让 “Thread_example1.pc” 代码在 Linux 平台下编译运行

本文介绍了一个使用多线程进行数据库操作的示例程序，该程序能够在多个线程中执行转账交易，并确保数据一致性。示例展示了如何通过互斥锁来同步线程间的资源访问。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Thread_example1.pc 是《Pro*C/C++ Programmer's Guide》( 10g Release 2 (10.2) ) 的一个多线程示例程序，但其是在UNIX平台下编写的，为能在Linux平台下编译运行，需要做一些改动。下面是Linux 平台下的改动版本。

/*
 * Name:        Thread_example1.pc
 *
 * Description: This program illustrates how to use threading in
 *      conjunction with precompilers. The program creates as many
 *      sessions as there are threads. Each thread executes zero or
 *      more transactions, that are specified in a transient
 *      structure called 'records'.
 * Requirements:
 *      The program requires a table 'ACCOUNTS' to be in the schema
 *      scott/tiger. The description of ACCOUNTS is:
 *  SQL> desc accounts
 *   Name                            Null?    Type
 *  ------------------------------- -------  ------
 *  ACCOUNT                                  NUMBER(36)
 *  BALANCE                                  NUMBER(36,2)
 *
 *  For proper execution, the table should be filled with the accounts
 *      10001 to 10008.
 *
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sqlca.h>

#define      _EXC_OS_        _EXC__UNIX
#define      _CMA_OS_        _CMA__UNIX

#define  DCE_THREADS //[add]
 
#ifdef DCE_THREADS
  #include <pthread.h>
#else
  #include <thread.h>
#endif

/* Function prototypes */
void   err_report();
#ifdef DCE_THREADS
void   do_transaction();
#else
void   *do_transaction();
#endif
void   get_transaction();
void   logon();
void   logoff();

#define CONNINFO "scott/tiger"
#define THREADS  3 

struct parameters 
{ sql_context * ctx;
  int thread_id;
};
typedef struct parameters parameters;

struct record_log
{  char action;
   unsigned int from_account;
   unsigned int to_account;
   float  amount;
};
typedef struct record_log record_log;

record_log records[]= { { 'M', 10001, 10002, 12.50 },
                        { 'M', 10001, 10003, 25.00 },
                        { 'M', 10001, 10003, 123.00 },
                        { 'M', 10001, 10003, 125.00 },
                        { 'M', 10002, 10006, 12.23 },
                        { 'M', 10007, 10008, 225.23 },
                        { 'M', 10002, 10008, 0.70 },
                        { 'M', 10001, 10003, 11.30 },
                        { 'M', 10003, 10002, 47.50 },
                        { 'M', 10002, 10006, 125.00 },
                        { 'M', 10007, 10008, 225.00 },
                        { 'M', 10002, 10008, 0.70 },
                        { 'M', 10001, 10003, 11.00 },
                        { 'M', 10003, 10002, 47.50 },
                        { 'M', 10002, 10006, 125.00 },
                        { 'M', 10007, 10008, 225.00 },
                        { 'M', 10002, 10008, 0.70 },
                        { 'M', 10001, 10003, 11.00 },
                        { 'M', 10003, 10002, 47.50 },
                        { 'M', 10008, 10001, 1034.54}};

static unsigned int trx_nr=0;
#ifdef DCE_THREADS
pthread_mutex_t mutex;
#else
mutex_t mutex;
#endif



/*********************************************************************
 *  Main
 ********************************************************************/
main()
{
  sql_context ctx[THREADS];
#ifdef DCE_THREADS
  pthread_t thread_id[THREADS];
  pthread_attr_t status;
#else
  thread_t thread_id[THREADS];
  int status;
#endif
  parameters params[THREADS];
  int i;
  
  EXEC SQL ENABLE THREADS;

  EXEC SQL WHENEVER SQLERROR DO err_report(sqlca);

  /* Create THREADS sessions by connecting THREADS times */
  for(i=0;i<THREADS;i++)
  {
    printf("Start Session %d....",i);
    EXEC SQL CONTEXT ALLOCATE :ctx[i];
    logon(ctx[i],CONNINFO);
  }

  /*Create mutex for transaction retrieval */
#ifdef DCE_THREADS
  if (pthread_mutex_init(&mutex,NULL))
#else
  if (mutex_init(&mutex, USYNC_THREAD, NULL))
#endif
  {
     printf("Can't initialize mutex\n");
     exit(1);
  }

