BLI: new C++ hash table data structures

This commit adds some new hashing based data structures to blenlib.
All of them use open addressing with probing currently.
Furthermore, they support small object optimization, but it is not
customizable yet. I'll add support for this when necessary.
The following main data structures are included:

**Set**
A collection of values, where every value must exist at most once.
This is similar to a Python `set`.

**SetVector**
A combination of a Set and a Vector. It supports fast search for
elements and maintains insertion order when there are no deletes.
All elements are stored in a continuous array. So they can be
iterated over using a normal `ArrayRef`.

**Map**
A set of key-value-pairs, where every key must exist at most once.
This is similar to a Python `dict`.

**StringMap**
A special map for the case when the keys are strings. This case is
fairly common and allows for some optimizations. Most importantly,
many unnecessary allocations can be avoided by storing strings in
a single buffer. Furthermore, the interface of this class uses
`StringRef` to avoid unnecessary conversions.

This commit is a continuation of rB369d5e8ad2bb7.

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_math_base.h b/source/blender/blenlib/BLI_math_base.h
index 7b770f2dd3e..4f841f75d3a 100644
--- a/source/blender/blenlib/BLI_math_base.h
+++ b/source/blender/blenlib/BLI_math_base.h
@@ -158,6 +158,8 @@ MINLINE int power_of_2_min_i(int n);
 
 MINLINE unsigned int power_of_2_max_u(unsigned int x);
 MINLINE unsigned int power_of_2_min_u(unsigned int x);
+MINLINE unsigned int log2_floor_u(unsigned int x);
+MINLINE unsigned int log2_ceil_u(unsigned int x);
 
 MINLINE int divide_round_i(int a, int b);
 MINLINE int mod_i(int i, int n);