docs:modify c example code

docs/zh/07-develop/07-tmq.md

@@ -54,7 +54,7 @@ DLL_EXPORT void           tmq_conf_destroy(tmq_conf_t *conf);
 DLL_EXPORT void           tmq_conf_set_auto_commit_cb(tmq_conf_t *conf, tmq_commit_cb *cb, void *param);
 ```
 
-这些 API 的文档请见 [C/C++ Connector](/reference/connector/cpp)，下面介绍一下它们的具体用法（超级表和子表结构请参考“数据建模”一节），完整的示例代码可以在 [tmq.c](https://github.com/taosdata/TDengine/blob/3.0/examples/c/tmq.c) 看到。
+这些 API 的文档请见 [C/C++ Connector](/reference/connector/cpp)，下面介绍一下它们的具体用法（超级表和子表结构请参考“数据建模”一节），完整的示例代码请见下面C语言的示例代码。
 
 ## 写入数据
 
@@ -65,13 +65,9 @@ drop database if exists tmqdb;
 create database tmqdb;
 create table tmqdb.stb (ts timestamp, c1 int, c2 float, c3 varchar(16) tags(t1 int, t3 varchar(16));
 create table tmqdb.ctb0 using tmqdb.stb tags(0, "subtable0");
-create table tmqdb.ctb1 using tmqdb.stb tags(1, "subtable1");
-create table tmqdb.ctb2 using tmqdb.stb tags(2, "subtable2");
-create table tmqdb.ctb3 using tmqdb.stb tags(3, "subtable3");       
+create table tmqdb.ctb1 using tmqdb.stb tags(1, "subtable1");       
 insert into tmqdb.ctb0 values(now, 0, 0, 'a0')(now+1s, 0, 0, 'a00');
 insert into tmqdb.ctb1 values(now, 1, 1, 'a1')(now+1s, 11, 11, 'a11');
-insert into tmqdb.ctb2 values(now, 2, 2, 'a1')(now+1s, 22, 22, 'a22');
-insert into tmqdb.ctb3 values(now, 3, 3, 'a1')(now+1s, 33, 33, 'a33');
 ```
 
 ## 创建topic：
@@ -133,7 +129,6 @@ TMQ支持多种订阅类型：
 
   tmq_t* tmq = tmq_consumer_new(conf, NULL, 0);
   tmq_conf_destroy(conf);
-  return tmq;
 ```
 
 上述配置中包括consumer group ID，如果多个 consumer 指定的 consumer group ID一样，则自动形成一个consumer group，共享消费进度。
@@ -146,66 +141,23 @@ TMQ支持多种订阅类型：
 ```sql
   tmq_list_t* topicList = tmq_list_new();
   tmq_list_append(topicList, "topicName");
-  return topicList;
 ```
 
 ## 启动订阅并开始消费
 
-```sql
+```
   /* 启动订阅 */
   tmq_subscribe(tmq, topicList);
   tmq_list_destroy(topicList);
   
   /* 循环poll消息 */
-  int32_t totalRows = 0;
-  int32_t msgCnt = 0;
-  int32_t timeOut = 5000;
   while (running) {
     TAOS_RES* tmqmsg = tmq_consumer_poll(tmq, timeOut);
-    if (tmqmsg) {
-      msgCnt++;
-      totalRows += msg_process(tmqmsg);
-      taos_free_result(tmqmsg);
-    } else {
-      break;
-	}
-  }
-  
-  fprintf(stderr, "%d msg consumed, include %d rows\n", msgCnt, totalRows);
+    msg_process(tmqmsg);
+  }  
 ```
 
-这里是一个 **while** 循环，每调用一次tmq_consumer_poll()，获取一个消息，该消息与普通查询返回的结果集完全相同，可以使用相同的解析API完成消息内容的解析：
-
-```sql
- static int32_t msg_process(TAOS_RES* msg) {
-  char buf[1024];
-  int32_t rows = 0;
-
-  const char* topicName = tmq_get_topic_name(msg);
-  const char* dbName    = tmq_get_db_name(msg);
-  int32_t     vgroupId  = tmq_get_vgroup_id(msg);
-
-  printf("topic: %s\n", topicName);
-  printf("db: %s\n", dbName);
-  printf("vgroup id: %d\n", vgroupId);
-
-  while (1) {
-    TAOS_ROW row = taos_fetch_row(msg);
-    if (row == NULL) break;
-
-    TAOS_FIELD* fields      = taos_fetch_fields(msg);
-    int32_t     numOfFields = taos_field_count(msg);
-    int32_t*    length      = taos_fetch_lengths(msg);
-    int32_t     precision   = taos_result_precision(msg);
-    const char* tbName      = tmq_get_table_name(msg);
-    rows++; 
-    taos_print_row(buf, row, fields, numOfFields);
-    printf("row content from %s: %s\n", (tbName != NULL ? tbName : "null table"), buf);
-  }
-
-  return rows;
-}
-```
+这里是一个 **while** 循环，每调用一次tmq_consumer_poll()，获取一个消息，该消息与普通查询返回的结果集完全相同，可以使用相同的解析API完成消息内容的解析。
 
