缓冲区的使用
// 这是per-I/O数据。它包含了在套节字上处理I/O操作的必要信息
struct CIOCPBuffer
{
WSAOVERLAPPED ol;
SOCKET sClient; // AcceptEx接收的客户方套节字
char *buff; // I/O操作使用的缓冲区
int nLen; // buff缓冲区(使用的)大小
ULONG nSequenceNumber; // 此I/O的序列号
int nOperation; // 操作类型
#define OP_ACCEPT 1
#define OP_WRITE 2
#define OP_READ 3
CIOCPBuffer *pNext;
};
//------------------------------------
CIOCPBuffer *CIOCPServer::AllocateBuffer(int nLen)
{
CIOCPBuffer *pBuffer = NULL;
if(nLen > BUFFER_SIZE)
return NULL;
// 为缓冲区对象申请内存
::EnterCriticalSection(&m_FreeBufferListLock);
if(m_pFreeBufferList == NULL) // 内存池为空,申请新的内存
{
pBuffer = (CIOCPBuffer *)::HeapAlloc(GetProcessHeap(),
HEAP_ZERO_MEMORY, sizeof(CIOCPBuffer) + BUFFER_SIZE);
}
else // 从内存池中取一块来使用
{
pBuffer = m_pFreeBufferList;
m_pFreeBufferList = m_pFreeBufferList->pNext;
pBuffer->pNext = NULL;
m_nFreeBufferCount --;
}
::LeaveCriticalSection(&m_FreeBufferListLock);
// 初始化新的缓冲区对象
if(pBuffer != NULL)
{
pBuffer->buff = (char*)(pBuffer + 1);
pBuffer->nLen = nLen;
}
return pBuffer;
}
真的很不明白:pBuffer->buff = (char*)(pBuffer + 1);是做什么?
请高人指点!