bitmap: add bitmap_unset() function

peff · gitster · commit cc4aa28506e0 · 2020-02-14T10:46:22.000-08:00
We've never needed to unset an individual bit in a bitmap until now.
Typically they start with all bits unset and we bitmap_set() them, or we
are applying another bitmap as a mask. But the easiest way to apply an
object filter to a bitmap result will be to unset the individual bits.

Signed-off-by: Jeff King &lt;peff@peff.net&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/ewah/bitmap.c b/ewah/bitmap.c
@@ -45,6 +45,14 @@ void bitmap_set(struct bitmap *self, size_t pos)
 	self->words[block] |= EWAH_MASK(pos);
 }
 
+void bitmap_unset(struct bitmap *self, size_t pos)
+{
+	size_t block = EWAH_BLOCK(pos);
+
+	if (block < self->word_alloc)
+		self->words[block] &= ~EWAH_MASK(pos);
+}
+
 int bitmap_get(struct bitmap *self, size_t pos)
 {
 	size_t block = EWAH_BLOCK(pos);
diff --git a/ewah/ewok.h b/ewah/ewok.h
@@ -173,6 +173,7 @@ struct bitmap {
 
 struct bitmap *bitmap_new(void);
 void bitmap_set(struct bitmap *self, size_t pos);
+void bitmap_unset(struct bitmap *self, size_t pos);
 int bitmap_get(struct bitmap *self, size_t pos);
 void bitmap_reset(struct bitmap *self);
 void bitmap_free(struct bitmap *self);

Original file line number	Diff line number	Diff line change
`@@ -45,6 +45,14 @@ void bitmap_set(struct bitmap *self, size_t pos)`
`45`	`45`	`self->words[block] \|= EWAH_MASK(pos);`
`46`	`46`	`}`
`47`	`47`
	`48`	`+void bitmap_unset(struct bitmap *self, size_t pos)`
	`49`	`+{`
	`50`	`+ size_t block = EWAH_BLOCK(pos);`
	`51`	`+`
	`52`	`+ if (block < self->word_alloc)`
	`53`	`+ self->words[block] &= ~EWAH_MASK(pos);`
	`54`	`+}`
	`55`	`+`
`48`	`56`	`int bitmap_get(struct bitmap *self, size_t pos)`
`49`	`57`	`{`
`50`	`58`	`size_t block = EWAH_BLOCK(pos);`