[dpdk-dev] [PATCH] hash: fix breaking strict-aliasing rules

Pawel Wodkowski pawelx.wodkowski at intel.com
Fri Mar 20 13:47:55 CET 2015


On 2015-03-18 17:51, Yerden Zhumabekov wrote:

>
> -	switch (7 - (data_len & 0x07)) {
> +	i = 7 - (data_len & 0x07);
> +	switch (i) {
>   	case 0:
> -		temp |= (uint64_t) *((const uint8_t *)p64 + 6) << 48;
> -		/* Fallthrough */
>   	case 1:
> -		temp |= (uint64_t) *((const uint8_t *)p64 + 5) << 40;
> -		/* Fallthrough */
>   	case 2:
> -		temp |= (uint64_t) *((const uint8_t *)p64 + 4) << 32;
> -		temp |= *((const uint32_t *)p64);
> +		temp = odd_8byte_mask[i] & *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);
> +		temp = odd_8byte_mask[i] & *p64;
>   		init_val = rte_hash_crc_4byte(temp, init_val);
> -		/* Fallthrough */
>   	default:
>   		break;
>   	}
>

Second thought: is this not an issue here reading 8 bytes by 
dereferencing *p64 if there is less bytes in buffer?

-- 
Pawel


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