by each task accessing the DLL, the method comprising: providing a task switch enhancer DLL (the TSE); providing in the TSE a DLL registration routine to register a DLL with the TSE when the DLL is loaded; providing in the particular DLL a call to the DLL registration routine; providing in the TSE a task registration routine to register a task with the TSE when the task is started; providing in the first task and in the second task a call to the task registration routine; providing in the TSE a routine requesting the operating system to provide the TSE a switching notification whenever execution of any task is about to begin or end and whenever any task is about to cease to exist; providing in the TSE a segment allocation routine for allocating a memory segment for storing per-instance data of a DLL for a task, which allocated segment is a substitute for an original per-instance data segment for that task, the original segment being referenced through a selector in the particular DLL referencing an LDT entry, the segment allocation routine maintaining a substitute base address being a base address for the allocated segment in the LDT entry and maintaining an original base address being the original base address of the original segment in the LDT entry; calling the TSE segment allocation routine for a per-instance data segment of the particular DLL for the first task during initialization of the first task and calling the TSE segment allocation routine for a per-instance data segment of the particular DLL for the second task during initialization of the second task; providing in the TSE a base address setup routine to store in the LDT entry the substitute base address of a per-instance segment of a task before that task begins execution; and invoking the base address setup routine for the substitute base address for the first task in response to a switching notification received by the TSE that the first task is about to begin execution.