Redis教程(十五)：C語言連接操作代碼實例

#include stdio.h>
#include stdlib.h>
#include stddef.h>
#include stdarg.h>
#include string.h>
#include assert.h>
#include hiredis.h>

void doTest()
{
  int timeout = 10000;
  struct timeval tv;
  tv.tv_sec = timeout / 1000;
  tv.tv_usec = timeout * 1000;
  //以帶有超時的方式鏈接Redis服務(wù)器，同時獲取與Redis連接的上下文對象。
  //該對象將用于其后所有與Redis操作的函數(shù)。
  redisContext* c = redisConnectWithTimeout("192.168.149.137",6379,tv);
  if (c->err) {
    redisFree(c);
    return;
  }
  const char* command1 = "set stest1 value1";
  redisReply* r = (redisReply*)redisCommand(c,command1);
  //需要注意的是，如果返回的對象是NULL，則表示客戶端和服務(wù)器之間出現(xiàn)嚴重錯誤，必須重新鏈接。
  //這里只是舉例說明，簡便起見，后面的命令就不再做這樣的判斷了。
  if (NULL == r) {
    redisFree(c);
    return;
  }
  //不同的Redis命令返回的數(shù)據(jù)類型不同，在獲取之前需要先判斷它的實際類型。
  //至于各種命令的返回值信息，可以參考Redis的官方文檔，或者查看該系列博客的前幾篇
  //有關(guān)Redis各種數(shù)據(jù)類型的博客。:)
  //字符串類型的set命令的返回值的類型是REDIS_REPLY_STATUS，然后只有當返回信息是"OK"
  //時，才表示該命令執(zhí)行成功。后面的例子以此類推，就不再過多贅述了。
  if (!(r->type == REDIS_REPLY_STATUS  strcasecmp(r->str,"OK") == 0)) {
    printf("Failed to execute command[%s].\n",command1);
    freeReplyObject(r);
    redisFree(c);
    return;
  }
  //由于后面重復(fù)使用該變量，所以需要提前釋放，否則內(nèi)存泄漏。
  freeReplyObject(r);
  printf("Succeed to execute command[%s].\n",command1);

  const char* command2 = "strlen stest1";
  r = (redisReply*)redisCommand(c,command2);
  if (r->type != REDIS_REPLY_INTEGER) {
    printf("Failed to execute command[%s].\n",command2);
    freeReplyObject(r);
    redisFree(c);
    return;
  }
  int length = r->integer;
  freeReplyObject(r);
  printf("The length of 'stest1' is %d.\n",length);
  printf("Succeed to execute command[%s].\n",command2);

  const char* command3 = "get stest1";
  r = (redisReply*)redisCommand(c,command3);
  if (r->type != REDIS_REPLY_STRING) {
    printf("Failed to execute command[%s].\n",command3);
    freeReplyObject(r);
    redisFree(c);
    return;
  }
  printf("The value of 'stest1' is %s.\n",r->str);
  freeReplyObject(r);
  printf("Succeed to execute command[%s].\n",command3);

  const char* command4 = "get stest2";
  r = (redisReply*)redisCommand(c,command4);
  //這里需要先說明一下，由于stest2鍵并不存在，因此Redis會返回空結(jié)果，這里只是為了演示。
  if (r->type != REDIS_REPLY_NIL) {
    printf("Failed to execute command[%s].\n",command4);
    freeReplyObject(r);
    redisFree(c);
    return;
  }
  freeReplyObject(r);
  printf("Succeed to execute command[%s].\n",command4);

  const char* command5 = "mget stest1 stest2";
  r = (redisReply*)redisCommand(c,command5);
  //不論stest2存在與否，Redis都會給出結(jié)果，只是第二個值為nil。
  //由于有多個值返回，因為返回應(yīng)答的類型是數(shù)組類型。
  if (r->type != REDIS_REPLY_ARRAY) {
    printf("Failed to execute command[%s].\n",command5);
    freeReplyObject(r);
    redisFree(c);
    //r->elements表示子元素的數(shù)量，不管請求的key是否存在，該值都等于請求是鍵的數(shù)量。
    assert(2 == r->elements);
    return;
  }
  for (int i = 0; i  r->elements; ++i) {
    redisReply* childReply = r->element[i];
    //之前已經(jīng)介紹過，get命令返回的數(shù)據(jù)類型是string。
    //對于不存在key的返回值，其類型為REDIS_REPLY_NIL。
    if (childReply->type == REDIS_REPLY_STRING)
      printf("The value is %s.\n",childReply->str);
  }
  //對于每一個子應(yīng)答，無需使用者單獨釋放，只需釋放最外部的redisReply即可。
  freeReplyObject(r);
  printf("Succeed to execute command[%s].\n",command5);

