CODEWITHSUNDEEP
c++
user5988042
user5988042

Reputation:

Bug: Why does this getline only loop once?

while(getline(data, word, '\n')){//seperates by line
    ss<<word; // output1: Chicken, for sale, 60
              // output2: Microwave, wanted, 100 (and so on)

    while(getline(ss, word, ',')){//seperates by individual words + space
        // output1: Chicken
        // output2: for sale
        // output3: 60
        if(word[0]==' '){ //removes space in 2 and 3
            word.erase(0,1);
        }

        if(wordindex==0){
            board[i].object=word;
            wordindex++;
        }
        else if(wordindex==1){
            board[i].type=word;
            wordindex++;
        }
        else if(wordindex==2){
            board[i].price=word;
            wordindex=0; //resets index to 0 for next line
            i++; //moves to next struct in array
        }
    }
}

The second getline loop only loops once for the first input: chicken, for sale, and 60 and does not reach the second. I figure word index is always set to 0 so it shouldn't be a problem. Also, the first getline() outputs all data entirely, so something is causing the second getline() to get confused. I just can't see what it is.

Upvotes: 1

Views: 253

Answers (1)

user4581301
user4581301

Reputation: 33932

Here

ss<<word;

OP reuses a stringstream that may have been read to the end on a previous iteration, setting the stream into a bad state where it can no longer be written to or read from. This can be resolved by adding 

ss.clear();

at the end of the loop to remove any bad flags, but by constantly writing mor data into the stringstream it will continue to grow, soaking up more and more memory unless emptied out with something like

ss.str(std::string());

to set it's internal buffer back to an empty string. It might be better to just create a new stringstream each iteration just for code clarity if the added cost of construction and destruction to the parsing speed is not an issue.

Here is one simpler approach to the inner parsing loop:

std::stringstream ss(word);
while(i<MAX_ARRAY_SIZE && // prevent overflow
      getline(ss,  board[i].object, ',') && 
      getline(ss, board[i].type, ',') && 
      getline(ss, board[i].price, ',')){ // read all three parameters directly into object
    //sanitize
    if(board[i].type[0]==' '){ 
        board[i].type.erase(0,1);
    }

    if(board[i].price[0]==' '){ 
        board[i].price.erase(0,1);
    }
    i++; // next, please
}

Upvotes: 2

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