formatting flattened string into JSON-like object in C++

Question

I have a string which contains JSON-like object flattened (stringify()ed).

I need to JSON-ify it back. It's a custom format, so I wrote function to JSON-ify the string:

#include <string>
#include <unordered_set>
#include <iostream>

const std::unordered_set<std::string> reservedWords{ "coords", "comment" };

std::string jsonify(const std::string &tclString)
{
    std::string result;

    int level = 0;
    const int tabWidth = 4;

    bool reservedWord = false;
    const auto length = tclString.length();
    std::string prevWord;
    for (auto idx = 0; idx < length; ++idx)
    {
        auto ch = tclString[idx];
        if (ch == ' ')
            result += ' ';
        else if (ch == '{')
        {
            std::string word;
            while (++idx < length)
            {
                ch = tclString[idx];
                if (ch == ' ' || ch == '}')
                    break;
                word += ch;
            }

            result += '{';
            if (word == "}")
            {
                if (reservedWord)
                    reservedWord = false;
            }
            else if (!reservedWord)
            {
                ++level;
                result += '\n';
                result += std::string(level * tabWidth, ' ');
                reservedWord = reservedWords.contains(word);
            }

            --idx;
            result += word;
        }
        else if (ch == '}')
        {
            if (reservedWord)
            {
                result += '}';
                reservedWord = false;
            }
            else
            {
                --level;
                result += '\n';
                result += std::string(level * tabWidth, ' ');
                result += '}';
                result += '\n';
            }
        }
        else
        {
            std::string word;
            while (idx < length)
            {
                if (ch == '}' || ch == ' ' || ch == '{')
                    break;
                word += ch;
                ++idx;
                ch = tclString[idx];
            }
            --idx;
            result += word;
            if (!reservedWord)
                reservedWord = reservedWords.contains(word);
        }
    }

    return result;
}

int main()
{
    std::cout << jsonify("{data {a {obj {coords {10 10} comment {} radius 260 type circle}}}}") << '\n';
    std::cout << jsonify("{data {b {obj {coords {-95 -85 -70 -85 -75 -95} comment {abc} type polygon}}}}") << '\n';
    std::cout << jsonify("{data {c {obj {coords {-55 -65 -70 -65 -25 -64} comment {abc def} type polygon}}}}") << '\n';
}

Please review the code and let me know how I can make it better?

Thanks in advance.

Toby Speight · Accepted Answer · 2022-01-27 08:15:51Z

1

All the functionality is written in one fat function, which prevents modularization of code. Try to break up it into subfunctions; you could separate:
```
    std::string word;
    while (++idx < length)
    {
        ch = tclString[idx];
        if (ch == ' ' || ch == '}')
            break;
        word += ch;
    }
```
This is simply trying to tokenize the input into words. You could do that in another function.
I see repetitions of similar logic for tokenizing in the else part, albeit with minor modification; you could try and club it into one function and pass separators.
I think the case is more suited for a while loop, then you don't have to spray around the:
```
--idx
```
The variable
```
std::string prevWord
```
is not used at all.
Overall, the design is not flexible enough and does not incorporate OCP. If you had to accommodate any change you would be changing the function. Consider using something like a fluent builder pattern here. Depending upon how complex it is you can think of using javax.json.

edited Jan 27, 2022 at 8:15

Toby Speight

88.4k14 gold badges104 silver badges327 bronze badges

answered Jan 27, 2022 at 5:30

Suryasis Paul

4583 silver badges9 bronze badges

\$\begingroup\$ Can you expand the acronym OCP and perhaps provide a link to its definition? Also a link to a description of the "fluent builder pattern" would help. \$\endgroup\$

G. Sliepen
– G. Sliepen

2022-01-27 22:59:45 +00:00
Commented Jan 27, 2022 at 22:59
\$\begingroup\$ @Suryasis Paul thanks for the feedback. I have updated the code in new post: codereview.stackexchange.com/questions/273552/…. can you please take a look again? \$\endgroup\$

user3132457
– user3132457

2022-01-30 18:01:55 +00:00
Commented Jan 30, 2022 at 18:01

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