http://d.puremagic.com/issues/show_bug.cgi?id=10403
Summary: memchr optimization for std.algorithm.find
Product: D
Version: unspecified
Platform: All
OS/Version: All
Status: NEW
Severity: enhancement
Priority: P2
Component: Phobos
AssignedTo: [email protected]
ReportedBy: [email protected]
--- Comment #0 from Tommi <[email protected]> 2013-06-18 05:52:38 PDT ---
Add an optimization for:
R find(alias pred = "a == b", R, E)(R haystack, E needle);
...to use the c function memchr when pred is the default "a == b" and...
CASE 1:
All of the following are true:
1) R is an array of elements of type char, byte, ubyte or an enum type whose
base type is one of those.
2) E is integral
3) For the element type of R:
alias Elem = ElementType!R;
...the following is true:
(Elem.min <= needle && needle <= Elem.max)
This is important because memchr only cares about bitwise equality. If the
value of needle is beyound the limits of possible values for type Elem, then we
know needle cannot be found within haystack and the function can just return
early without searching.
CASE 2:
All of the following are true:
1) R is an array of elements of type E
2) E.sizeof == 1
3) For type E equality means bitwise equality
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