While looking at the documentation to bit_set() to make sure my "not really necessary" was true, I had some thoughts:

Instead of calling the argument for the number of bits "$bits", I'd be tempted to document it as "$nbits"; some might want to misinterpret that argument name as a bit-mask instead of a number of bits, despite the text on the next line. (ie, when I first saw that, my mind set the "need more information flag" until I got to the next line. (This will especially help clarify if you end up implementing the next suggestion.)

With longer words, there have been times when I want to address multiple disjoint bits simultaneously, such as when a hardware designer separates bits that would logically be grouped. For example, suppose you had a register where in the cheap version of a part, you set a 4bit offset and an offset-enable, where the enable is in bit 4, and the 4 bit offset is bits[3:0] = offset[3:0]; but in a more expensive but pin-and-register compatible version, the same register has an additional 2 bits of offset above the sign bit, so it's bits[6:5] = offset[5:4], bits[4] = enable, bits[3:0] = offset[3:0]. (I design tests for hardware for a living; I've seen much more convoluted register words than that.) To that end, I would want

• bit_mask_disjoint(@bitlist) - where @bitlist (or $bitlist_ref if you prefer) tells which bit numbers should be affected
• bit_set_disjoint($data, $bitmask or \@bitlist, $value) - spreads out the value across the bits that are set in $bitmask, or to the bits indicated by the array reference \@bitlist: yes, this second adds complication... but it's useful for users who think of certain controls being in a different order than the designer does.
• Thus, for my example above:

  my $data = 0x00;
  bit_on($data, 4);   # enables the offset
  my $offsetBits = bit_mask_disjoint(6,5,3,2,1,0);
  foreach my $val ( 0..63 ) {
      bit_set_disjoint($data, $offsetBits, $val);      # sets the offset
  + bits without affecting the enable bit
      ...
  }
  ...
  my $ctrl = 0x00;            # ctrl is a three-bit register
  my $permuteBits = [1,0,2];  # but HW designer and I think of the bits 
  +as being in a different order
  foreach my $val ( 0..7 ) {
      bit_set_disjoint($ctrl, $permuteBits, $val);    # 0:000; 1:010; 2:
  +100; 3:110; 4:001; 5:011; 6:101; 7:111;
      ...
  }
  [download]

(I don't particularly like the _disjoint() naming convention... you might want to see if you can come up with a better one.)

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.