Writing files in bit form to a file in C

Question

I am implementing the huffman algorithm in C. I have got the basic functionality down up to the point where the binary codewords are obtained. so for example, abcd will be 10001

Answer 1

Collect bits until you have enough bits to fill a byte and then write it..

E.g. something like this:

int current_bit = 0;
unsigned char bit_buffer;

FILE *f;

void WriteBit (int bit)
{
  if (bit)
    bit_buffer |= (1<<current_bit);

  current_bit++;
  if (current_bit == 8)
  {
    fwrite (&bit_buffer, 1, 1, f);
    current_bit = 0;
    bit_buffer = 0;
  }
}

Once you're done writing your bits you have to flush the bit-buffer. To do so just write bits until current_bit equals to zero:

void Flush_Bits (void)
{
  while (current_bit) 
    WriteBit (0);
}