ewah/ewah_bitmap.c: avoid open-coding ALLOC_GROW()

ttaylorr · gitster · commit 3b1ca60f8f31 · 2020-12-08T14:48:15.000-08:00
'ewah/ewah_bitmap.c:buffer_grow()' is responsible for growing the buffer
used to store the bits of an EWAH bitmap. It is essentially doing the
same task as the 'ALLOC_GROW()' macro, so use that instead.

This simplifies the callers of 'buffer_grow()', who no longer have to
ask for a specific size, but rather specify how much of the buffer they
need. They also no longer need to guard 'buffer_grow()' behind an if
statement, since 'ALLOC_GROW()' (and, by extension, 'buffer_grow()') is
a noop if the buffer is already large enough.

But, the most significant change is that this fixes a bug when calling
buffer_grow() with both 'alloc_size' and 'new_size' set to 1. In this
case, truncating integer math will leave the new size set to 1, causing
the buffer to never grow.

Instead, let alloc_nr() handle this, which asks for '(new_size + 16) * 3
/ 2' instead of 'new_size * 3 / 2'.

Signed-off-by: Taylor Blau &lt;me@ttaylorr.com&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/ewah/ewah_bitmap.c b/ewah/ewah_bitmap.c
@@ -19,6 +19,7 @@
 #include "git-compat-util.h"
 #include "ewok.h"
 #include "ewok_rlw.h"
+#include "cache.h"
 
 static inline size_t min_size(size_t a, size_t b)
 {
@@ -33,20 +34,13 @@ static inline size_t max_size(size_t a, size_t b)
 static inline void buffer_grow(struct ewah_bitmap *self, size_t new_size)
 {
 	size_t rlw_offset = (uint8_t *)self->rlw - (uint8_t *)self->buffer;
-
-	if (self->alloc_size >= new_size)
-		return;
-
-	self->alloc_size = new_size;
-	REALLOC_ARRAY(self->buffer, self->alloc_size);
+	ALLOC_GROW(self->buffer, new_size, self->alloc_size);
 	self->rlw = self->buffer + (rlw_offset / sizeof(eword_t));
 }
 
 static inline void buffer_push(struct ewah_bitmap *self, eword_t value)
 {
-	if (self->buffer_size + 1 >= self->alloc_size)
-		buffer_grow(self, self->buffer_size * 3 / 2);
-
+	buffer_grow(self, self->buffer_size + 1);
 	self->buffer[self->buffer_size++] = value;
 }
 
@@ -137,8 +131,7 @@ void ewah_add_dirty_words(
 
 		rlw_set_literal_words(self->rlw, literals + can_add);
 
-		if (self->buffer_size + can_add >= self->alloc_size)
-			buffer_grow(self, (self->buffer_size + can_add) * 3 / 2);
+		buffer_grow(self, self->buffer_size + can_add);
 
 		if (negate) {
 			size_t i;
