in reply to Re: Optimizing a Text Canvas: An inner loop and a cloner
in thread Optimizing a Text Canvas: An inner loop and a cloner

Wow - great ideas...I'll work in trying them out ASAP.

BTW, the AS_BG and AS_FG fields hold standard ANSI FG/BG color codes - e.g. ^[Xm, where X is 30-37 for FG and 40-47 for BG. So, yes, the BG and FG fields could be converted to an integer 0-7 or 10-17, then just add 30 to the resulting output. (Or just use 30-37, 40-47 for the values themselves - doesn't save any bytes to use 0-17.)

However, I've never been very good with bitfields - could you be so kind as to offer a code example of how using bitfields would work? (My apologies for the simplistic question.)

  • Comment on Re^2: Optimizing a Text Canvas: An inner loop and a cloner

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Re^3: Optimizing a Text Canvas: An inner loop and a cloner
by dsheroh (Monsignor) on Jul 06, 2007 at 16:00 UTC
    Sure. Assuming that the U/BOLD/BLINK attributes are 0/1 and that you've already converted your colors into integers (0-255) and copied all of your attribute settings into scalars (which you won't really want to do, but it simplifies the example), I would use: 
    $current_attribs = $as_bg + $as_fg << 8 + $as_u << 16 + $as_bold << 17
+ + $as_blink << 18;

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    This turns the full set of attributes into a 19-bit integer, allowing the CPU to compare two sets of attributes in a single operation when you check whether $current_attribs == $last_attribs. (They could be rendered into only 9 bits by taking the colors down into the 0-7 range (3 bits each instead of 8), but it would add a little time to do the conversion without saving any work later on.)
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      (In response to chatterbox questions...)

      To get the data back out from the bitfield, shift back to the right and use a logical bitwise AND to extract the relevant bits: 

      $as_bg    = $attribs       & 255;
$as_fg    = $attribs >> 8  & 255;
$as_u     = $attribs >> 16 & 1;
$as_bold  = $attribs >> 17 & 1;
$as_blink = $attrib  >> 18 & 1;

      [download]

      update: Corrected && to &.

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      Ahhhh...the lightbulb lites...I think I've got the idea. I'll play with it right now and see what I can come up with. (Many thanks for your help and patience.)

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Re^3: Optimizing a Text Canvas: An inner loop and a cloner
by JosiahBryan (Novice) on Jul 06, 2007 at 17:27 UTC

    Right, I think I've got a bit figured out on the bitfields. However, this doesn't work as expected: 

    
use constant AS_BG    => 0;
use constant AS_FG    => 8;
use constant AS_U     => 16;
use constant AS_BLINK => 17;
use constant AS_BOLD  => 18;

my $test = 0;

#$test |= ($v << $k);  # set $k to $v
#$test &= ~($v << $k); # 
print "Test0:[$test]\n";
$test |= 41 << AS_BG;
$test |= 31 << AS_FG;
$test |= 0 << AS_U;
$test |= 0 << AS_BLINK;
$test |= 1 << AS_BOLD;
print "Test1:[$test]\n";
print "Test parts: ".($test >> AS_BG).", ".($test>>AS_FG).",".($test>>
+AS_U).",".($test>>AS_BLINK).",".($test>>AS_BOLD)."\n";

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    Output: 
    Test0:[0]
Test1:[270121]
Test parts: 270121, 1055,4,2,1

    [download]

    Now, I'm sure I'm missing something here - but what? :-)

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