Thread: Am I writing binary data correctly

I am having problems either writing data to a binary file or reading from the file. Through the process of elimination I am posting the code where the data is written to file to see if I can eliminate that as an option. I know the data is being processed correctly because, through the use of another function, I can view the data.

I also know that fwrite must be including some padding because the file size ends up being 576 bytes after it is written instead of 540 bytes (the size it would be if no padding is used).

Here is my struct:

Code:

typedef struct {
    char teams[25];
    float wins;
    float losses;
    float pct;
    int runsScored;
    int runsAgainst;
} STATISTICS;

Here is where I initialize it:

Code:

STATISTICS stats[12] =
        {
            {"Anaheim Arrays", 0.0, 0.0, .000, 0, 0},
            {"Pittsburg Pointers", 0.0, 0.0, .000, 0, 0},
            {"Indianapolis Integers", 0.0, 0.0, .000, 0, 0},
            {"Denver Double", 0.0, 0.0, .000, 0, 0},    
            {"Sacremento Strings", 0.0, 0.0, .000, 0, 0},
            {"Vancouver Vectors", 0.0, 0.0, .000, 0, 0},        
            {"Minnesota Mallocs", 0.0, 0.0, .000, 0, 0},
            {"Fargo Floats", 0.0, 0.0, .000, 0, 0},
            {"Chicago Callocs", 0.0, 0.0, .000, 0, 0},
            {"Dallas Delimeters", 0.0, 0.0, .000, 0, 0},
            {"San Diego Structs", 0.0, 0.0, .000, 0, 0},    
            {"Washington Destroyers", 0.0, 0.0, .000, 0, 0}
    };

and here is the function that writes my data. The sA array is only used to change the scheduled games based on the variable week.

Code:

void schedule(STATISTICS stats[]) { //http://www.crowsdarts.com/roundrobin/sched12.html
    FILE *f;
    int sA[12], week = 0, runsPerGameA = 0, runsPerGameB = 0, runsAgainstA = 0, runsAgainstB = 0;
    int index, a = 0, b = 1, i = 0;


    f = fopen("Cleague.bin", "wb");
    
    week = stats[0].wins + stats[0].losses + 1;
    
    switch (week) {
        case 1:
            sA[0]=0, sA[1]=1, sA[2]=2, sA[3]=3, sA[4]=4, sA[5]=5, sA[6]=6, sA[7]=7, sA[8]=8, sA[9]=9, sA[10]=10, sA[11]=11;
            break;            
        case 2:
            sA[0]=10, sA[1]=0, sA[2]=1, sA[3]=2, sA[4]=3, sA[5]=4, sA[6]=5, sA[7]=6, sA[8]=7, sA[9]=8, sA[10]=11, sA[11]=9;
            break;
        case 3:
            sA[0]=0, sA[1]=2, sA[2]=3, sA[3]=1, sA[4]=4, sA[5]=6, sA[6]=7, sA[7]=5, sA[8]=9, sA[9]=10, sA[10]=8, sA[11]=11;
            break;
        case 4:
            sA[0]=5, sA[1]=0, sA[2]=1, sA[3]=10, sA[4]=6, sA[5]=3, sA[6]=2, sA[7]=9, sA[8]=8, sA[9]=4, sA[10]=11, sA[11]=7;
            break;
        case 5:
            sA[0]=9, sA[1]=0, sA[2]=1, sA[3]=8, sA[4]=2, sA[5]=10, sA[6]=3, sA[7]=5, sA[8]=7, sA[9]=4, sA[10]=6, sA[11]=11;
            break;
        case 6:
            sA[0]=0, sA[1]=8, sA[2]=9, sA[3]=1, sA[4]=3, sA[5]=7, sA[6]=6, sA[7]=2, sA[8]=10, sA[9]=4, sA[10]=11, sA[11]=5;
            break;
        case 7:
            sA[0]=0, sA[1]=3, sA[2]=5, sA[3]=1, sA[4]=2, sA[5]=7, sA[6]=6, sA[7]=9, sA[8]=8, sA[9]=10, sA[10]=4, sA[11]=11;
            break;
        case 8:
            sA[0]=0, sA[1]=6, sA[2]=7, sA[3]=1, sA[4]=8, sA[5]=2, sA[6]=4, sA[7]=9, sA[8]=10, sA[9]=5, sA[10]=11, sA[11]=3;
            break;
        case 9:
            sA[0]=4, sA[1]=0, sA[2]=1, sA[3]=6, sA[4]=7, sA[5]=9, sA[6]=8, sA[7]=5, sA[8]=10, sA[9]=3, sA[10]=2, sA[11]=11;
            break;
        case 10:
            sA[0]=7, sA[1]=0, sA[2]=10, sA[3]=6, sA[4]=4, sA[5]=2, sA[6]=9, sA[7]=5, sA[8]=3, sA[9]=8, sA[10]=11, sA[11]=1;
            break;
        case 11:
            sA[0]=8, sA[1]=6, sA[2]=1, sA[3]=4, sA[4]=5, sA[5]=2, sA[6]=7, sA[7]=10, sA[8]=3, sA[9]=9, sA[10]=0, sA[11]=11;
            break;
        case 12:
            printf("\t\tThe Season is over. Here are the final standings\n");
            showStats(stats, -1);
            break;
            
