[Mesa-dev] [PATCH 1/7] util/mesa-sha1: add a context clone function

[Timothy Arceri]

On 13/03/17 09:47, Grazvydas Ignotas wrote:
> On Mon, Mar 13, 2017 at 12:31 AM, Timothy Arceri <tarceri at itsqueeze.com> wrote:
>> On 13/03/17 05:32, Grazvydas Ignotas wrote:
>>>
>>> This is useful when we need to compute many hashes which all have some
>>> common data hashed in. It works by first hashing the common data and
>>> keeping the context, then for each hashing operation clone the common
>>> context and continue hashing from there.
>>
>>
>> Is this actually anymore performant? Can we have some numbers to go with it?
>> Otherwise I'm not sure its worth the added complexity.
>
> Is a single malloc+memcpy pair really such bad complexity?
> I doubt it has much effect on performance. For me carrying around all
> the stuff that needs to be hashed into the keys (or preparing a blob)
> looks more messy, but I can change to that if you insist.

You need to carry it around anyway. See my comment on patch 6.

>
> Gražvydas
>
>>
>>
>>
>>>
>>> Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
>>> ---
>>>  src/util/mesa-sha1.c | 13 +++++++++++++
>>>  src/util/mesa-sha1.h |  3 +++
>>>  2 files changed, 16 insertions(+)
>>>
>>> diff --git a/src/util/mesa-sha1.c b/src/util/mesa-sha1.c
>>> index e8f1bad..2c47465 100644
>>> --- a/src/util/mesa-sha1.c
>>> +++ b/src/util/mesa-sha1.c
>>> @@ -24,6 +24,7 @@
>>>   * DEALINGS IN THE SOFTWARE.
>>>   */
>>>
>>> +#include <string.h>
>>>  #include "sha1/sha1.h"
>>>  #include "mesa-sha1.h"
>>>
>>> @@ -39,6 +40,18 @@ _mesa_sha1_init(void)
>>>     return (struct mesa_sha1 *) ctx;
>>>  }
>>>
>>> +struct mesa_sha1 *
>>> +_mesa_sha1_clone(const struct mesa_sha1 *ctx)
>>> +{
>>> +   SHA1_CTX *ctx_clone = malloc(sizeof(*ctx_clone));
>>> +
>>> +   if (!ctx_clone)
>>> +      return NULL;
>>> +
>>> +   memcpy(ctx_clone, ctx, sizeof(*ctx_clone));
>>> +   return (struct mesa_sha1 *) ctx_clone;
>>> +}
>>> +
>>>  int
>>>  _mesa_sha1_update(struct mesa_sha1 *ctx, const void *data, int size)
>>>  {
>>> diff --git a/src/util/mesa-sha1.h b/src/util/mesa-sha1.h
>>> index 0be5485..07ca71e 100644
>>> --- a/src/util/mesa-sha1.h
>>> +++ b/src/util/mesa-sha1.h
>>> @@ -34,6 +34,9 @@ struct mesa_sha1;
>>>  struct mesa_sha1 *
>>>  _mesa_sha1_init(void);
>>>
>>> +struct mesa_sha1 *
>>> +_mesa_sha1_clone(const struct mesa_sha1 *ctx);
>>> +
>>>  int
>>>  _mesa_sha1_update(struct mesa_sha1 *ctx, const void *data, int size);
>>>
>>>
>>