Parsing a text file C++ from specific line to specific line - c++

Question

so, I`m new to c++. My task is parse text file that look like:
RE002%%
RE002%%
RE002%%
RE002%%
RE002%%
RE004%on%
$GPGGA,124749.80,5543.3227107,N,03739.1366738,E,1,08,1.11,147.9635,M,14.4298,M,,*5C
$GPGSV,3,1,10,27,13,078,43,05,31,307,48,16,24,042,43,02,10,267,43*7D
$GPGSV,3,2,10,26,03,031,36,07,75,215,51,09,57,121,53,30,40,234,50*76
$GPGSV,3,3,10,23,29,117,46,04,36,114,46*70
$GPGGA,124749.90,5543.3227105,N,03739.1366737,E,1,08,1.11,147.9664,M,14.4298,M,,*54
RE005%off%
And it continuous for few thousand lines.I need to find where it writes RE004%on% and start processing lines in this loop until it finds RE005%off% and do it over and over until it file ends. I was trying to do it with line.find, but I am pretty sure it is wrong way to solve this problem
#include <iostream>
#include <fstream>
#include <string>
#include <stdlib.h>
using namespace std;
int main() {
string line, dollar, star, Checksum;
float *t0 = NULL;
int tount = 0;
int k;
ifstream logs_("C:/Users/Olya/Desktop/LogGLO.txt");
ofstream tout("outLOGTime.txt");
ofstream pout("outLOGPot.txt");
if (logs_.is_open())
{
while(getline(logs_,line))
{
line.find("RE004%on%")
k = 0;
if
dollar = line.find_first_of('$');
star = line.find_first_of('*');
Checksum = line.substr(line, dollar, star - dollar);
for (size_t i = 0; i < Checksum.size(); i++)
{
}
if (line.substr(0,6) == "$GPGSV")
{
for (size_t i = 0, N = 7; i < line.size(); i++)
{
if (line[i] == ',') k++;
if(k == N)
{
pout << line.substr(i+1,2) << endl;
if ((N += 4) > 19) break;
}
}
}
logs_.close();
}
}
else
cout<<"File is not open"<<'\n';
tout.close();
pout.close();
return 0;
}

Answer 1

Unfortunately your description si very unclear. Also by reading your code, I can really not understand, what you intent to do. And you edited your text and changed description. Not so easy for me
But, I made an educated guess. . .
I read all data between your given delimiters, validate the checksum and split the lines into tokens. Finally I store all the lines-with-Tokens in a vector. Then I filter for a specific value and output a column.
Please stude and try to understand. It is not so complicated.
Thank you
#include <iostream>
#include <regex>
#include <vector>
#include <iterator>
#include <string>
#include <utility>
#include <algorithm>
#include <functional>
#include <numeric>
#include <fstream>
const std::regex re{ R"(\$(.*)\*[abcdefABCDEF\d]{2})" };
const std::regex delimiter{ "," };
using Tokens = std::vector<std::string>;
std::tuple<bool, Tokens> checkString(const std::string& str) {
// Return value of the function. Assume that string is not ok
std::tuple<bool, std::vector<std::string>> result(false, {});
// We want to find a string in the given format
std::smatch sm{};
if (std::regex_match(str, sm, re)) {
// OK, found. Validate checksum
if (std::string s = sm[1];std::stoul(str.substr(str.size() - 2), nullptr, 16) == std::accumulate(s.begin(), s.end(), 0U, std::bit_xor<unsigned char>())) {
// Tokenize string
Tokens tokens(std::sregex_token_iterator(str.begin(), str.end(), delimiter, -1), {});
// Build return value
result = std::make_tuple(true, std::move(tokens));
}
}
return result;
}
int main() {
std::vector<Tokens> csvData{};
// Open file and check if it is open
if (std::ifstream logs("r:\\LogGLO.txt"); logs) {
// Shall we process text lines or not
bool processingActive{ false };
// Read all lines of files
for (std::string line{}; std::getline(logs, line);) {
// Check, if we should start or stio processing of the lines
if (line.substr(0, 9) == std::string("RE004%on%")) processingActive = true;
if (line.substr(0, 10) == std::string("RE005%off%")) processingActive = false;
// Check and read csv data
if (processingActive) {
const auto [ok, data] = checkString(line);
if (ok) csvData.push_back(std::move(data));
}
}
}
// So, now we have read all csv data
// Show eight column of GPGSV data
for (const Tokens& t : csvData)
if (t[0] == "$GPGSV")
std::cout << t[7] << "\n";
return 0;
}