lkml.org 
[lkml]   [2017]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 1/2] xxHash: create arch dependent 32/64-bit xxhash()
On Fri, Sep 22, 2017 at 02:18:17AM +0300, Timofey Titovets wrote:
> diff --git a/include/linux/xxhash.h b/include/linux/xxhash.h
> index 9e1f42cb57e9..195a0ae10e9b 100644
> --- a/include/linux/xxhash.h
> +++ b/include/linux/xxhash.h
> @@ -76,6 +76,7 @@
> #define XXHASH_H
>
> #include <linux/types.h>
> +#include <linux/bitops.h> /* BITS_PER_LONG */
>
> /*-****************************
> * Simple Hash Functions

Huh? linux/types.h already brings in BITS_PER_LONG. Look:

linux/types.h
uapi/linux/types.h
uapi/asm/types.h
uapi/asm-generic/types.h
uapi/asm-generic/int-ll64.h
asm/bitsperlong.h

> @@ -107,6 +108,29 @@ uint32_t xxh32(const void *input, size_t length, uint32_t seed);
> */
> uint64_t xxh64(const void *input, size_t length, uint64_t seed);
>
> +#if BITS_PER_LONG == 64
> +typedef u64 xxhash_t;
> +#else
> +typedef u32 xxhash_t;
> +#endif

This is a funny way to spell 'unsigned long' ...

> +/**
> + * xxhash() - calculate 32/64-bit hash based on cpu word size
> + *
> + * @input: The data to hash.
> + * @length: The length of the data to hash.
> + * @seed: The seed can be used to alter the result predictably.
> + *
> + * This function always work as xxh32() for 32-bit systems
> + * and as xxh64() for 64-bit systems.
> + * Because result depends on cpu work size,
> + * the main proporse of that function is for in memory hashing.
> + *
> + * Return: 32/64-bit hash of the data.
> + */
> +

> +xxhash_t xxhash(const void *input, size_t length, uint64_t seed)
> +{
> +#if BITS_PER_LONG == 64
> + return xxh64(input, length, seed);
> +#else
> + return xxh32(input, length, seed);
> +#endif
> +}

Let's move that to the header file and make it a static inline. That way
it doesn't need to be an EXPORT_SYMBOL.

Also, I think the kerneldoc could do with a bit of work. Try this:

/**
* xxhash() - calculate wordsize hash of the input with a given seed
* @input: The data to hash.
* @length: The length of the data to hash.
* @seed: The seed can be used to alter the result predictably.
*
* If the hash does not need to be comparable between machines with
* different word sizes, this function will call whichever of xxh32()
* or xxh64() is faster.
*
* Return: wordsize hash of the data.
*/
static inline
unsigned long xxhash(const void *input, size_t length, unsigned long seed)
{
#if BITS_PER_LONG == 64
return xxh64(input, length, seed);
#else
return xxh32(input, length, seed);
#endif
}

\
 
 \ /
  Last update: 2017-09-25 17:00    [W:0.043 / U:0.856 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site