作者：朱金燦

來源：http://blog.csdn.net/clever101

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??????? 在并發(fā)訪問sqlite數(shù)據(jù)庫會出現(xiàn)這樣一個錯誤：databseis locked，這是sqlite數(shù)據(jù)庫對并發(fā)支持不太好的緣故造成的。采用網(wǎng)上的一種的思路是通過互斥信號量來達(dá)到并發(fā)訪問的目的。下面是一個跨平臺的互斥信號量類：

//ProcessMutex.h文件： 
#ifndef __PROCESS_MUTEX_H__
#define __PROCESS_MUTEX_H__
 
#if defined _WIN32 || defined _WIN64

     #include 

#endif
 
#ifdef linux
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#endif
 
class CProcessMutex
{
public:
    /* 默認(rèn)創(chuàng)建匿名的互斥 */
    CProcessMutex(const char* name = NULL);
    ~CProcessMutex();
 
    bool Lock();
    bool UnLock();
private:

#if defined _WIN32 || defined _WIN64

    void* m_pMutex;

#endif

#ifdef linux
    set_t* m_pSem;
#ednif
    char m_cMutexName[30];
};
#endif

 //ProcessMutex.cpp文件：
#include "ProcessMutex.h"
 
#if defined _WIN32 || defined _WIN64
 
CProcessMutex::CProcessMutex(const char* name)
{
    memset(m_cMutexName, 0 ,sizeof(m_cMutexName));
    int min = strlen(name)>(sizeof(m_cMutexName)-1)?(sizeof(m_cMutexName)-1):strlen(name);
    strncpy(m_cMutexName, name, min);
    m_pMutex = CreateMutex(NULL, false, m_cMutexName);
}
 
CProcessMutex::~CProcessMutex()
{
    CloseHandle(m_pMutex);
}
 
bool CProcessMutex::Lock()
{
    //互斥鎖創(chuàng)建失敗
    if (NULL == m_pMutex)
    {
        return false;
    }
     
    DWORD nRet = WaitForSingleObject(m_pMutex, INFINITE);
    if (nRet != WAIT_OBJECT_0)
    {
        return false;
    }
 
    return true;
}
 
bool CProcessMutex::UnLock()
{
    return ReleaseMutex(m_pMutex);
}
 
#endif
 
#ifdef linux
 
CProcessMutex::CProcessMutex(const char* name)
{
    memset(m_cMutexName, 0 ,sizeof(m_cMutexName));
    int min = strlen(name)>(sizeof(m_cMutexName)-1)?(sizeof(m_cMutexName)-1):strlen(name);
    strncpy(m_cMutexName, name, min);
    m_pSem = sem_open(name, O_CREAT, 0644, 1);
}
 
CProcessMutex::~CProcessMutex()
{
    int ret = sem_close(m_pSem);
    if (0 != ret)
    {
        printf("sem_close error %dn", ret);
    }
    sem_unlink(m_cMutexName);
}
 
bool CProcessMutex::Lock()
{
    int ret = sem_wait(m_pSem);
    if (ret != 0)
    {
        return false;
    }
    return true;
}
 
bool CProcessMutex::UnLock()
{
    int ret = sem_post(m_pSem);
    if (ret != 0)
    {
        return false;
    }
    return true;
}
 
#endif

使用示例代碼如下：

CProcessMutex pMutex("MutexName");

pMutex.Lock();

sqlite3_exec( myconn, sql, 0, 0, &m_sqlerr_msg); // 執(zhí)行sqlite的相關(guān)操作

pMutex.UnLock();

參考文獻(xiàn)：

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1. 多進(jìn)程之間的互斥信號量的實(shí)現(xiàn)（Linux和windows跨平臺）

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2.sqlite遇到database is locked問題的完美解決