    }
    printf("Please enter the results from the week %i games.\n\n\n", week);
    printf("The home team %s plays the visiting %s\n", stats[sA[0]].teams, stats[sA[1]].teams);
    printf("The home team %s plays the visiting %s\n", stats[sA[2]].teams, stats[sA[3]].teams);
    printf("The home team %s plays the visiting %s\n", stats[sA[4]].teams, stats[sA[5]].teams);
    printf("The home team %s plays the visiting %s\n", stats[sA[6]].teams, stats[sA[7]].teams);    
    printf("The home team %s plays the visiting %s\n", stats[sA[8]].teams, stats[sA[9]].teams);
    printf("The home team %s plays the visiting %s\n", stats[sA[10]].teams, stats[sA[11]].teams);
    pause;
    cls;
        
        
    for (index = 0; index < 6; index++){
        printf("Enter the runs scored for %s  :", stats[sA[a]].teams);
        scanf("%i", &runsPerGameA);
        printf("Enter the runs scored for %s: ", stats[sA[b]].teams);
        scanf("%i", &runsPerGameB);
        runsAgainstA = runsPerGameB;
        runsAgainstB = runsPerGameA;
    
        if (runsPerGameA  < runsPerGameB){
            stats[sA[a]].losses += 1;
            stats[sA[b]].wins += 1;
        }
        else {
            stats[sA[a]].wins += 1;
            stats[sA[b]].losses += 1;
            }
    
        stats[sA[a]].runsScored += runsPerGameA;
        stats[sA[b]].runsScored += runsPerGameB;
        stats[sA[a]].runsAgainst += runsAgainstA;
        stats[sA[b]].runsAgainst += runsAgainstB;
    
        if (stats[sA[a]].wins == 0){
            stats[sA[a]].pct = .000;
        }
        else {
            stats[sA[a]].pct = stats[sA[a]].wins / (stats[sA[a]].losses + stats[sA[a]].wins);
        }
    
        if (stats[sA[b]].wins == 0){
            stats[sA[b]].pct = .000;
        }
        else {
            stats[sA[b]].pct = stats[sA[b]].wins / (stats[sA[b]].losses + stats[sA[b]].wins);
        }
        a += 2;
        b += 2;
    }
    
    
    if (!f)
    {
        cls;
        printf("Unable to open file!");
        pause;
        exit (0);
    }
    for (i = 0; i < 12; i++){
        fwrite(&stats[i], sizeof(stats[i]), 1, f);
    }
    fclose(f);
}

Can someone tell me if this is where my problem lies or is it more likely at a different point in the program where I am reading from the file.

Thanks in advance,

Michael

Troubleshooting a problem dealing with reading and writing to a binary file is difficult. But in order to help, you will probably need to show your read function. And really a small test program that just writes and reads your structure would probably be best.