 ## 结束消费
 
@@ -252,7 +204,285 @@ TMQ支持多种订阅类型：
 
 <Tabs>
 <TabItem label="C" value="c">
-TODO
+
+// A simple demo for asynchronous subscription.
+// compile with:
+// gcc -o tmq tmq.c -ltaos
+
+
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "taos.h"
+
+static int  running = 1;
+static char dbName[64] = "tmqdb";
+static char stbName[64] = "stb";
+static char topicName[64] = "topicname";
+
+static int32_t msg_process(TAOS_RES* msg) {
+  char    buf[1024];
+  int32_t rows = 0;
+
+  const char* topicName = tmq_get_topic_name(msg);
+  const char* dbName = tmq_get_db_name(msg);
+  int32_t     vgroupId = tmq_get_vgroup_id(msg);
+
+  printf("topic: %s\n", topicName);
+  printf("db: %s\n", dbName);
+  printf("vgroup id: %d\n", vgroupId);
+
+  while (1) {
+    TAOS_ROW row = taos_fetch_row(msg);
+    if (row == NULL) break;
+
+    TAOS_FIELD* fields = taos_fetch_fields(msg);
+    int32_t     numOfFields = taos_field_count(msg);
+    int32_t*    length = taos_fetch_lengths(msg);
+    int32_t     precision = taos_result_precision(msg);
+    const char* tbName = tmq_get_table_name(msg);
+    rows++;
+    taos_print_row(buf, row, fields, numOfFields);
+    printf("row content from %s: %s\n", (tbName != NULL ? tbName : "table null"), buf);
+  }
+
+  return rows;
+}
+
+static int32_t init_env() {
+  TAOS* pConn = taos_connect("localhost", "root", "taosdata", NULL, 0);
+  if (pConn == NULL) {
+    return -1;
+  }
+
+  TAOS_RES* pRes;
+  // drop database if exists
+  printf("create database\n");
+  pRes = taos_query(pConn, "drop database if exists tmqdb");
+  if (taos_errno(pRes) != 0) {
+    printf("error in drop tmqdb, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  // create database
+  pRes = taos_query(pConn, "create database tmqdb");
+  if (taos_errno(pRes) != 0) {
+    printf("error in create tmqdb, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  // create super table
+  printf("create super table\n");
+  pRes = taos_query(
+      pConn, "create table tmqdb.stb (ts timestamp, c1 int, c2 float, c3 varchar(16)) tags(t1 int, t3 varchar(16))");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to create super table stb, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  // create sub tables
+  printf("create sub tables\n");
+  pRes = taos_query(pConn, "create table tmqdb.ctb0 using tmqdb.stb tags(0, 'subtable0')");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to create super table ctb0, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  pRes = taos_query(pConn, "create table tmqdb.ctb1 using tmqdb.stb tags(1, 'subtable1')");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to create super table ctb1, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  pRes = taos_query(pConn, "create table tmqdb.ctb2 using tmqdb.stb tags(2, 'subtable2')");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to create super table ctb2, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  pRes = taos_query(pConn, "create table tmqdb.ctb3 using tmqdb.stb tags(3, 'subtable3')");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to create super table ctb3, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  // insert data
+  printf("insert data into sub tables\n");
+  pRes = taos_query(pConn, "insert into tmqdb.ctb0 values(now, 0, 0, 'a0')(now+1s, 0, 0, 'a00')");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to insert into ctb0, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  pRes = taos_query(pConn, "insert into tmqdb.ctb1 values(now, 1, 1, 'a1')(now+1s, 11, 11, 'a11')");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to insert into ctb0, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  pRes = taos_query(pConn, "insert into tmqdb.ctb2 values(now, 2, 2, 'a1')(now+1s, 22, 22, 'a22')");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to insert into ctb0, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  pRes = taos_query(pConn, "insert into tmqdb.ctb3 values(now, 3, 3, 'a1')(now+1s, 33, 33, 'a33')");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to insert into ctb0, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  taos_close(pConn);
