[PATCH v2 21/23] ewah: `bitmap_equals_ewah()`

[Taylor Blau <me@ttaylorr.com>]

Prepare to reuse existing pseudo-merge bitmaps by implementing a
`bitmap_equals_ewah()` helper.

This helper will be used to see if a raw bitmap (containing the set of
parents for some pseudo-merge) is equal to any existing pseudo-merge's
commits bitmap (which are stored as EWAH-compressed bitmaps on disk).

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 ewah/bitmap.c | 19 +++++++++++++++++++
 ewah/ewok.h   |  1 +
 2 files changed, 20 insertions(+)

diff --git a/ewah/bitmap.c b/ewah/bitmap.c
index dc2ca190f12..55928dada86 100644
--- a/ewah/bitmap.c
+++ b/ewah/bitmap.c
@@ -261,6 +261,25 @@ int bitmap_equals(struct bitmap *self, struct bitmap *other)
 	return 1;
 }
 
+int bitmap_equals_ewah(struct bitmap *self, struct ewah_bitmap *other)
+{
+	struct ewah_iterator it;
+	eword_t word;
+	size_t i = 0;
+
+	ewah_iterator_init(&it, other);
+
+	while (ewah_iterator_next(&word, &it))
+		if (word != (i < self->word_alloc ? self->words[i++] : 0))
+			return 0;
+
+	for (; i < self->word_alloc; i++)
+		if (self->words[i])
+			return 0;
+
+	return 1;
+}
+
 int bitmap_is_subset(struct bitmap *self, struct bitmap *other)
 {
 	size_t common_size, i;
diff --git a/ewah/ewok.h b/ewah/ewok.h
index 7074a6347b7..5e357e24933 100644
--- a/ewah/ewok.h
+++ b/ewah/ewok.h
@@ -179,6 +179,7 @@ void bitmap_unset(struct bitmap *self, size_t pos);
 int bitmap_get(struct bitmap *self, size_t pos);
 void bitmap_free(struct bitmap *self);
 int bitmap_equals(struct bitmap *self, struct bitmap *other);
+int bitmap_equals_ewah(struct bitmap *self, struct ewah_bitmap *other);
 
 /*
  * Both `bitmap_is_subset()` and `ewah_bitmap_is_subset()` return 1 if the set
-- 
2.45.0.23.gc6f94b99219