Re: [RFC PATCH 2/3] sha1-array: support appending unsigned char hash

From: Jonathan Tan <jonathantanmy@google.com>
Date: Jul 19, 2017, 23:56 UTC
Message-ID: <20170719165622.78e463fd@twelve2.svl.corp.google.com>
In-Reply-To: <CAGZ79kZ9Ewxv=8fnRZZaQjpyAdv8df81a9aLRkJzEt5ZU0VcTA@mail.gmail.com>

On Tue, 11 Jul 2017 15:06:11 -0700 Stefan Beller <sbeller@google.com> wrote:

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> On Tue, Jul 11, 2017 at 12:48 PM, Jonathan Tan <jonathantanmy@google.com> wrote:
> > In a subsequent patch, sha1_file will need to append object names in the
> > form of "unsigned char *" to oid arrays. Teach sha1-array support for
> > that.
> >
> > Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> 
> This breaks the oid/sha1 barrier?

Not sure what you mean by this. This patch is meant to be a change to make "unsigned char *"-using code able to create/modify oid arrays, while we migrate away from "unsigned char *" - I don't know of any barrier.

Show 7 quoted lines

> I would have expected the caller to do a
> 
>   oid_array_append_oid(&array, sha1_to_oid(sha1));
> 
> with sha1_to_oid working off some static memory, such that the
> call to oid_array_append_oid (which we have as oid_array_append)
> is just as cheap?

The solution you present would need 2 copies (one in sha1_to_oid, and another in oid_array_append), but the solution in this patch only requires one.

> Could you say more in the commit message on why we collude
> sha1 and oids here?

I also don't understand this, but the answer to this is probably the same as the answer to your first question.