How can we modify the high score example to store multiple high scores (e.g., the top 10) instead of just one?

Question

Ryan McCombe · Accepted Answer

To store multiple high scores, you could use an array or a std::vector within your data file. For example, let's store the top 5 scores.

You'll need to decide how you want to handle the situation when the file doesn't exist or has fewer than 5 scores. One approach is to initialize the file with 5 default scores (e.g., 0) if it is newly created.

Updating the File Structure

First, let's update the code to handle an array of 5 integers instead of a single integer:

1#include <SDL.h>
2#include <algorithm>
3#include <iostream>
4
5void UpdateHighScore(
6  const char* Path, int32_t NewScore
7) {
8  // Open the file in "w+b" mode to create
9  // or update
10  SDL_RWops* File{SDL_RWFromFile(Path, "w+b")};
11  if (!File) {
12    std::cerr << "Error opening file: "
13      << SDL_GetError() << "\n";
14    return;
15  }
16
17  const int NumScores{5};
18  int32_t HighScores[NumScores];
19
20  // Read the current high scores from the file
21  size_t ScoresRead{SDL_RWread(
22    File, HighScores, sizeof(int32_t), NumScores
23  )};
24
25  // Initialize with default scores if fewer
26  // than NumScores were read
27  if (ScoresRead < NumScores) {
28    std::cout << "Initializing new high scores\n";
29    for (size_t i{ScoresRead}; i<NumScores; ++i) {
30      HighScores[i] = 0;
31    }
32  }
33
34  // Check if the new score is a high score
35  bool IsHighScore{false};
36  for (int i{0}; i < NumScores; ++i) {
37    if (NewScore > HighScores[i]) {
38      IsHighScore = true;
39      break;
40    }
41  }
42
43  if (IsHighScore) {
44    std::cout << NewScore << " is a new high "
45      "score! Updating file\n";
46
47    // Add the new score and sort
48    HighScores[NumScores - 1] = NewScore;
49    std::sort(
50      HighScores,
51      HighScores + NumScores,
52      std::greater<int32_t>()
53    );
54
55    // Rewind to the beginning of the file and
56    // write the updated scores
57    SDL_RWseek(File, 0, RW_SEEK_SET);
58    SDL_RWwrite(
59      File,
60      HighScores,
61      sizeof(int32_t),
62      NumScores
63    );
64  } else {
65    std::cout << "Not a high score - file "
66      "not updated\n";
67  }
68
69  SDL_RWclose(File);
70}
71
72int main() {
73  UpdateHighScore("highscores.dat", 5000);
74  UpdateHighScore("highscores.dat", 3000);
75  UpdateHighScore("highscores.dat", 6000);
76  UpdateHighScore("highscores.dat", 4000);
77  UpdateHighScore("highscores.dat", 2000);
78  UpdateHighScore("highscores.dat", 5500);
79  return 0;
80}

1Initializing new high scores
25000 is a new high score! Updating file
33000 is a new high score! Updating file
46000 is a new high score! Updating file
54000 is a new high score! Updating file
62000 is a new high score! Updating file
75500 is a new high score! Updating file

Explanation

We declare an array HighScores to hold the top 5 scores.
We attempt to read 5 scores from the file. If fewer are read (e.g., the file is new or incomplete), we initialize the remaining elements of HighScores to 0.
We check if the NewScore is greater than any of the current high scores.
If it is a high score, we add it to the array, sort the array in descending order using std::sort() and std::greater<>(), rewind to the beginning of the file, and write the updated scores. Note we have added an #include <algorithm> to support this change.
We print a message to inform the user if the score was not added to the top 5

Remember that this example assumes you always want to maintain a fixed number of high scores (5 in this case).

You could make the system more flexible by storing the number of scores at the beginning of the file, but that would add complexity.

Read/Write Offsets and Seeking

Multiple High Scores

Updating the File Structure

Explanation

Read/Write Offsets and Seeking

Game Development with SDL2

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