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Annotation of os2sdk/demos/examples/vioreg/viosub.c, revision 1.1.1.1

1.1       root        1: /* This routine is the viosubsystem replacement routine for           */
                      2: /* VioWrtTTy.  It does nothing but increment counters in shared        */
                      3: /* memory that have been allocated in REGISTER.  Access to the shared  */
                      4: /* memory is interleaved with ACCESS, which prints the contents of the */
                      5: /* counters.                                                          */
                      6: /*                                                                    */
                      7: /*   Created by Microsoft Corp. 1988                                  */
                      8: 
                      9: #define INCL_DOSSEMAPHORES
                     10: #define INCL_DOSMEMMGR
                     11: 
                     12: #include <os2def.h>
                     13: #include <bsedos.h>
                     14: #include <stdio.h>
                     15: #include "share.h"    /* Common declarations between processes */
                     16: 
                     17: int _acrtused=0;  /* _acrtused must be declared in one of the modules  */
                     18:                  /* of the dll. The C compiler generates this symbol  */
                     19:                  /* as an extern to ensure that the runtime library   */
                     20:                  /* startup module crt0 will be pulled in by the      */
                     21:                  /* linker.  Declaring _acrtused will keep this       */
                     22:                  /* unwanted code out.                                */
                     23: 
                     24: /* The VIO router places the VioWrtTTy parameters on the stack, along  */
                     25: /* with the registered routine's (VioWrtTTy) address and index, the    */
                     26: /* entry point in the VIO router, the caller's DS and the dynamic      */
                     27: /* link entry point.  The replacement router places the contents of    */
                     28: /* registers BP and DI on the stack, and then copies the parameters    */
                     29: /* on the stack again. Declaring the replacement routine as pascal    */
                     30: /* allows proper access to the parameters.                            */
                     31: 
                     32: 
                     33: int APIENTRY REPLACE(Charstr,length, handle)
                     34: PCH Charstr;        /* These three are the parameters for        */
                     35: USHORT length;      /* VioWrtTTy                                 */
                     36: SHANDLE handle;
                     37: 
                     38: {    SEL Selector;                 /* Shared memory selector */
                     39:      struct ShareRec far *SmemPtr;  /* Shared memory layout, described
                     40:                                       in Share.h  */
                     41:      int rc;                       /* Return code */
                     42: 
                     43:      DosGetShrSeg(SHRSEGNAME, &Selector);
                     44: 
                     45:      /* Get a far pointer from a 16 bit selector */
                     46:      SmemPtr = (struct ShareRec far *)MAKEP(Selector,0);
                     47: 
                     48:      DosSemRequest((HSEM)&(SmemPtr->mutexsem), WAITFOREVER);
                     49:      SmemPtr->count++;
                     50: 
                     51:      /* Increment the total length, using the length parameter */
                     52:      SmemPtr->totalength += length;
                     53: 
                     54:      /* Updated is set in ACCESS, and cleared here, creating the
                     55:        interleaving  */
                     56:      DosSemClear((HSEM)&(SmemPtr->updated));
                     57:      DosSemClear((HSEM)&(SmemPtr->mutexsem));
                     58: 
                     59:      /* Must use DosFreeSeg in order to decrement the reference
                     60:        counter to the shared memory segment.  The segment will
                     61:        not be deallocated until the reference count is 0, this
                     62:        will not happen because DosGetShrSeg increments the reference
                     63:        counter, and there is one DosGetShrSeg call in REGISTER. */
                     64:      DosFreeSeg(Selector);
                     65: 
                     66:      /* Returning -1 causes the VIO router to invoke the replaced
                     67:        routine, i.e. VioWrtTTy */
                     68:      return(-1);
                     69: }

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