[dpdk-dev] [PATCH v6 6/7] hash: rte_hash_crc() slices data into 8-byte pieces

[Yerden Zhumabekov]

Calculating hash for data of variable length is more efficient
when that data is sliced into 8-byte pieces. The rest part of data
is hashed using CRC32 functions with either 8 and 4 byte operands.

Signed-off-by: Yerden Zhumabekov <e_zhumabekov at sts.kz>
---
 lib/librte_hash/rte_hash_crc.h |   33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/lib/librte_hash/rte_hash_crc.h b/lib/librte_hash/rte_hash_crc.h
index 435048e..5c04fe4 100644
--- a/lib/librte_hash/rte_hash_crc.h
+++ b/lib/librte_hash/rte_hash_crc.h
@@ -486,7 +486,7 @@ rte_hash_crc_8byte(uint64_t data, uint32_t init_val)
 }

 /**
- * Use crc32 instruction to perform a hash.
+ * Calculate CRC32 hash on user-supplied byte array.
  *
  * @param data
  *   Data to perform hash on.
@@ -501,23 +501,38 @@ static inline uint32_t
 rte_hash_crc(const void *data, uint32_t data_len, uint32_t init_val)
 {
        unsigned i;
-       uint32_t temp = 0;
-       const uint32_t *p32 = (const uint32_t *)data;
+       uint64_t temp = 0;
+       const uint64_t *p64 = (const uint64_t *)data;

-       for (i = 0; i < data_len / 4; i++) {
-               init_val = rte_hash_crc_4byte(*p32++, init_val);
+       for (i = 0; i < data_len / 8; i++) {
+               init_val = rte_hash_crc_8byte(*p64++, init_val);
        }

-       switch (3 - (data_len & 0x03)) {
+       switch (7 - (data_len & 0x07)) {
        case 0:
-               temp |= *((const uint8_t *)p32 + 2) << 16;
+               temp |= (uint64_t) *((const uint8_t *)p64 + 6) << 48;
                /* Fallthrough */
        case 1:
-               temp |= *((const uint8_t *)p32 + 1) << 8;
+               temp |= (uint64_t) *((const uint8_t *)p64 + 5) << 40;
                /* Fallthrough */
        case 2:
-               temp |= *((const uint8_t *)p32);
+               temp |= (uint64_t) *((const uint8_t *)p64 + 4) << 32;
+               temp |= *((const uint32_t *)p64);
+               init_val = rte_hash_crc_8byte(temp, init_val);
+               break;
+       case 3:
+               init_val = rte_hash_crc_4byte(*(const uint32_t *)p64, init_val);
+               break;
+       case 4:
+               temp |= *((const uint8_t *)p64 + 2) << 16;
+               /* Fallthrough */
+       case 5:
+               temp |= *((const uint8_t *)p64 + 1) << 8;
+               /* Fallthrough */
+       case 6:
+               temp |= *((const uint8_t *)p64);
                init_val = rte_hash_crc_4byte(temp, init_val);
+               /* Fallthrough */
        default:
                break;
        }
-- 
1.7.9.5