Difference between revisions of "CAAtom"

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m (dump_caatom.py has been renamed to dump_stuff.py)
m (Grammar corrections)
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There is only 2 exported C function for CAAtom, <tt>CAAtomGetString()</tt> and <tt>CAInternAtom()</tt>, which converts between an integer and its corresponding string value. Most internal code in QuartzCore are identified using atoms. For example, a portion of disassembled code may read:
+
There are only two exported C functions for CAAtom, <tt>CAAtomGetString()</tt> and <tt>CAInternAtom()</tt>, which convert a CAAtom between an integer and its corresponding string value. Most internal code in QuartzCore is identified using atoms. For example, a portion of disassembled code may read:
 
  -[CAGradientLayer setLocations:]:
 
  -[CAGradientLayer setLocations:]:
 
  ;
 
  ;
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  +0000c 0008d9d8            bl                CALayer_setter_kCAValueCopiedPointer
 
  +0000c 0008d9d8            bl                CALayer_setter_kCAValueCopiedPointer
 
  +00010 0008d9dc            ldmia            sp!,{r7,pc}                      ; return
 
  +00010 0008d9dc            ldmia            sp!,{r7,pc}                      ; return
here, the magic number 0xAD is in fact an atom, which is unsurprisingly the value "locations":
+
Here, the magic number 0xAD is in fact an atom, which is unsurprisingly the value "locations":
 
<source lang="javascript">
 
<source lang="javascript">
 
cy# CAAtomGetString(0xad)
 
cy# CAAtomGetString(0xad)
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</source>
 
</source>
  
The CAAtom of 0 always return <tt>&lt;nil&gt;</tt>, and that of an undefined atom is <tt>&lt;unknown&gt;</tt>. Custom atom's value are always larger than the built-in ones.
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The CAAtom of 0 always returns <tt>&lt;nil&gt;</tt>, and that of an undefined atom is <tt>&lt;unknown&gt;</tt>. Custom atom values are always larger than the built-in ones.
  
 
== Tools ==
 
== Tools ==

Revision as of 23:09, 8 October 2013

CAAtom refers to a string for identification in QuartzCore. As of 3.1, there are over 300 internal atoms.

Converting atoms to and from strings

Signature NSString* CAAtomGetString(uint32_t atomicValue);
Available in 2.0 –
Signature uint32_t CAInternAtom(NSString* atommicString);
Available in 2.0 –

There are only two exported C functions for CAAtom, CAAtomGetString() and CAInternAtom(), which convert a CAAtom between an integer and its corresponding string value. Most internal code in QuartzCore is identified using atoms. For example, a portion of disassembled code may read:

-[CAGradientLayer setLocations:]:
;
+00000 0008d9cc             stmdb             sp!,{r7,lr}
+00004 0008d9d0             add               r7,sp,#0x0
+00008 0008d9d4             mov               r1,#0xad
+0000c 0008d9d8             bl                CALayer_setter_kCAValueCopiedPointer
+00010 0008d9dc             ldmia             sp!,{r7,pc}                       ; return

Here, the magic number 0xAD is in fact an atom, which is unsurprisingly the value "locations":

cy# CAAtomGetString(0xad)
"locations"

The CAAtom of 0 always returns <nil>, and that of an undefined atom is <unknown>. Custom atom values are always larger than the built-in ones.

Tools

  • dump_stuff.py — this script can dump internal CAAtom's from the QuartzCore binary.