  /*Spawn threads*/
  for(i=0;i<THREADS;i++)
  {
    params[i].ctx=ctx[i];
    params[i].thread_id=i;

    printf("Thread %d... ",i);
#ifdef DCE_THREADS
    if (pthread_create(&thread_id[i],NULL,
        (void*)do_transaction,
        (void*) ¶ms[i]))
#else
    if (status = thr_create
    (NULL, 0, do_transaction, ¶ms[i], 0, &thread_id[i]))
#endif
      printf("Cant create thread %d\n",i);
    else
      printf("Created\n");
  }


  /* Logoff sessions....*/
  for(i=0;i<THREADS;i++)
  {
     /*wait for thread to end */
     printf("Thread %d ....",i);
#ifdef DCE_THREADS
     if (pthread_join(thread_id[i],NULL))
       printf("Error when waiting for thread % to terminate\n", i);
     else
      printf("stopped\n");

     printf("Detach thread...");
     if (pthread_detach(thread_id[i]))
       printf("Error detaching thread! \n");
     else
       printf("Detached!\n");
#else
     if (thr_join(thread_id[i], NULL, NULL))
       printf("Error waiting for thread to terminate\n");
#endif
     printf("Stop Session %d....",i);
     logoff(ctx[i]);
     EXEC SQL CONTEXT FREE :ctx[i];
  }


  /*Destroys mutex*/
#ifdef DCE_THREADS
  if (pthread_mutex_destroy(&mutex))
#else
  if (mutex_destroy(&mutex))
#endif
  {
    printf("Can't destroy mutex\n");
    exit(1);
  }
}

/*********************************************************************
 * Function: do_transaction
 *
 * Description:  This functions executes one transaction out of the 
 *               records array. The records array is 'managed' by
 *               the get_transaction function.
 *
 *
 ********************************************************************/
#ifdef DCE_THREADS
void do_transaction(params)
#else
void *do_transaction(params)
#endif
parameters *params;
{
  struct sqlca sqlca;
  record_log *trx;
  sql_context ctx=params->ctx;

  /* Done all transactions ? */
  while (trx_nr < (sizeof(records)/sizeof(record_log)))
  {
    get_transaction(&trx);

    EXEC SQL WHENEVER SQLERROR DO err_report(sqlca);
    EXEC SQL CONTEXT USE :ctx;

    printf("Thread %d executing transaction\n",params->thread_id);
    switch(trx->action)
    {
      case 'M':  EXEC SQL UPDATE ACCOUNTS
                          SET    BALANCE=BALANCE+:trx->amount
                          WHERE  ACCOUNT=:trx->to_account;
                 EXEC SQL UPDATE ACCOUNTS
                          SET    BALANCE=BALANCE-:trx->amount
                          WHERE  ACCOUNT=:trx->from_account;
                 break;
       default:  break;
    }
    EXEC SQL COMMIT;
  }
}


/*****************************************************************
 * Function: err_report
 *
 * Description: This routine prints out the most recent error
 *
 ****************************************************************/
void      err_report(sqlca)
struct sqlca sqlca;
{
  if (sqlca.sqlcode < 0)
   printf("\n%.*s\n\n",sqlca.sqlerrm.sqlerrml,sqlca.sqlerrm.sqlerrmc);
  exit(1);
}

/*****************************************************************
 * Function: logon
 *
 * Description: Logs on to the database as USERNAME/PASSWORD
 *
 *****************************************************************/
void      logon(ctx,connect_info)
sql_context ctx;
char * connect_info;
{
    EXEC SQL WHENEVER SQLERROR DO err_report(sqlca);
    EXEC SQL CONTEXT USE :ctx;
    EXEC SQL CONNECT :connect_info;
    printf("Connected!\n");

}

/******************************************************************
 * Function: logoff
 *
 * Description: This routine logs off the database
 *
 ******************************************************************/
void      logoff(ctx)
sql_context ctx;
{
    EXEC SQL WHENEVER SQLERROR DO err_report(sqlca);
    EXEC SQL CONTEXT USE :ctx;
    EXEC SQL COMMIT WORK RELEASE;
    printf("Logged off!\n");
}


/******************************************************************
 * Function: get_transaction
 *
 * Description: This routine returns the next transaction to process
 *
 ******************************************************************/
void get_transaction(trx)
record_log ** trx;
{
#ifdef DCE_THREADS
  if (pthread_mutex_lock(&mutex))
#else
  if (mutex_lock(&mutex))
#endif
    printf("Can't lock mutex\n");

  *trx=&records[trx_nr];

  trx_nr++;

#ifdef DCE_THREADS
  if (pthread_mutex_unlock(&mutex))
#else
  if (mutex_unlock(&mutex))
#endif
    printf("Can't unlock mutex\n");
}