DosAllocThreadLocalMemory

Description

Allocates a block of memory that is local to a thread.

APIRET DosAllocThreadLocalMemory (ULONG Lwords, PPVOID pMemBlock)

Lwords (ULONG) - input The number of 32-bit dwords to allocate.
pMemBlock (PPVOID) - input
A pointer to the memory block allocated.

DosAllocThreadLocalMemory returns the following values:

NO_ERROR

ERROR_NOT_ENOUGH_MEMORY

ERROR_INVALID_PATAMETER

When a process is started, a small block of memory is set aside to be used as a thread-local memory area. This memory is at the same virtual address for each thread, but is backed by different physical memory. This permits each thread to have a small block of memory that is unique, or local, to that thread.

The thread-local memory area consists of 32 DWORDs (128 bytes), each DWORD being 32-bits in size. Up to 8 DWORDs (32 bytes) can be requested each time this function is called. If you want to allocate more than 8 DWORDs, you must call this function more than once.

Allocation is by DWORD only. If you want to store a BYTE in the thread-local memory area, you would still allocate a DWORD, then store the BYTE in it.

DosFreeThreadLocalMemory

The following code example allocates a thread-local memory block of 6 DWORDs, then frees it.

  #define  INCL_DOSPROCESS  /* Memory Manager values */
  #include <os2.h>

  #include <stdio.h>  /* For printf */

  PVOID    pMemBlock;     /* Pointer to the memory block returned */
  APIRET   rc;            /* Return code */

     rc = DosAllocThreadLocalMemory(6, &pMemBlock);   /* Allocate 6 DWORDs */

     if (rc != NO_ERROR)
     {
         printf("DosAllocThreadLocalMemory error: return code = %ld", rc);
         return 1;
     }


     /* ... Use the thread-local memory block ... */


     rc = DosFreeThreadLocalMemory(pMemBlock);     /* Free the memory block */

     if (rc != NO_ERROR)
     {
         printf("DosFreeThreadLocalMemory error: return code = %ld", rc);
         return 1;
     }

     return 0;