环形内存,circle memory

最新推荐文章于 2025-05-23 09:38:05 发布

原创最新推荐文章于 2025-05-23 09:38:05 发布 · 1.7k 阅读

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typedef struct tagONLY_CIRCLE_MEM
{
UINT32 nMemSize;
UINT8 *pBuf;
UINT8 *pWrite;
UINT8 *pRead;
BOOL bTag; //是否pWrite是在pRead之后
#ifdef WIN32
HMUTEX hBufMutex;
#elif _LINUX
pthread_mutex_t hBufMutex;
#endif
}ONLY_CIRCLE_MEM PACKED;

typedef void* HOCM

HOM ocmAlloc(UINT32 nMemSize)
{
ONLY_CIRCLE_MEM *pOCM = malloc(sizeof(ONLY_CIRCLE_MEM));
if(pOCM==NULL)
  return NULL;
pOCM->pBuf = malloc(nMemSize);
if(pOCM->pBuf==NULL)
{
  free(pOCM);
  return NULL;
}
pOCM->pWrite = pOCM->pBuf;
pOCM->pRead = pOCM->pBuf;
pOCM->nMemSize = nMemSize;
pOCM->bTag = TRUE;
#ifdef WIN32
pOCM->hBufMutex=CreateMutex(NULL, FALSE, NULL);
#elif _LINUX
pOCM->hBufMutex = (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;
#endif
return pOCM;
}

void ocmFree(HOCM hocm)
{
ONLY_CIRCLE_MEM *pOCM =(ONLY_CIRCLE_MEM*)hocm;
if(pOCM==NULL)
return;
#ifdef WIN32
CloseHandle(pOCM->hBufMutex);
#elif _LINUX
pthread_mutex_destroy(&pOCM->hBufMutex);
#endif
if(pOCM->pBuf!=NULL)
{
free(pOCM->pBuf);
}
pOCM->pRead = NULL;
pOCM->pWrite = NULL;
free(pOCM);
}

UINT32 ocmPut(HOCM hocm, void *pBuf, UINT32 nBufLen)
{
ONLY_CIRCLE_MEM *pOCM = (ONLY_CIRCLE_MEM*)hocm;
UINT32 nLeftLen=nBufLen;
INT32 rc;

if(pOCM==NULL || pOCM->pBuf ==NULL)
{
return 0;
}

#ifdef WIN32
WaitForSingleObject(pOCM->hBufMutex, INFINITE);
#elif _LINUX
rc = pthread_mutex_lock(&pOCM->hBufMutex);
if(rc)
{
printf("Cannot lock the thread mutex\n");
pthread_exit(NULL);
}
#endif

while(nLeftLen>0)
{
  if(pOCM->bTag)
  {
   if(   pOCM ->pBuf+pOCM->nMemSize-pOCM->pWrite>nLeftLen)
   {
    memcpy(pOCM->pWrite, (UINT8*)pBuf+(nBufLen-nLeftLen), nLeftLen);
    pOCM->pWrite += nLeftLen;
    nLeftLen = 0;
   }
   else
   {
    memcpy(pOCM->pWrite, (UINT8*)pBuf+(nBufLen-nLeftLen), pOCM->pBuf+pOCM->nMemSize-pOCM->pWrite);
    nLeftLen -= pOCM->pBuf+pOCM->nMemSize-pOCM->pWrite;
    pOCM->pWrite = pOCM->pBuf;
    pOCM->bTag = FALSE;
   }
  }
  else
  {
   if(pOCM->pRead-pOCM->pWrite>nLeftLen)
   {
    memcpy(pOCM->pWrite, (UINT8*)pBuf+(nBufLen-nLeftLen), nLeftLen);
    pOCM->pWrite += nLeftLen;
    nLeftLen=0;
   }
   else
   {
    memcpy(pOCM->pWrite, (UINT8*)pBuf+(nBufLen-nLeftLen), pOCM->pRead-pOCM->pWrite);
    nLeftLen -= pOCM->pRead-pOCM->pWrite;
    pOCM->pWrite = pOCM->pRead;
    break;
   }

  }
}

#ifdef WIN32
ReleaseMutex(pOCM->hBufMutex);
#elif _LINUX
rc = pthread_mutex_unlock(&pOCM->hBufMutex);
if(rc)
{
  printf("Cannot unlock the thread mutex\n");
  pthread_exit(NULL);
}
#endif
return nBufLen-nLeftLen;
}

UINT32 ocmGet(HOM hocm, void *pBuf, UINT32 nDataLen)
{
ONLY_CIRCLE_MEM *pOCM = (ONLY_CIRCLE_MEM*)hocm;
UINT32 nLeftLen=nDataLen;
INT32 rc;
if(pOCM==NULL ||pOCM->pBuf==NULL)
{
  return 0;
}
#ifdef WIN32
WaitForSingleObject(pOCM->hBufMutex, INFINITE);
#elif _LINUX
rc = pthread_mutex_lock(&pOCM->hBufMutex);
if(rc)
{
  printf("Cannot lock the thread mutex\n");
  pthread_exit(NULL);
}
#endif
while(nLeftLen>0)
{
  if(pOCM->bTag)
  {
   if(pOCM->pWrite-pOCM->pRead >nLeftLen)
   {
    memcpy((UINT8*)pBuf+(nDataLen-nLeftLen), pOCM->pRead, nLeftLen);
    pOCM->pRead += nLeftLen;
    nLeftLen = 0;
   }
   else
   {
    memcpy((UINT8*)pBuf+(nDataLen-nLeftLen), pOCM->pRead, pOCM->pWrite-pOCM->pRead);
    nLeftLen -= (pOCM->pWrite-pOCM->pRead);
    pOCM->pRead = pOCM->pWrite;
    break;
   }
  }
  else
  {
   if(pOCM->pBuf+pOCM->nMemSize-pOCM->pRead>nLeftLen)
   {
    memcpy((UINT8*)pBuf+(nDataLen-nLeftLen), pOCM->pRead, nLeftLen);
    pOCM->pRead+=nLeftLen;
    nLeftLen=0;
   }
   else
   {
    memcpy((UINT8*)pBuf+(nDataLen-nLeftLen), pOCM->pRead, pOCM->pBuf+pOCM->nMemSize-pOCM->pRead);
    nLeftLen -= pOCM->pBuf+pOCM->nMemSize-pOCM->pRead;
    pOCM->pRead = pOCM->pBuf;
    pOCM->bTag = TRUE;
   }

  }
}
#ifdef WIN32
ReleaseMutex(pOCM->hBufMutex);
#elif _LINUX
rc = pthread_mutex_unlock(&pOCM->hBufMutex);
if(rc)
{
  printf("Cannot unlock the thread mutex\n");
  pthread_exit(NULL);
}
#endif
return nDataLen-nLeftLen;
}

只给出部分代码，不讲解。注意开头的那个结构体中的BOOL bTag; 的重要作用