From e4ee891759b08d3edb258b34f00b4ae8e3298d06 Mon Sep 17 00:00:00 2001
From: Zachary T Welch <zw@superlucidity.net>
Date: Sat, 14 Nov 2009 10:27:34 -0800
Subject: improve buf_cmp and buf_cmp_mask helpers

Rewrite buf_cmp to use memcpy for bulk of comparison.  Add static
helper to perform comparison of trailing byte, which uses another
static helper to perform a maksed comparison.  The masked comparison
helper is used by the buf_cmp_mask to simplify its loop.
Improve types to use void *, unsigned, and return bool.
---
 src/helper/binarybuffer.c | 73 ++++++++++++++++++++++++-----------------------
 src/helper/binarybuffer.h |  6 ++--
 2 files changed, 40 insertions(+), 39 deletions(-)

diff --git a/src/helper/binarybuffer.c b/src/helper/binarybuffer.c
index 0def9485..865d3a37 100644
--- a/src/helper/binarybuffer.c
+++ b/src/helper/binarybuffer.c
@@ -65,52 +65,53 @@ uint8_t* buf_cpy(const uint8_t *from, uint8_t *to, int size)
 	return to;
 }
 
-int buf_cmp(const uint8_t *buf1, const uint8_t *buf2, int size)
+static bool buf_cmp_masked(uint8_t a, uint8_t b, uint8_t m)
 {
-	if (!buf1 || !buf2)
-		return 1;
+	return (a & m) != (b & m);
+}
+static bool buf_cmp_trailing(uint8_t a, uint8_t b, uint8_t m, unsigned trailing)
+{
+	uint8_t mask = (1 << trailing) - 1;
+	return buf_cmp_masked(a, b, mask & m);
+}
 
-	for (unsigned i = 0, num_bytes = CEIL(size, 8); i < num_bytes; i++)
-	{
-		/* last byte */
-		/* mask out bits that don't really belong to the buffer if size isn't a multiple of 8 bits */
-		if ((size % 8) && (i == num_bytes -1))
-		{
-			if ((buf1[i] & ((1 << (size % 8)) - 1)) != (buf2[i] & ((1 << (size % 8)) - 1)))
-				return 1;
-		}
-		else
-		{
-			if (buf1[i] != buf2[i])
-				return 1;
-		}
-	}
+bool buf_cmp(const void *_buf1, const void *_buf2, unsigned size)
+{
+	if (!_buf1 || !_buf2)
+		return _buf1 != _buf2;
 
-	return 0;
+	unsigned last = size / 8;
+	if (memcmp(_buf1, _buf2, last) != 0)
+		return false;
+
+	unsigned trailing = size % 8;
+	if (!trailing)
+		return false;
+
+	const uint8_t *buf1 = _buf1, *buf2 = _buf2;
+	return buf_cmp_trailing(buf1[last], buf2[last], 0xff, trailing);
 }
 
-int buf_cmp_mask(const uint8_t *buf1, const uint8_t *buf2, const uint8_t *mask, int size)
+bool buf_cmp_mask(const void *_buf1, const void *_buf2,
+		const void *_mask, unsigned size)
 {
-	for (unsigned i = 0, num_bytes = CEIL(size, 8); i < num_bytes; i++)
+	if (!_buf1 || !_buf2)
+		return _buf1 != _buf2 || _buf1 != _mask;
+
+	const uint8_t *buf1 = _buf1, *buf2 = _buf2, *mask = _mask;
+	unsigned last = size / 8;
+	for (unsigned i = 0; i < last; i++)
 	{
-		/* last byte */
-		/* mask out bits that don't really belong to the buffer if size isn't a multiple of 8 bits */
-		if ((size % 8) && (i == num_bytes -1))
-		{
-			if ((buf1[i] & ((1 << (size % 8)) - 1) & mask[i]) !=
-				(buf2[i] & ((1 << (size % 8)) - 1) & mask[i]))
-				return 1;
-		}
-		else
-		{
-			if ((buf1[i] & mask[i]) != (buf2[i] & mask[i]))
-				return 1;
-		}
+		if (buf_cmp_masked(buf1[i], buf2[i], mask[i]))
+			return true;
 	}
-
-	return 0;
+	unsigned trailing = size % 8;
+	if (!trailing)
+		return false;
+	return buf_cmp_trailing(buf1[last], buf2[last], mask[last], trailing);
 }
 
+
 uint8_t* buf_set_ones(uint8_t *buf, int count)
 {
 	for (unsigned i = 0, num_bytes = CEIL(count, 8); i < num_bytes; i++)
diff --git a/src/helper/binarybuffer.h b/src/helper/binarybuffer.h
index 49050074..a51c2e57 100644
--- a/src/helper/binarybuffer.h
+++ b/src/helper/binarybuffer.h
@@ -70,9 +70,9 @@ static inline uint32_t buf_get_u32(const uint8_t* buffer,
 /// flip_u32 inverts the bit order inside a 32-bit word (31..0 -> 0..31)
 uint32_t flip_u32(uint32_t value, unsigned int num);
 
-int buf_cmp(const uint8_t *buf1, const uint8_t *buf2, int size);
-int buf_cmp_mask(const uint8_t *buf1, const uint8_t *buf2,
-		const uint8_t *mask, int size);
+bool buf_cmp(const void *buf1, const void *buf2, unsigned size);
+bool buf_cmp_mask(const void *buf1, const void *buf2,
+		const void *mask, unsigned size);
 uint8_t* buf_cpy(const uint8_t *from, uint8_t *to, int size);
 
 uint8_t* buf_set_ones(uint8_t *buf, int count);
-- 
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