BLI_bitmap: ability to declare by-value, and function to find lowest unset bit

In preparation for a larger change (D14162), some BLI_bitmap
functionality that could be submitted separately:

- Ability to declare a fixed size bitmap by-value, without extra
  memory allocation: BLI_BITMAP_DECLARE
- Function to find the index of lowest unset bit:
  BLI_bitmap_find_first_unset
- Test coverage of the above.

Reviewed By: Campbell Barton, Bastien Montagne
Differential Revision: https://developer.blender.org/D15454

1 files changed, 11 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_bitmap.h b/source/blender/blenlib/BLI_bitmap.h
index 19d8525311c..26dc6c7ffc9 100644
--- a/source/blender/blenlib/BLI_bitmap.h
+++ b/source/blender/blenlib/BLI_bitmap.h
@@ -54,6 +54,11 @@ typedef unsigned int BLI_bitmap;
    ((BLI_bitmap *)BLI_memarena_calloc(_mem, BLI_BITMAP_SIZE(_num))))
 
 /**
+ * Declares a bitmap as a variable.
+ */
+#define BLI_BITMAP_DECLARE(_name, _num) BLI_bitmap _name[_BITMAP_NUM_BLOCKS(_num)] = {}
+
+/**
  * Get the value of a single bit at '_index'.
  */
 #define BLI_BITMAP_TEST(_bitmap, _index) \
@@ -137,6 +142,12 @@ void BLI_bitmap_and_all(BLI_bitmap *dst, const BLI_bitmap *src, size_t bits);
  */
 void BLI_bitmap_or_all(BLI_bitmap *dst, const BLI_bitmap *src, size_t bits);
 
+/**
+ * Find index of the lowest unset bit.
+ * Returns -1 if all the bits are set.
+ */
+int BLI_bitmap_find_first_unset(const BLI_bitmap *bitmap, size_t bits);
+
 #ifdef __cplusplus
 }
 #endif