一、前言
上一篇介紹了3種json解析工具的使用方法，對於基礎資料的解析沒有任何問題。
我們傳輸的json資料裡有unsigned long型資料，需要藉助json解析工具得到正確的unsigned long型資料。
本篇對比它們對64bit（8 byte）大整形資料的解析精度。
json樣本資料與上一篇一致，其中flow_id與key_id都是8 byte型大整數。

二、cjson解析精度測試

 1 #include "cJSON.h"
 2 
 3 #include <iostream>
 4 
 5 // g++ -g -o cjson_precision_test -std=c++11 precision_test.c cJSON.c
 

 6 
 7 using namespace std;
 8 
 9 int main()
10 {
11     cJSON *json_tmp;
12     cJSON *json_root;
13     
14     char str_buf[1024] = "{\"host\":\"www.baidu.com\",\"hostlen\":13,\"uagent\":\"curl/7.29.0\",\"accept\":\"*/*\",\"method\":\"GET\",\"date\":\"Mon, 12 Jul 21 10:35:26 GMT\",\"timestamp\":\"2021-07-12T02:38:13.074829000\",\"protocol_type\":\"http\",\"source_ip\":\"::112.1.101.40\",\"source_port\":22291,\"destination_ip\":\"::112.2.81.190\",\"destination_port\":80,\"flow_timestamp\":\"2021-07-12 02:38:13.074829000\",\"flow_id\":6996903014416199548,\"key_id\":7449212903698783717,\"token\":\"1556198765_129_1_8BFE1790A603B9C0067938B07CB5BB94B6926B81\"}
 
";
15 
16     json_root = cJSON_Parse(str_buf);
17 
18     json_tmp = cJSON_GetObjectItem(json_root, "flow_id");
19     if(NULL != json_tmp) {
20         cout << "flow_id:" << json_tmp->valueint << endl;
21         cout << "flow_id:" << json_tmp->valuedouble << endl;
 
22     }
23 
24     cJSON_Delete(json_root);
25     return 0;
26 }

執行結果：

三、rapidjson解析精度測試

 1 #include "rapidjson/document.h"
 2 #include "rapidjson/rapidjson.h"
 3 
 4 #include <iostream>
 5 
 6 // g++ -g -o rapidjson_precision_test -std=c++11 precision_test.c
 7 
 8 using namespace std;
 9 
10 int main()
11 {
12     char str_buf[1024] = "{\"host\":\"www.baidu.com\",\"hostlen\":13,\"uagent\":\"curl/7.29.0\",\"accept\":\"*/*\",\"method\":\"GET\",\"date\":\"Mon, 12 Jul 21 10:35:26 GMT\",\"timestamp\":\"2021-07-12T02:38:13.074829000\",\"protocol_type\":\"http\",\"source_ip\":\"::112.1.101.40\",\"source_port\":22291,\"destination_ip\":\"::112.2.81.190\",\"destination_port\":80,\"flow_timestamp\":\"2021-07-12 02:38:13.074829000\",\"flow_id\":6996903014416199548,\"key_id\":7449212903698783717,\"token\":\"1556198765_129_1_8BFE1790A603B9C0067938B07CB5BB94B6926B81\"}";
13 
14     rapidjson::Document parse_doc;
15     
16     parse_doc.Parse(str_buf);
17 
18     // 確定有flow_id場景，直接取值
19     cout << "flow_id:" << parse_doc.FindMember("flow_id")->value.GetUint64() << endl;
20 
21     return 0;
22 }

執行結果：

四、yyjson解析精度測試

 1 #include "yyjson.h"
 2 
 3 #include <iostream>
 4 
 5 // g++ -g -o yyjson_precision_test -std=c++11 precision_test.c yyjson.c
 6 
 7 using namespace std;
 8 
 9 int main()
10 {
11     char str_buf[1024] = "{\"host\":\"www.baidu.com\",\"hostlen\":13,\"uagent\":\"curl/7.29.0\",\"accept\":\"*/*\",\"method\":\"GET\",\"date\":\"Mon, 12 Jul 21 10:35:26 GMT\",\"timestamp\":\"2021-07-12T02:38:13.074829000\",\"protocol_type\":\"http\",\"source_ip\":\"::112.1.101.40\",\"source_port\":22291,\"destination_ip\":\"::112.2.81.190\",\"destination_port\":80,\"flow_timestamp\":\"2021-07-12 02:38:13.074829000\",\"flow_id\":6996903014416199548,\"key_id\":7449212903698783717,\"token\":\"1556198765_129_1_8BFE1790A603B9C0067938B07CB5BB94B6926B81\"}";
12     
13     yyjson_doc *doc;
14     yyjson_val *root;
15 
16     doc  = yyjson_read(str_buf, strlen(str_buf), 0);
17     root = yyjson_doc_get_root(doc);
18 
19     // 確定有flow_id場景，直接取值
20     cout << "flow_id:" << yyjson_get_uint(yyjson_obj_get(root, "flow_id")) << endl;
21 
22     return 0;
23 }

執行結果：