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authorTimo Teräs <timo.teras@iki.fi>2020-02-17 12:30:12 +0200
committerTimo Teräs <timo.teras@iki.fi>2020-02-17 21:36:28 +0200
commit3694dc5fa2660e2b241d706ec1672beb0a9c24b8 (patch)
tree53bb66d8bb00c64ac90467d933e6899cdf846068 /src
parent6d11ec36e6b6e17978797ef8062d22175717f894 (diff)
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fix murmur3 hash unaligned memory access
- do not do unaligned accesses on non-x86 hardware - clean up the code a little bit
Diffstat (limited to 'src')
-rw-r--r--src/blob.c68
1 files changed, 39 insertions, 29 deletions
diff --git a/src/blob.c b/src/blob.c
index 68a596e..38e370c 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -199,49 +199,59 @@ apk_blob_t apk_blob_pushed(apk_blob_t buffer, apk_blob_t left)
return APK_BLOB_PTR_LEN(buffer.ptr, left.ptr - buffer.ptr);
}
-static uint32_t murmur3_32(const char *key, uint32_t len, uint32_t seed)
+static inline uint32_t rotl32(uint32_t x, int8_t r)
+{
+ return (x << r) | (x >> (32 - r));
+}
+
+static inline uint32_t get_unaligned32(const void *ptr)
+{
+#if defined(__x86_64__) || defined(__i386__)
+ return *(const uint32_t *)ptr;
+#else
+ const uint8_t *p = ptr;
+ return p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
+#endif
+}
+
+static uint32_t murmur3_32(const void *pkey, uint32_t len, uint32_t seed)
{
static const uint32_t c1 = 0xcc9e2d51;
static const uint32_t c2 = 0x1b873593;
- static const uint32_t r1 = 15;
- static const uint32_t r2 = 13;
- static const uint32_t m = 5;
- static const uint32_t n = 0xe6546b64;
- uint32_t hash = seed;
+ const uint8_t *key = pkey;
const int nblocks = len / 4;
- const uint32_t *blocks = (const uint32_t *) key;
+ uint32_t k, h = seed;
int i;
- for (i = 0; i < nblocks; i++) {
- uint32_t k = blocks[i];
+
+ for (i = 0; i < nblocks; i++, key += 4) {
+ k = get_unaligned32(key);
k *= c1;
- k = (k << r1) | (k >> (32 - r1));
+ k = rotl32(k, 15);
k *= c2;
- hash ^= k;
- hash = ((hash << r2) | (hash >> (32 - r2))) * m + n;
+ h ^= k;
+ h = rotl32(h, 13) * 5 + 0xe6546b64;
}
- const uint8_t *tail = (const uint8_t *) (key + nblocks * 4);
- uint32_t k1 = 0;
-
+ k = 0;
switch (len & 3) {
case 3:
- k1 ^= tail[2] << 16;
+ k ^= key[2] << 16;
case 2:
- k1 ^= tail[1] << 8;
+ k ^= key[1] << 8;
case 1:
- k1 ^= tail[0];
- k1 *= c1;
- k1 = (k1 << r1) | (k1 >> (32 - r1));
- k1 *= c2;
- hash ^= k1;
+ k ^= key[0];
+ k *= c1;
+ k = rotl32(k, 15);
+ k *= c2;
+ h ^= k;
}
- hash ^= len;
- hash ^= (hash >> 16);
- hash *= 0x85ebca6b;
- hash ^= (hash >> 13);
- hash *= 0xc2b2ae35;
- hash ^= (hash >> 16);
- return hash;
+ h ^= len;
+ h ^= (h >> 16);
+ h *= 0x85ebca6b;
+ h ^= (h >> 13);
+ h *= 0xc2b2ae35;
+ h ^= (h >> 16);
+ return h;
}
unsigned long apk_blob_hash_seed(apk_blob_t blob, unsigned long seed)