+  return 0;
+}
+
+int32_t create_topic() {
+  printf("create topic\n");
+  TAOS_RES* pRes;
+  TAOS*     pConn = taos_connect("localhost", "root", "taosdata", NULL, 0);
+  if (pConn == NULL) {
+    return -1;
+  }
+
+  pRes = taos_query(pConn, "use tmqdb");
+  if (taos_errno(pRes) != 0) {
+    printf("error in use tmqdb, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  pRes = taos_query(pConn, "create topic topicname as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1");
+  if (taos_errno(pRes) != 0) {
+    printf("failed to create topic topicname, reason:%s\n", taos_errstr(pRes));
+    return -1;
+  }
+  taos_free_result(pRes);
+
+  taos_close(pConn);
+  return 0;
+}
+
+void tmq_commit_cb_print(tmq_t* tmq, int32_t code, void* param) {
+  printf("tmq_commit_cb_print() code: %d, tmq: %p, param: %p\n", code, tmq, param);
+}
+
+tmq_t* build_consumer() {
+  tmq_conf_res_t code;
+  tmq_conf_t*    conf = tmq_conf_new();
+  code = tmq_conf_set(conf, "enable.auto.commit", "true");
+  if (TMQ_CONF_OK != code) return NULL;
+  code = tmq_conf_set(conf, "auto.commit.interval.ms", "1000");
+  if (TMQ_CONF_OK != code) return NULL;
+  code = tmq_conf_set(conf, "group.id", "cgrpName");
+  if (TMQ_CONF_OK != code) return NULL;
+  code = tmq_conf_set(conf, "client.id", "user defined name");
+  if (TMQ_CONF_OK != code) return NULL;
+  code = tmq_conf_set(conf, "td.connect.user", "root");
+  if (TMQ_CONF_OK != code) return NULL;
+  code = tmq_conf_set(conf, "td.connect.pass", "taosdata");
+  if (TMQ_CONF_OK != code) return NULL;
+  code = tmq_conf_set(conf, "auto.offset.reset", "earliest");
+  if (TMQ_CONF_OK != code) return NULL;
+  code = tmq_conf_set(conf, "experimental.snapshot.enable", "true");
+  if (TMQ_CONF_OK != code) return NULL;
+  code = tmq_conf_set(conf, "msg.with.table.name", "true");
+  if (TMQ_CONF_OK != code) return NULL;
+
+  tmq_conf_set_auto_commit_cb(conf, tmq_commit_cb_print, NULL);
+
+  tmq_t* tmq = tmq_consumer_new(conf, NULL, 0);
+  tmq_conf_destroy(conf);
+  return tmq;
+}
+
+tmq_list_t* build_topic_list() {
+  tmq_list_t* topicList = tmq_list_new();
+  int32_t     code = tmq_list_append(topicList, "topicname");
+  if (code) {
+    return NULL;
+  }
+  return topicList;
+}
+
+void basic_consume_loop(tmq_t* tmq, tmq_list_t* topicList) {
+  int32_t code;
+
+  if ((code = tmq_subscribe(tmq, topicList))) {
+    fprintf(stderr, "%% Failed to tmq_subscribe(): %s\n", tmq_err2str(code));
+    return;
+  }
+
+  int32_t totalRows = 0;
+  int32_t msgCnt = 0;
+  int32_t timeout = 5000;
+  while (running) {
+    TAOS_RES* tmqmsg = tmq_consumer_poll(tmq, timeout);
+    if (tmqmsg) {
+      msgCnt++;
+      totalRows += msg_process(tmqmsg);
+      taos_free_result(tmqmsg);
+      /*} else {*/
+      /*break;*/
+    }
+  }
+
+  fprintf(stderr, "%d msg consumed, include %d rows\n", msgCnt, totalRows);
+}
+
+int main(int argc, char* argv[]) {
+  int32_t code;
+
+  if (init_env() < 0) {
+    return -1;
+  }
+
+  if (create_topic() < 0) {
+    return -1;
+  }
+
+  tmq_t* tmq = build_consumer();
+  if (NULL == tmq) {
+    fprintf(stderr, "%% build_consumer() fail!\n");
+    return -1;
+  }
+
+  tmq_list_t* topic_list = build_topic_list();
+  if (NULL == topic_list) {
+    return -1;
+  }
+
+  basic_consume_loop(tmq, topic_list);
+
+  code = tmq_unsubscribe(tmq);
+  if (code) {
+    fprintf(stderr, "%% Failed to unsubscribe: %s\n", tmq_err2str(code));
+  } else {
+    fprintf(stderr, "%% unsubscribe\n");
+  }
+
+  code = tmq_consumer_close(tmq);
+  if (code) {
+    fprintf(stderr, "%% Failed to close consumer: %s\n", tmq_err2str(code));
+  } else {
+    fprintf(stderr, "%% Consumer closed\n");
+  }
+
+  return 0;
+}
 </TabItem>
 
 <TabItem label="Java" value="java">