[Webkit-unassigned] [Bug 54452] Optimize Color::serialized()

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=54452


Darin Adler <darin at apple.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #82442|review?                     |review+
               Flag|                            |




--- Comment #2 from Darin Adler <darin at apple.com>  2011-02-15 09:55:59 PST ---
(From update of attachment 82442)
View in context: https://bugs.webkit.org/attachment.cgi?id=82442&action=review

Looks good.

> Source/WebCore/platform/graphics/Color.cpp:183
> +static inline void appendHexNumber(Vector<UChar>& vector, unsigned char number)

In newer code we’ve been using uint8_t for this more and more. Maybe we should make that a standard thing?

> Source/WebCore/platform/graphics/Color.cpp:185
> +    static const char hexDigits[17] = "0123456789abcdef";

Any particular reason to use lowercase hex here? I normally prefer uppercase when we have a choice. I guess the old code was doing lowercase.

> Source/WebCore/platform/graphics/Color.cpp:191
> +    size_t vectorSize = vector.size();
> +    vector.grow(vectorSize + 2);
> +
> +    vector[vectorSize] = hexDigits[number >> 4];
> +    vector[vectorSize + 1] = hexDigits[number & 0xF];

Is this more efficient than calling append twice?

> Source/WebCore/platform/graphics/Color.cpp:203
> +        result.reserveInitialCapacity(8);

Why 8 and not 7?

> Source/WebCore/platform/graphics/Color.cpp:207
> +        appendHexNumber(result, static_cast<unsigned char>(red()));
> +        appendHexNumber(result, static_cast<unsigned char>(green()));
> +        appendHexNumber(result, static_cast<unsigned char>(blue()));

Are these casts needed? Doesn’t the type conversion happen without a warning even without the cast?

> Source/WebCore/platform/graphics/Color.cpp:208
> +        return String::adopt(result);

Strings use memory more efficiently if they are created with the text in them, because then they use a single block. When we adopt a vector we do extra work that costs both space and also a bit of time.

For this code path, we could just use String::createUninitialized since we know the exact length ahead of time.

We could do the same in the other code path for 0 alpha.

-- 
Configure bugmail: https://bugs.webkit.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.