Jim

Thanks, here is the function that implements the fread portion. I also included the source file, in case anyone wanted to take a further look. As you notice, I did not include a file path but that is because it is easier for my instructor not to receive multiple different paths with each assignment.

Code:

void showStats(STATISTICS stats[], int finalize) {
    
    FILE *f;
    int i = 0, j, size = 12;
    f = fopen("Cleague.bin", "rb");
    
    if (f==NULL){
        perror("error");
    }
    
    while(fread(&stats[i], sizeof(stats[i]), 1, f) > 0){    
            i++;                                                
        }                                            
    
    for (i = 0; i < size-1; i++) {
      int max = i;
        for (j = i+1; j < size; j++) {
            if (stats[j].pct > stats[max].pct) {
                max = j;
            }
        }
        if (max != i) { // if you're not changing position, don't swap
            STATISTICS temp = stats[i];
            stats[i] = stats[max];
            stats[max] = temp;
        }
    }


    
    i = 0;
    printf("================================================================\n");
    printf("                     2013 C league Standings\n");
    printf("================================================================\n\n\n");
    printf("      Team               Wins  Losses     pct.    Runs    Runs \n");
    printf("                                                  for    against\n");
    printf("________________________________________________________________\n\n");
      for (i=0; i<12; i++) {
        printf("%-25s %-6.f %-6.f %-10.03f %-8i %-8i\n", stats[i].teams, stats[i].wins, stats[i].losses,
            stats[i].pct, stats[i].runsScored, stats[i].runsAgainst);
    }
    fclose(f);
    printf("\n\n\n");
    pause;
    cls;


    if (finalize == -1) 
        exit(0);
}

Originally Posted by stahta01

First, what is the value of this sizeof(stats[i]) ?
Is it what you think it should be?
If not, the struct packing might be why the size is off.

FYI: Writing struct out as a whole is NOT portable to even the same Compiler version.
It is better to write each element separately unless you do not care if your data is destroyed for each program update.

Tim S.

I expected that stats[i] would be stats[i].teams, stats[i].wins, stats[i].losses, stats[i].pct, stats[i].runsScoredr and stats[i].runsAgainst.

Thanks,

Michael

I originally had the fwrite to write each individual element one at a time. This program will never need to read individual elements. My instructor said it would be easier to write and read in one shot.

Thanks Jim,

I cannot tell though if the displayMenu() writes correctly because the showStats() function is just outputting what is stored in memory in the array of structs.

I know I am overwriting the file everytime with wb, that is the intent.

to: Stahta01, I was not too lazy to write the printf sizeof command. I had not thought about it or really new it was available to use. I did put it in the code and it returned 48. Which is 3 bytes more than expected, so it seems that if padding is included with each element.

I have heard of certain ways to prevent packing but have heard that they are not very portable as well.

Mike

Writing a "binary" file is never really totally portable because of several issues. One of these issues has to do with Endianness. If you are worried about packing then the best solution is to write each individual item to the file, and then when you read the file you read each individual item which you can then put into your structure for the rest of the program to use. But since you are deleting your file every time you open it, you shouldn't worry about any of these issues.

Jim

You can try #pragma pack - or whatever your compiler likes.

Start by reading the section on serialisation in "The Practice of Programming". They provide reasonably portable implementations of the functions pack and unpack, which work in a similar manner as printf and scanf. All your implementation needs to handle is strings (look up strncpy), floats (these are a bit tricky and you can usually get away with assuming the host implementation uses iee-754 natively, but if you want your code to be extra portable, you could probably find a portable iee-754 packer/unpacker somewhere), and 16-bit integers.

As it turns out, everything was written fine for how I needed the program to operate.

The problem lied with the fwrite that wrote to the file as soon as the program started. When I commented that out, I was able to exit the program and re-enter and view the stats on the file and they appeared how they should.

Thanks to all for the help.

Thanks Barney, my instructor could care less about portability but I do. I know that if I ever plan on pursuing anything beyond writing basic programs for class than I will need to have a better hold on portability.