我需要用 C 決議日志檔案。我有這個檔案中的這個字串樣本：
[2020-08-23 19:19:29.137] [exchange_tools] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212350,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187624,"prev_seq_num": 111529187575,"asks": [],"bids": [[11666.14, 6.752865]]}
從這個 JSON 我需要：“type”、“event_time”、“asks”、“bids”。
我目前的解決方案是：對于檔案中的每個字串，洗掉 python 上從開始到“物件：”的第一個符號。
{"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212350,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187624,"prev_seq_num": 111529187575,"asks": [],"bids": [[11666.14, 6.752865]]}
然后我保存就像 JSON 檔案一樣，讀取 C 中的每個字串：
boost::property_tree::ptree pt;
std::ifstream json_in("outfile.json");
std::string line_json;
while (std::getline(json_in, line_json)) {
std::stringstream ss;
ss << line_json;
boost::property_tree::read_json(ss, pt);
std::cout << pt.get<std::string>("type") << std::endl;
}
它對我有用，但我想在不使用 python 的情況下決議 C （boost）中的日志檔案。我該怎么做？
uj5u.com熱心網友回復：
首先，不要誤用屬性樹來支持 JSON 或 XML。請改用 Boost JSON。
其次，當然您可以在 C 中進行字串操作。這是一個應該易于擴展的示例：
#include <boost/fusion/adapted/struct.hpp>
#include <boost/iostreams/device/mapped_file.hpp>
#include <boost/spirit/home/x3.hpp>
struct Record {
std::string time, source, level, msg;
};
using Records = std::vector<Record>;
BOOST_FUSION_ADAPT_STRUCT(Record, time, source, level, msg)
namespace Parser {
using namespace boost::spirit::x3;
auto bracketed = rule<struct _, std::string>{"bracketed"}
= '[' >> raw[*~char_(']')] >> ']';
auto time = bracketed; // perhaps refine
auto source = bracketed; // perhaps refine
auto level = bracketed; // perhaps refine
auto msg = lexeme[*(char_ - eol)]; // perhaps refine
auto record = rule<struct record, Record>{"record"}
= time >> source >> level >> msg;
auto records = *(record >> ( eol | eoi));
auto file = skip(blank)[records] >> eoi;
} // namespace Parser
Records ParseRecords(std::string const& fname) {
Records records;
boost::iostreams::mapped_file_source file(fname);
if (!parse(file.begin(), file.end(), Parser::file, records))
throw std::runtime_error("Parsing failed\n");
return records;
}
#include <boost/json/src.hpp> // for header-only
#include <iostream>
namespace json = boost::json;
int main() {
for (auto& r : ParseRecords("input.txt")) {
std::string_view payload = r.msg;
if (payload.starts_with("Get Object: ")) {
auto obj = json::parse(payload.substr(12));
std::cout << " -----\n"
<< " Level: " << r.level << "\n"
<< " Time: " << r.time << "\n"
<< " Source: " << r.source << "\n"
<< " Type: " << obj.at("type") << "\n"
<< " Event Time: " << obj.at("event_time") << "\n"
<< " Asks: " << obj.at("asks") << "\n"
<< " Bids: " << obj.at("bids") << "\n";
}
}
}
對于input.txt：
[2020-08-23 19:19:29.137] [exchange_tools] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212350,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187624,"prev_seq_num": 111529187623,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:30.137] [exchange_fools] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212351,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187625,"prev_seq_num": 111529187624,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:31.137] [exchange_pools] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212352,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187626,"prev_seq_num": 111529187625,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:32.137] [exchange_mules] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212353,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187627,"prev_seq_num": 111529187626,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:33.137] [exchange_rulez] [info] Put Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212354,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187628,"prev_seq_num": 111529187627,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:34.137] [exchange_bools] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212355,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187629,"prev_seq_num": 111529187628,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:35.137] [exchange_cools] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212356,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187630,"prev_seq_num": 111529187629,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:36.137] [exchange_solos] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212357,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187631,"prev_seq_num": 111529187630,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:37.137] [exchange_rolos] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212358,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187632,"prev_seq_num": 111529187631,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:38.137] [exchange_sucks] [info] Fudge Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212359,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187633,"prev_seq_num": 111529187632,"asks": [],"bids": [[11666.14, 6.752865]]}
[2020-08-23 19:19:39.137] [exchange_rocks] [info] Get Object: {"type": "update","symbol": "BTC_USDT_20l","event_id": 1598210353212360,"event_time": 1598210365978240,"exchange_time": 1598210365818,"seq_num": 111529187634,"prev_seq_num": 111529187633,"asks": [],"bids": [[11666.14, 6.752865]]}
列印預期的輸出：
-----
Level: info
Time: 2020-08-23 19:19:29.137
Source: exchange_tools
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
-----
Level: info
Time: 2020-08-23 19:19:30.137
Source: exchange_fools
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
-----
Level: info
Time: 2020-08-23 19:19:31.137
Source: exchange_pools
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
-----
Level: info
Time: 2020-08-23 19:19:32.137
Source: exchange_mules
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
-----
Level: info
Time: 2020-08-23 19:19:34.137
Source: exchange_bools
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
-----
Level: info
Time: 2020-08-23 19:19:35.137
Source: exchange_cools
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
-----
Level: info
Time: 2020-08-23 19:19:36.137
Source: exchange_solos
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
-----
Level: info
Time: 2020-08-23 19:19:37.137
Source: exchange_rolos
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
-----
Level: info
Time: 2020-08-23 19:19:39.137
Source: exchange_rocks
Type: "update"
Event Time: 1598210365978240
Asks: []
Bids: [[1.166614E4,6.752865E0]]
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