70 lines
2.5 KiB
Markdown
70 lines
2.5 KiB
Markdown
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# 字符串类型 KV 示例
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该示例主要演示了字符串 KV 的相关功能，字符串 KV 作为一个特殊的 KV 类型，其 Key 与 Value 均为字符串，常被用于参数存储、命令存储等可读性要求较高的场景。
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## 代码说明
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示例代码位于 `samples/kvdb_type_string.c` ，使用一个名为 `"temp"` 的 KV 来存储温度值，分别演示了字符串 KV 从 `创建->读取->修改->删除` 的全过程。大致内容如下：
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```C
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void kvdb_type_string_sample(fdb_kvdb_t kvdb)
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{
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FDB_INFO("==================== kvdb_type_string_sample ====================\n");
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{ /* CREATE new Key-Value */
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char temp_data[10] = "36C";
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/* It will create new KV node when "temp" KV not in database. */
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fdb_kv_set(kvdb, "temp", temp_data);
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FDB_INFO("create the 'temp' string KV, value is: %s\n", temp_data);
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}
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{ /* GET the KV value */
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char *return_value, temp_data[10] = { 0 };
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/* Get the "temp" KV value.
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* NOTE: The return value saved in fdb_kv_get's buffer. Please copy away as soon as possible.
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*/
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return_value = fdb_kv_get(kvdb, "temp");
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/* the return value is NULL when get the value failed */
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if (return_value != NULL) {
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strncpy(temp_data, return_value, sizeof(temp_data));
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FDB_INFO("get the 'temp' value is: %s\n", temp_data);
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}
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}
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{ /* CHANGE the KV value */
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char temp_data[10] = "38C";
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/* change the "temp" KV's value to "38.1" */
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fdb_kv_set(kvdb, "temp", temp_data);
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FDB_INFO("set 'temp' value to %s\n", temp_data);
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}
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{ /* DELETE the KV by name */
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fdb_kv_del(kvdb, "temp");
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FDB_INFO("delete the 'temp' finish\n");
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}
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FDB_INFO("===========================================================\n");
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}
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```
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## 运行日志
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通过日志可以看出：
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- 首先创建了一个 KV 名为 `"temp"` ，并给予初值 36℃
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- 读取 `"temp"` KV 当前的值，发现与初值相同
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- 修改 `"temp"` KV 的值为 38℃
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- 最后删除 `"temp"` KV
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```
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[FlashDB][sample][kvdb][string] ==================== kvdb_type_string_sample ====================
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[FlashDB][sample][kvdb][string] create the 'temp' string KV, value is: 36C
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[FlashDB][sample][kvdb][string] get the 'temp' value is: 36C
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[FlashDB][sample][kvdb][string] set 'temp' value to 38C
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[FlashDB][sample][kvdb][string] delete the 'temp' finish
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[FlashDB][sample][kvdb][string] ===========================================================
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```
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