remove the last occurrence of character in string in file c++ - c++

Question

I have a function which reads each line in a file (using ifstream), modifies that line and then writes to a file with many "{key,value}," (by using fstream), I need to remove the last comma in that file, but after searching, I still have no idea to do this.
Does anyone have any suggestion please ?
current output file:
//bein file
std::map <std::string, std::string> my_map =
...
{key,value},
{key,value},
{last_key,last_value},
};
//some comment
expected output(remove the last comma):
//bein file
std::map <std::string, std::string> my_map =
...
{key,value},
{key,value},
{last_key,last_value}
};
//some comment
my code is here:
#include <windows.h>
#include <queue>
#include <string>
#include <iostream>
#include <regex>
#include <fstream>
#include <iterator>
#include <stdio.h>
// I think MS's names for some things are obnoxious.
const HANDLE HNULL = INVALID_HANDLE_VALUE;
const int A_DIR = FILE_ATTRIBUTE_DIRECTORY;
std::string write_cpp_file(std::string path, std::string line, std::string file_name)
{
std::string result = "output\\values.cpp";
if (path.find("values-en-rGB") != std::string::npos) {
std::fstream file("./output/result.cpp", std::ios::out | std::ios::app);
if (file)
{
file << line << std::endl;
file.close();
}
}
return result;
}
void analyze_file(std::string const &path, WIN32_FIND_DATA const &file) {
//std::cout << "path: " << path << "\n";
//std::cout << "file name: " << file.cFileName << "\n";
std::string file_name = path+file.cFileName;
std::cout << "processing file: " << file_name << "\n";
std::ifstream empSalariesOld(file_name);
//ofstream empSalariesNew("EmpSalariesNew.txt");
if (empSalariesOld)
{
std::string line;
std::regex open_comment("(.*)(<!--)(.*)");
std::regex close_comment("(.*)(-->)(.*)");
std::regex string_tag("(.*)(<string name=)(.*)");
std::regex find1("<string name=");
std::string replace1 = "{";
std::regex find2("\">");
std::string replace2 = "\",\"";
std::regex find3("</string>");
std::string replace3 = "\"},";
std::string result;
while (getline(empSalariesOld, line))
{
if (!std::regex_match(line, open_comment) &&
!std::regex_match(line, close_comment) &&
std::regex_match(line, string_tag) )
{
result = std::regex_replace(line, find1, replace1);
result = std::regex_replace(result, find2, replace2);
result = std::regex_replace(result, find3, replace3);
std::string cpp_file = write_cpp_file(path, result, file_name);
}
}
}
empSalariesOld.close();
//empSalariesNew.close();
}
//process each file in folder/subfolder
void convert(std::string const &folder_name) {
HANDLE finder; // for FindFirstFile
WIN32_FIND_DATA file; // data about current file.
std::priority_queue<std::string, std::vector<std::string>,
std::greater<std::string> > dirs;
dirs.push(folder_name); // start with passed directory
do {
std::string path = dirs.top();// retrieve directory to search
dirs.pop();
if (path[path.size()-1] != '\\') // normalize the name.
path += "\\";
std::string mask = path + "*"; // create mask for searching
// traverse a directory. Search for sub-dirs separately, because we
// don't want a mask to apply to directory names. "*.cpp" should find
// "a\b.cpp", even though "a" doesn't match "*.cpp".
//
// First search for files:
if (HNULL==(finder=FindFirstFile(mask.c_str(), &file)))
continue;
do {
if (!(file.dwFileAttributes & A_DIR))
analyze_file(path, file);
} while (FindNextFile(finder, &file));
FindClose(finder);
// Then search for subdirectories:
if (HNULL==(finder=FindFirstFile((path + "*").c_str(), &file)))
continue;
do {
if ((file.dwFileAttributes & A_DIR) && (file.cFileName[0] != '.'))
dirs.push(path + file.cFileName);
} while (FindNextFile(finder, &file));
FindClose(finder);
} while (!dirs.empty());
}
void create_output_folder()
{
std::string command = "del /Q ";
std::string path = "output\\*.cpp";
system(command.append(path).c_str());
CreateDirectory("output", NULL);
}
int main()
{
create_output_folder();
convert("./Strings");
std::cout << "finish convert" << "\n";
return 0;
}

Answer 1

You can do the following do a first write to file without any , outside the loop. Then for the others write inside the loop you print the , at the beginning of the line:
if (getline(empSalariesOld, line))
{
if (!std::regex_match(line, open_comment) &&
!std::regex_match(line, close_comment) &&
std::regex_match(line, string_tag) )
{
result = std::regex_replace(line, find1, replace1);
result = std::regex_replace(result, find2, replace2);
result = std::regex_replace(result, find3, replace3);
//remove the first char which is the comma
result = result.substr(1, result.size()-1)
std::string cpp_file = write_cpp_file(path, result, file_name);
}
}
while (getline(empSalariesOld, line))
{
if (!std::regex_match(line, open_comment) &&
!std::regex_match(line, close_comment) &&
std::regex_match(line, string_tag) )
{
result = std::regex_replace(line, find1, replace1);
result = std::regex_replace(result, find2, replace2);
result = std::regex_replace(result, find3, replace3);
std::string cpp_file = write_cpp_file(path, result, file_name);
}
}
I am guessing you are putting the comma in replace3. You can:
std::string replace1 = ",\n{"; \\put the comma at beginning of line then got to the next line
...
std::string replace3 = "\"}"
And since you are putting the new line in replace1 you should remove it from new file:
file << line;