How to match if file paths already present in the txt file before writing to the same txt file

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I have a function that searches through directory and then writes the path of the files in a text file
now what i want to do is that i need to match if during search files that are retrieved already present in this text file if not present then append them in the end of that text file otherwise if it matches with the path of the file that re already present then ignore them and don't write it to the file
this is my function

Now i know i can use eof to get files from text file and then match them with the path I have retreived but i cannot think of any logic

What I have tried:

I thought of this but it only matches the first line of text file and after matching it doesnt write but after that getfil function currFile doesn't change so it doesn't work

string str;
					do {
						while (getline(read, str))
						{
							if (str != currFile)
							{	//if(()
								file <</*counter<<"-"<< */"\n"<<currFile << endl;
								counter++;

							}
							else if (str == currFile)
							{
								break;
							}
							break;

						}
					} while (!read.eof());

Posted 18-Feb-20 22:18pm

Member 12899279

Updated 19-Feb-20 18:14pm

v3

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CPallini · Answer 1 · 2020-02-18T22:47:00

Solution 1

Use a std::set Luke, use a std::set!

Use the set to store the path of already found files (the ones present in your txt file).
Then, during search, insert the found files in the same set.
Eventually store the set content into the original txt file (overwriting it).

Posted 18-Feb-20 22:47pm

CPallini

Comments

Member 12899279 19-Feb-20 11:43am

got it working with using vector now searching time is increased significantly is there any better approach that would minimize the time search?

CPallini 19-Feb-20 13:30pm

Try to use the std::set, instead.

Member 12899279 19-Feb-20 23:14pm

reason?

CPallini 20-Feb-20 3:46am

Because you don't have to check for duplicates, that's automatically handled by the data structure itself.

Member 12899279 20-Feb-20 9:46am

yes i read about it but if we consider speed then vector is considerably better

Richard MacCutchan · Answer 2 · 2020-02-18T23:34:00

Lots of redundant code in there:

C++

int getfil(void *args) // why are you using void* and not char* ?
{
    char *tmpPath = (char *)args; // why not just use the input argument ?
    string sPath(tmpPath);
    WIN32_FIND_DATA FindFileData;
    string sTmpPath = sPath; // why are you creating a copy of sPath ?
    sTmpPath += "\\*.*";

C++

// a neater way ...
int getfil(char *sourcePath)
{
    WIN32_FIND_DATA FindFileData;
    string sTmpPath = sourcePath;
    sTmpPath += "\\*.*";

k5054 · Answer 3 · 2020-02-18T22:58:00

This sounds like a place to use a std::set - cppreference.com[^] You need to look through the whole file for matches anyway, so why not read the entire file at the beginning of you program, putting each line into a std::set<string>. Then as you find your matches, call find(). If it returns end(), then you know its not in the set, so you need add the filename to the file of already matched files. Unless you think there's a good chance your disk search algorithm will find the same file multiple times, you don't need to add the file to the set.

If you don't need to append the file name right away, that is, the file update can wait until you've finished the scan, and it is not important that the text file be in order that the matches were found, then all you need to do is every time you find a match, justinsert() the filename into the set. When you're done your scan, rewind the text file and write out the entire set. This will give the added benefit that the text file will always be in sorted order.

If the text file is just working as a database, and doesn't ever need to be read by a human, then maybe consider using a key/value store.

How to match if file paths already present in the txt file before writing to the same txt file

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