CODEWITHSUNDEEP
javacfilebinary
jadou
jadou

Reputation: 61

Read from a file written in C with Java

I have a binary file written in C and I want to read it in java. I wrote the file in C like this :

void Log(TCHAR *name,int age){
    write_int(file, 2012);
    write_int(file, 4);
    write_int(file, 16);
    write_int(file, 12);
    write_int(file, 58);
    write_int(file, 50);

    fwrite(&name, sizeof(name), 1, file);
    fwrite(&age, sizeof(age), 1, file);
    fflush(processusFile);
}

In Java I use the BinaryFile class http://www.heatonresearch.com/code/22/BinaryFile.java and I do this :

RandomAccessFile f = new RandomAccessFile("myfile.dat", "r");
BinaryFile binaryFile = new BinaryFile(f);
ArrayList<String> text = new ArrayList<>();
while (true) {
try {
    Calendar calendar = new GregorianCalendar();
    int year = (int) binaryFile.readDWord();
    int month = (int) binaryFile.readDWord();
    int date = (int) binaryFile.readDWord();
    int hourOfDay = (int) binaryFile.readDWord();
    int minute = (int) binaryFile.readDWord();
    int second = (int) binaryFile.readDWord();

    calendar.set(year, month, date, hourOfDay, minute, second); 
    System.out.println(binaryFile.readFixedString(64));    
    catch (Exception e) {
        break;  
    }
}

This is not working for char* but for int it works. How I can write Strings?

Upvotes: 1

Views: 1044

Answers (4)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726779

This is because sizeof(name) is the size of a char pointer on your system, not the length of the string. You need to write out the length separately from the string, too.

size_t len = strlen(name);
write_int(file, len);
fwrite(&name, len, sizeof(char), file);

Upvotes: 1

Matt
Matt

Reputation: 7160

Your fwrite statement doesn't look right:

fwrite(&name, sizeof(name), 1, file);

You actually want something like:

fwrite(name, sizeof(TCHAR), strlen(name) + 1, file);

Upvotes: 1

stefan bachert
stefan bachert

Reputation: 9606

You must take care type "int".

int in java is always 32bit, not so in C. In C it may be 16,32,64 bit

Upvotes: 1

unwind
unwind

Reputation: 399919

This is wrong:

fwrite(&name, sizeof(name), 1, file);

this will only write a number of characters that correspond to the size of the pointer, typically 4.

If the size you want to write out is fixed (looks like the Java code expects 64 characters), you need to pass that size somehow to Log().

There is no way in C to figure out the size of the array that (might have been) was passed as the first argument to Log() from within the function, which is why you must make it explicit.

Upvotes: 1

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