181 lines
4 KiB
C++
181 lines
4 KiB
C++
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/*****************************************************************/
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/** Microsoft Windows for Workgroups **/
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/** Copyright (C) Microsoft Corp., 1993-1994 **/
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/*****************************************************************/
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/* npcrit.c -- Implementation of critical section classes.
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*
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* History:
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* 11/01/93 gregj Created
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*/
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#include "npcommon.h"
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#include <npcrit.h>
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#include <npassert.h>
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/*
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* Very simple interlock routines, used to stop race conditions when
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* initializing and de-initializing critical sections. Do NOT use
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* these for anything other than infrequent extremely short-term locks,
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* since WaitForInterlock contains a spin loop with a millisecond delay!
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*/
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BYTE InterlockedSet(volatile BYTE *pByte)
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{
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BYTE bRet;
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_asm {
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mov edi, pByte
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mov al, 1
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xchg [edi], al /* store non-zero value, get what was there before */
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mov bRet, al
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}
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return bRet;
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}
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void WaitForInterlock(volatile BYTE *pByte)
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{
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for (;;) {
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BYTE bAlreadyOwned = InterlockedSet(pByte); /* attempt to grab the interlock */
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if (!bAlreadyOwned) /* is someone else in there? */
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break; /* nope, we now own it */
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Sleep(1); /* yield to whomever owns it, then try again */
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}
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}
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void ReleaseInterlock(volatile BYTE *pByte)
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{
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*pByte = 0; /* clear the interlock to release others */
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}
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#if 0
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// Remove CRITSEC code but keep for a while before deleting.
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/*******************************************************************
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NAME: CRITSEC::Init
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SYNOPSIS: Initializes a global critical section object
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ENTRY: pszName - name for the critical section
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EXIT: No return value
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NOTES: Currently pszName is not used; it will be used
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for named mutexes later.
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HISTORY:
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gregj 11/01/93 Created
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********************************************************************/
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void CRITSEC::Init(char *pszName)
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{
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WaitForInterlock(&_bInterlock);
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if (!_fInitialized) {
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::InitializeCriticalSection(&_critsec);
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#ifdef DEBUG
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_wClaimCount = 0;
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#endif
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_fInitialized = 1;
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}
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ReleaseInterlock(&_bInterlock);
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_cClients++;
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}
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/*******************************************************************
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NAME: CRITSEC::Term
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SYNOPSIS: Cleans up resources allocated for a critical section
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ENTRY: No parameters
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EXIT: No return value
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NOTES: This function should be callled at process attach.
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It will take care of making sure it only deletes
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the critical section when the last process using
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it calls Term().
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HISTORY:
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gregj 11/01/93 Created
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********************************************************************/
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void CRITSEC::Term()
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{
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WaitForInterlock(&_bInterlock);
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BOOL fShouldCleanUp = (--_cClients == 0);
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if (fShouldCleanUp) {
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::DeleteCriticalSection(&_critsec);
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_fInitialized = 0;
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}
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ReleaseInterlock(&_bInterlock);
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}
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#ifdef DEBUG /* in retail, these are inline */
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/*******************************************************************
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NAME: CRITSEC::Enter
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SYNOPSIS: Enters a critical section
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ENTRY: No parameters
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EXIT: No return value; critical section is owned by
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the calling thread
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NOTES: This function is private, and is invoked indirectly
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by the friend class TAKE_CRITSEC.
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HISTORY:
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gregj 11/01/93 Created
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********************************************************************/
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void CRITSEC::Enter()
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{
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#ifdef DEBUG
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UIASSERT(_fInitialized != 0);
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#endif
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::EnterCriticalSection(&_critsec);
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#ifdef DEBUG
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_wClaimCount++;
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#endif
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}
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/*******************************************************************
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NAME: CRITSEC::Leave
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SYNOPSIS: Leaves a critical section
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ENTRY: No parameters
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EXIT: No return value; critical section is released
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NOTES: This function is private, and is invoked indirectly
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by the friend class TAKE_CRITSEC.
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HISTORY:
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gregj 11/01/93 Created
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********************************************************************/
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void CRITSEC::Leave()
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{
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#ifdef DEBUG
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UIASSERT(_fInitialized != 0);
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UIASSERT(_wClaimCount > 0);
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_wClaimCount--;
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#endif
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::LeaveCriticalSection(&_critsec);
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}
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#endif /* DEBUG */
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#endif /* 0 */
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