/* -*- Mode: C++ -*-  */
static size_t CmpDifferentBlockBytes(const Block &a, const Block &b) {
  size_t total = 0;
  size_t i = 0; 
  size_t m = min(a.Size(), b.Size());

  for (; i < m; i++) {
    if (a[i] != b[i]) {
      total++;
    }
  }

  total += a.Size() - i;
  total += b.Size() - i;

  return total;
}

static xoff_t CmpDifferentBytes(const FileSpec &a, const FileSpec &b) {
  Block block_a, block_b;
  xoff_t total = 0;
  typename FileSpec::iterator a_i(a), b_i(b);

  for (; !a_i.Done() && !b_i.Done(); a_i.Next(), b_i.Next()) {

    a_i.Get(&block_a);
    b_i.Get(&block_b);

    total += CmpDifferentBlockBytes(block_a, block_b);
  }

  for (; !a_i.Done(); a_i.Next()) {
    total += a_i.BytesOnBlock();
  }
  for (; !b_i.Done(); b_i.Next()) {
    total += b_i.BytesOnBlock();
  }

  return total;
}

static size_t CmpDifferentBlockBytesAtOffset(const Block &a,
					     const FileSpec &b_spec,
					     xoff_t offset) {
  Block b;
  size_t size = a.Size();
  CHECK_LE(offset, b_spec.Size());
  if (b_spec.Size() < offset + size) {
    size = b_spec.Size() - offset;
  }
  b_spec.Get(&b, offset, size);
  return CmpDifferentBlockBytes(a, b);
}