windows-nt/Source/XPSP1/NT/enduser/netmeeting/as/dd/shm.c

181 lines
3.5 KiB
C
Raw Normal View History

2020-09-26 03:20:57 -05:00
#include "precomp.h"
//
// SHM.C
// Shared Memory Access, cpi32 and display driver sides both
//
// Copyright(c) Microsoft 1997-
//
//
// SHM_StartAccess
//
LPVOID SHM_StartAccess(int block)
{
LPBUFFER_CONTROL pControl;
LPVOID pMemBlock;
DebugEntry(SHM_StartAccess);
//
// Test for shared memory present
//
ASSERT(g_asSharedMemory != NULL);
//
// Determine which data block we are handling...
//
switch (block)
{
case SHM_OA_DATA:
pControl = &g_asSharedMemory->displayToCore;
break;
case SHM_OA_FAST:
case SHM_BA_FAST:
case SHM_CM_FAST:
pControl = &g_asSharedMemory->fastPath;
break;
default:
ERROR_OUT(("Unknown type %d", block));
break;
}
//
// Mark the double-buffer as busy.
//
pControl->busyFlag = 1;
//
// Set up the current buffer pointer if this is the first access to the
// shared memory.
//
pControl->indexCount++;
if (pControl->indexCount == 1)
{
//
// Set up the 'in use' buffer pointer
//
pControl->currentBuffer = pControl->newBuffer;
//
// Mark the buffer as busy so that the Share Core knows where we
// are.
//
pControl->bufferBusy[pControl->currentBuffer] = 1;
}
//
// Get the pointer to the block to return
//
switch (block)
{
case SHM_OA_DATA:
pMemBlock = g_poaData[pControl->currentBuffer];
break;
case SHM_OA_FAST:
pMemBlock = &(g_asSharedMemory->oaFast[pControl->currentBuffer]);
break;
case SHM_BA_FAST:
pMemBlock = &(g_asSharedMemory->baFast[pControl->currentBuffer]);
break;
case SHM_CM_FAST:
pMemBlock = &(g_asSharedMemory->cmFast[pControl->currentBuffer]);
break;
default:
ERROR_OUT(("Unknown type %d", block));
break;
}
DebugExitPVOID(SHM_StartAccess, pMemBlock);
return(pMemBlock);
}
//
// SHM_StopAccess
//
void SHM_StopAccess(int block)
{
LPBUFFER_CONTROL pControl;
DebugEntry(SHM_StopAccess);
ASSERT(g_asSharedMemory != NULL);
//
// Determine which data block we are handling...
//
switch (block)
{
case SHM_OA_DATA:
pControl = &g_asSharedMemory->displayToCore;
break;
case SHM_OA_FAST:
case SHM_BA_FAST:
case SHM_CM_FAST:
pControl = &g_asSharedMemory->fastPath;
break;
default:
ERROR_OUT(("Unknown type %d", block));
break;
}
//
// Decrement usage count - if we have finally finished with the memory,
// clear the busy flags so that the Share Core knows it won't tread on
// the display driver's toes.
//
pControl->indexCount--;
if (pControl->indexCount == 0)
{
pControl->bufferBusy[pControl->currentBuffer] = 0;
pControl->busyFlag = 0;
}
DebugExitVOID(SHM_StopAccess);
}
#ifdef _DEBUG
//
// SHM_CheckPointer - see shm.h
//
void SHM_CheckPointer(LPVOID ptr)
{
DebugEntry(SHMCheckPointer);
if (ptr == NULL)
{
ERROR_OUT(("Null pointer"));
DC_QUIT;
}
ASSERT(g_asSharedMemory);
if (((LPBYTE)ptr - (LPBYTE)g_asSharedMemory < 0) ||
((LPBYTE)ptr - (LPBYTE)g_asSharedMemory >= SHM_SIZE_USED))
{
ERROR_OUT(("Bad pointer"));
}
DC_EXIT_POINT:
DebugExitVOID(SHM_CheckPointer);
}
#endif // _DEBUG