/*
*********************************************************************************************************
*                        INITIALIZE A TASK'S STACK FOR FLOATING POINT EMULATION
*
* Description: This function MUST be called BEFORE calling either OSTaskCreate() or OSTaskCreateExt() in
*              order to initialize the task's stack to allow the task to use the Borland floating-point 
*              emulation.  The returned pointer MUST be used in the task creation call.
*
*              Ex.:   OS_STK TaskStk[1000];
*
*
*                     void main (void)
*                     {
*                         OS_STK *ptos;
*                         OS_STK *pbos;
*                         INT32U  size;
*
*
*                         OSInit();
*                         .
*                         .
*                         ptos = &TaskStk[999];
*                         pbos = &TaskStk[0];
*                         size = 1000;
*                         OSTaskStkInit_FPE_x86(&ptos, &pbos, &size);
*                         OSTaskCreate(Task, (void *)0, ptos, 10);
*                         .
*                         .
*                         OSStart();
*                     }
*
* Arguments  : pptos         is the pointer to the task's top-of-stack pointer which would be passed to 
*                            OSTaskCreate() or OSTaskCreateExt().
*
*              ppbos         is the pointer to the new bottom of stack pointer which would be passed to
*                            OSTaskCreateExt().
*
*              psize         is a pointer to the size of the stack (in number of stack elements).  You 
*                            MUST allocate sufficient stack space to leave at least 384 bytes for the 
*                            floating-point emulation.
*
* Returns    : The new size of the stack once memory is allocated to the floating-point emulation.
*
* Note(s)    : 1) _SS  is a Borland 'pseudoregister' and returns the contents of the Stack Segment (SS)
*              2) The pointer to the top-of-stack (pptos) will be modified so that it points to the new
*                 top-of-stack.
*              3) The pointer to the bottom-of-stack (ppbos) will be modified so that it points to the new
*                 bottom-of-stack.
*              4) The new size of the stack is adjusted to reflect the fact that memory was reserved on
*                 the stack for the floating-point emulation.
*********************************************************************************************************
*/

void  OSTaskStkInit_FPE_x86 (OS_STK **pptos, OS_STK **ppbos, INT32U *psize)
{
    INT32U   lin_tos;                                 /* 'Linear' version of top-of-stack    address   */
    INT32U   lin_bos;                                 /* 'Linear' version of bottom-of-stack address   */
    INT16U   seg;
    INT16U   off;
    INT32U   bytes;


    seg      = FP_SEG(*pptos);                        /* Decompose top-of-stack pointer into seg:off   */
    off      = FP_OFF(*pptos);
    lin_tos  = ((INT32U)seg << 4) + (INT32U)off;      /* Convert seg:off to linear address             */
    bytes    = *psize * sizeof(OS_STK);               /* Determine how many bytes for the stack        */
    lin_bos  = (lin_tos - bytes + 15) & 0xFFFFFFF0L;  /* Ensure paragraph alignment for BOS            */
    
    seg      = (INT16U)(lin_bos >> 4);                /* Get new 'normalized' segment                  */
    *ppbos   = (OS_STK *)MK_FP(seg, 0x0000);          /* Create 'normalized' BOS pointer               */
    memcpy(*ppbos, MK_FP(_SS, 0), 384);               /* Copy FP emulation memory to task's stack      */
    bytes    = bytes - 16;                            /* Loose 16 bytes because of alignment           */
    *pptos   = (OS_STK *)MK_FP(seg, (INT16U)bytes);   /* Determine new top-of-stack                    */
    *ppbos   = (OS_STK *)MK_FP(seg, 384);             /* Determine new bottom-of-stack                 */
    bytes    = bytes - 384;
    *psize   = bytes / sizeof(OS_STK);                /* Determine new stack size                      */
}