[v2,3/9] ewah/bitmap: introduce bitmap_word_alloc()

Commit Message

Christian Couder Oct. 19, 2019, 10:35 a.m. UTC

From: Jeff King <[e-mail]>

In a following commit we will need to allocate a variable
number of bitmap words, instead of always 32, so let's add
bitmap_word_alloc() for this purpose.

We will also always access at least one word for each bitmap,
so we want to make sure that at least one is always
allocated.

Signed-off-by: Jeff King <[e-mail]>
Signed-off-by: Christian Couder <[e-mail]>
---
 ewah/bitmap.c | 13 +++++++++----
 ewah/ewok.h   |  1 +
 2 files changed, 10 insertions(+), 4 deletions(-)

Comments

Jonathan Tan Oct. 22, 2019, 5:46 p.m. UTC | #1

> From: Jeff King <[e-mail]>
> 
> In a following commit we will need to allocate a variable
> number of bitmap words, instead of always 32, so let's add
> bitmap_word_alloc() for this purpose.
> 
> We will also always access at least one word for each bitmap,
> so we want to make sure that at least one is always
> allocated.

The last paragraph is not true - we still can allocate 0. (We just ensure
that when we grow, we grow to at least 1.) I think we should just
delete the last paragraph - the first paragraph is sufficient.

Other than that, all patches up to but not including the last one look
good, except the ones that just add a new function because I'll have to
review the last patch to see how they are used.

Christian Couder Oct. 26, 2019, 9:29 a.m. UTC | #2

On Tue, Oct 22, 2019 at 7:46 PM Jonathan Tan <[e-mail]> wrote:
>
> > From: Jeff King <[e-mail]>
> >
> > In a following commit we will need to allocate a variable
> > number of bitmap words, instead of always 32, so let's add
> > bitmap_word_alloc() for this purpose.
> >
> > We will also always access at least one word for each bitmap,
> > so we want to make sure that at least one is always
> > allocated.
>
> The last paragraph is not true - we still can allocate 0. (We just ensure
> that when we grow, we grow to at least 1.) I think we should just
> delete the last paragraph - the first paragraph is sufficient.

Ok, I removed the last paragraph in my current version.

> Other than that, all patches up to but not including the last one look
> good, except the ones that just add a new function because I'll have to
> review the last patch to see how they are used.

Thanks for your review,
Christian.

Patch

diff --git a/ewah/bitmap.c b/ewah/bitmap.c
index 52f1178db4..b5fed9621f 100644
--- a/ewah/bitmap.c
+++ b/ewah/bitmap.c
@@ -22,21 +22,26 @@ 
 #define EWAH_MASK(x) ((eword_t)1 << (x % BITS_IN_EWORD))
 #define EWAH_BLOCK(x) (x / BITS_IN_EWORD)
 
-struct bitmap *bitmap_new(void)
+struct bitmap *bitmap_word_alloc(size_t word_alloc)
 {
 	struct bitmap *bitmap = xmalloc(sizeof(struct bitmap));
-	bitmap->words = xcalloc(32, sizeof(eword_t));
-	bitmap->word_alloc = 32;
+	bitmap->words = xcalloc(word_alloc, sizeof(eword_t));
+	bitmap->word_alloc = word_alloc;
 	return bitmap;
 }
 
+struct bitmap *bitmap_new(void)
+{
+	return bitmap_word_alloc(32);
+}
+
 void bitmap_set(struct bitmap *self, size_t pos)
 {
 	size_t block = EWAH_BLOCK(pos);
 
 	if (block >= self->word_alloc) {
 		size_t old_size = self->word_alloc;
-		self->word_alloc = block * 2;
+		self->word_alloc = block ? block * 2 : 1;
 		REALLOC_ARRAY(self->words, self->word_alloc);
 		memset(self->words + old_size, 0x0,
 			(self->word_alloc - old_size) * sizeof(eword_t));
diff --git a/ewah/ewok.h b/ewah/ewok.h
index 84b2a29faa..1b98b57c8b 100644
--- a/ewah/ewok.h
+++ b/ewah/ewok.h
@@ -172,6 +172,7 @@  struct bitmap {
 };
 
 struct bitmap *bitmap_new(void);
+struct bitmap *bitmap_word_alloc(size_t word_alloc);
 void bitmap_set(struct bitmap *self, size_t pos);
 int bitmap_get(struct bitmap *self, size_t pos);
 void bitmap_reset(struct bitmap *self);