  printf("Begin to test pipeline.\n");
  //該命令只是將待發(fā)送的命令寫入到上下文對象的輸出緩沖區(qū)中，直到調(diào)用后面的
  //redisGetReply命令才會批量將緩沖區(qū)中的命令寫出到Redis服務(wù)器。這樣可以
  //有效的減少客戶端與服務(wù)器之間的同步等候時間，以及網(wǎng)絡(luò)IO引起的延遲。
  //至于管線的具體性能優(yōu)勢，可以考慮該系列博客中的管線主題。
  if (REDIS_OK != redisAppendCommand(c,command1)
    || REDIS_OK != redisAppendCommand(c,command2)
    || REDIS_OK != redisAppendCommand(c,command3)
    || REDIS_OK != redisAppendCommand(c,command4)
    || REDIS_OK != redisAppendCommand(c,command5)) {
    redisFree(c);
    return;
  }

  redisReply* reply = NULL;
  //對pipeline返回結(jié)果的處理方式，和前面代碼的處理方式完全一直，這里就不再重復(fù)給出了。
  if (REDIS_OK != redisGetReply(c,(void**)reply)) {
    printf("Failed to execute command[%s] with Pipeline.\n",command1);
    freeReplyObject(reply);
    redisFree(c);
  }
  freeReplyObject(reply);
  printf("Succeed to execute command[%s] with Pipeline.\n",command1);

  if (REDIS_OK != redisGetReply(c,(void**)reply)) {
    printf("Failed to execute command[%s] with Pipeline.\n",command2);
    freeReplyObject(reply);
    redisFree(c);
  }
  freeReplyObject(reply);
  printf("Succeed to execute command[%s] with Pipeline.\n",command2);

  if (REDIS_OK != redisGetReply(c,(void**)reply)) {
    printf("Failed to execute command[%s] with Pipeline.\n",command3);
    freeReplyObject(reply);
    redisFree(c);
  }
  freeReplyObject(reply);
  printf("Succeed to execute command[%s] with Pipeline.\n",command3);

  if (REDIS_OK != redisGetReply(c,(void**)reply)) {
    printf("Failed to execute command[%s] with Pipeline.\n",command4);
    freeReplyObject(reply);
    redisFree(c);
  }
  freeReplyObject(reply);
  printf("Succeed to execute command[%s] with Pipeline.\n",command4);

  if (REDIS_OK != redisGetReply(c,(void**)reply)) {
    printf("Failed to execute command[%s] with Pipeline.\n",command5);
    freeReplyObject(reply);
    redisFree(c);
  }
  freeReplyObject(reply);
  printf("Succeed to execute command[%s] with Pipeline.\n",command5);
  //由于所有通過pipeline提交的命令結(jié)果均已為返回，如果此時繼續(xù)調(diào)用redisGetReply，
  //將會導致該函數(shù)阻塞并掛起當前線程，直到有新的通過管線提交的命令結(jié)果返回。
  //最后不要忘記在退出前釋放當前連接的上下文對象。
  redisFree(c);
  return;
}

int main() 
{
  doTest();
  return 0;
}

//輸出結(jié)果如下：
//Succeed to execute command[set stest1 value1].
//The length of 'stest1' is 6.
//Succeed to execute command[strlen stest1].
//The value of 'stest1' is value1.
//Succeed to execute command[get stest1].
//Succeed to execute command[get stest2].
//The value is value1.
//Succeed to execute command[mget stest1 stest2].
//Begin to test pipeline.
//Succeed to execute command[set stest1 value1] with Pipeline.
//Succeed to execute command[strlen stest1] with Pipeline.
//Succeed to execute command[get stest1] with Pipeline.
//Succeed to execute command[get stest2] with Pipeline.
//Succeed to execute command[mget stest1 stest2] with Pipeline.