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instance method

IO::Buffer#bit_count

bit_count([offset, [length]]) → integer

static VALUE
io_buffer_bit_count(int argc, VALUE *argv, VALUE self)
{
    rb_check_arity(argc, 0, 2);

    size_t offset, length;
    struct rb_io_buffer_view *buffer = io_buffer_extract_offset_length(self, argc, argv, &offset, &length);

    io_buffer_validate_range(buffer, offset, length);

    const void *base;
    size_t size;
    io_buffer_get_bytes_for_reading(buffer, &base, &size);

    if (length == 0) return SIZET2NUM(0);

    RUBY_ASSERT(base != NULL);
    size_t count = memory_bit_count((const unsigned char *)base + offset, length);

    return SIZET2NUM(count);
}

Returns the number of set bits (1s) in the buffer, also known as the Hamming weight or population count. An optional offset and length can be provided to count bits in a subrange of the buffer.

Example

IO::Buffer.for("\xFF\x00\x0F").bit_count
# => 12

IO::Buffer.for("\xFF\x00\x0F").bit_count(1, 2)
# => 4