Can't convert binary text to string in C

Question

I found some codes about converting a binary text from a binary file to text file. But my purpose is to convert a binary text from a binary file to string variable because I have to do some string operations after conversion. Here is the code that I found.

FILE *binaryFile = fopen("binary.dat", "rb");
FILE *output_file = fopen("output.txt", "w");

unsigned char byte = 0;
int bits = 0;

for (;;)
{
    char buffer[1024];
    int len = fread(buffer, 1, sizeof(buffer), binaryFile);

    // if there was a read error or EOF, stop
    if (len <= 0)
        break;

    for (int i = 0; i < len; ++i)
    {
        switch (buffer[i])
        {
        // if a binary 1, turn on bit zero
        case '1':
            byte |= 1;
            break;

        // if a binary 0, do nothing
        case '0':
            break;

        // if anything else, skip
        default:
            continue;
        }

        // increment the counter, if we dont yet have 8 bits
        // shift all the bits left by one
        if (++bits < 8)
            byte <<= 1;
        else
        {
            // write out the complete byte
            fwrite(&byte, 1, 1, outputFile);

            // reset for the next byte
            bits = 0;
            byte = 0;
        }
    }
}

// write out any remaining data if the input was not a multiple of 8 in length.
if (bits) {
    fwrite(&byte, 1, 1, outputFile);
}
fclose(xmlFile);

As you can see fwrite method is writing to file. It is working but I want to store it in a string variable.

I tried to find a direct solution but I can't find it. The best solution to this problem is converting to file then read that file and store it to string variable. But I can't do that.

Answer 1

Declare an output buffer array and index:

Replace:

FILE *output_file = fopen("output.txt", "w");

with:

unsigned char output_buffer[MAX_BUF] = "";
int output_index = 0;

Then replace

fwrite(&byte, 1, 1, outputFile);

with:

output_buffer[output_index++] = byte;

You'll need to declare the MAX_BUF macro with the maximum possible string. If you can't specify a maximum, you'll need to use malloc() and realloc() to grow the string dynamically.