We have macros or inlines for a number of common operations in the siphash
functions. However, in a number of places we still open code feeding
another 64-bits of data into the hash function: an xor, followed by 2
rounds of shuffling, followed by another xor.
Implement an inline function for this, which results in somewhat shortened
code.
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
siphash.c | 52 +++++++++++++++++++++-------------------------------
1 file changed, 21 insertions(+), 31 deletions(-)
diff --git a/siphash.c b/siphash.c
index e1fcf18..716ab62 100644
--- a/siphash.c
+++ b/siphash.c
@@ -91,11 +91,21 @@ static inline void sipround(uint64_t *v, int n)
}
}
+/**
+ * siphash_feed() - Fold 64-bits of data into the hash state
+ * @v: siphash state (4 x 64-bit integers)
+ * @in: New value to fold into hash
+ */
+static inline void siphash_feed(uint64_t *v, uint64_t in)
+{
+ v[3] ^= in;
+ sipround(v, 2);
+ v[0] ^= in;
+}
+
#define POSTAMBLE \
do { \
- v[3] ^= b; \
- sipround(v, 2); \
- v[0] ^= b; \
+ siphash_feed(v, b); \
v[2] ^= 0xff; \
sipround(v, 4); \
b = (v[0] ^ v[1]) ^ (v[2] ^ v[3]); \
@@ -123,9 +133,7 @@ __attribute__((optimize("-fno-strict-aliasing")))
uint64_t siphash_8b(const uint8_t *in, const uint64_t *k)
{
PREAMBLE(8);
- v[3] ^= *(uint64_t *)in;
- sipround(v, 2);
- v[0] ^= *(uint64_t *)in;
+ siphash_feed(v, *(uint64_t *)in);
POSTAMBLE;
return b;
@@ -144,14 +152,9 @@ __attribute__((optimize("-fno-strict-aliasing"))) /* See
siphash_8b() */
uint64_t siphash_12b(const uint8_t *in, const uint64_t *k)
{
uint32_t *in32 = (uint32_t *)in;
- uint64_t combined;
-
- combined = (uint64_t)(*(in32 + 1)) << 32 | *in32;
PREAMBLE(12);
- v[3] ^= combined;
- sipround(v, 2);
- v[0] ^= combined;
+ siphash_feed(v, (uint64_t)(*(in32 + 1)) << 32 | *in32);
b |= *(in32 + 2);
POSTAMBLE;
@@ -174,13 +177,8 @@ uint64_t siphash_20b(const uint8_t *in, const uint64_t *k)
PREAMBLE(20);
- for (i = 0; i < 2; i++, in32 += 2) {
- uint64_t combined = (uint64_t)(*(in32 + 1)) << 32 | *in32;
-
- v[3] ^= combined;
- sipround(v, 2);
- v[0] ^= combined;
- }
+ for (i = 0; i < 2; i++, in32 += 2)
+ siphash_feed(v, (uint64_t)(*(in32 + 1)) << 32 | *in32);
b |= *in32;
POSTAMBLE;
@@ -205,11 +203,8 @@ uint64_t siphash_32b(const uint8_t *in, const uint64_t *k)
PREAMBLE(32);
- for (i = 0; i < 4; i++, in64++) {
- v[3] ^= *in64;
- sipround(v, 2);
- v[0] ^= *in64;
- }
+ for (i = 0; i < 4; i++, in64++)
+ siphash_feed(v, *in64);
POSTAMBLE;
@@ -232,13 +227,8 @@ uint64_t siphash_36b(const uint8_t *in, const uint64_t *k)
PREAMBLE(36);
- for (i = 0; i < 4; i++, in32 += 2) {
- uint64_t combined = (uint64_t)(*(in32 + 1)) << 32 | *in32;
-
- v[3] ^= combined;
- sipround(v, 2);
- v[0] ^= combined;
- }
+ for (i = 0; i < 4; i++, in32 += 2)
+ siphash_feed(v, (uint64_t)(*(in32 + 1)) << 32 | *in32);
b |= *in32;
POSTAMBLE;
--
2.41.0