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From: Stefan Beller <>
To: Jeff King <>
Cc: Jonathan Tan <>,
	Jacob Keller <>,
	Simon Ruderich <>, git <>
Subject: Re: [PATCH 3/7] diff.c: do not pass diff options as keydata to hashmap
Date: Fri, 6 Apr 2018 13:41:53 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi Jeff,

On Fri, Apr 6, 2018 at 1:04 PM, Jeff King <> wrote:
> On Mon, Apr 02, 2018 at 03:48:50PM -0700, Stefan Beller wrote:
>> The diff options are passed to the compare function as
>> 'hashmap_cmp_fn_data', which are given when the hashmaps
>> are initialized.
>> A later patch will make use of the keydata to signal
>> different settings for comparision.
> I had to scratch my head here for a moment. Don't we use those options
> as part of the comparison?

Yes we do, but not as passed in here.

Stepping back a bit: There are 2 void pointers passed to the cmp function:

typedef int (*hashmap_cmp_fn)(const void *hashmap_cmp_fn_data,
      const void *entry, const void *entry_or_key,
      const void *keydata);

The hashmap_cmp_fn_data is the same pointer as we pass as
the equals_function data in

extern void hashmap_init(struct hashmap *map,
        hashmap_cmp_fn equals_function,
        const void *equals_function_data,
        size_t initial_size);

whereas the keydata is passed in either directly when calling cmp directly
or in hashmap_get_from_hash:

static inline void *hashmap_get_from_hash(const struct hashmap *map,
          unsigned int hash,
         const void *keydata)
        struct hashmap_entry key;
        hashmap_entry_init(&key, hash);
        return hashmap_get(map, &key, keydata);

It turns out we are passing the struct diff_options *o into the cmp
function twice, once via the inits equals_function_data, as well as
keydata directly. Omit the direct pass in.

This is mostly a cleanup as of now, as it turns out I do not need to
reuse the keydata field anyway.

> I took the "which" to mean "the compare function", but I think you mean
> "we pass these diff options already when the hashmap is initialized".

Oh, yes.

> Maybe something like this would be more clear:
>   When we initialize the hashmap, we give it a pointer to the
>   diff_options, which it then passes along to each call of the
>   hashmap_cmp_fn function. There's no need to pass it a second time as
>   the "keydata" parameter, and our comparison functions never look at
>   keydata.

Thanks for clearing this up, will take as-is.

>   This was a mistake left over from an earlier round of 2e2d5ac184
>   (diff.c: color moved lines differently, 2017-06-30), before hashmap
>   learned to pass the data pointer for us.

That sounds about right.

> (I'm just guessing on the second paragraph based on a quick look at
> git-blame and my recollection from the time).
> -Peff


  reply	other threads:[~2018-04-06 20:41 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-02 22:48 [RFC PATCH 0/7] Moved code detection: ignore space on uniform indentation Stefan Beller
2018-04-02 22:48 ` [PATCH 1/7] xdiff/xdiff.h: remove unused flags Stefan Beller
2018-04-02 22:48 ` [PATCH 2/7] xdiff/xdiffi.c: remove unneeded function declarations Stefan Beller
2018-04-02 22:48 ` [PATCH 3/7] diff.c: do not pass diff options as keydata to hashmap Stefan Beller
2018-04-06 20:04   ` Jeff King
2018-04-06 20:41     ` Stefan Beller [this message]
2018-04-02 22:48 ` [PATCH 4/7] diff.c: adjust hash function signature to match hashmap expectation Stefan Beller
2018-04-02 22:48 ` [PATCH 5/7] diff.c: refactor internal representation for coloring moved code Stefan Beller
2018-04-02 23:51   ` Jonathan Tan
2018-04-03 18:59     ` Stefan Beller
2018-04-06 21:28     ` Stefan Beller
2018-04-06 22:27       ` Jonathan Tan
2018-04-03 19:39   ` Ævar Arnfjörð Bjarmason
2018-04-03 19:49     ` Stefan Beller
2018-04-03 20:44       ` Ævar Arnfjörð Bjarmason
2018-04-03 21:05         ` [PATCH] diff: add a blocks mode for moved code detection Stefan Beller
2018-04-02 22:48 ` [PATCH 6/7] diff.c: decouple white space treatment for move detection from generic option Stefan Beller
2018-04-03  0:31   ` Jonathan Tan
2018-04-02 22:48 ` [PATCH 7/7] diff.c: add --color-moved-ignore-space-delta option Stefan Beller
2018-04-03  0:41   ` Jonathan Tan
2018-04-03 19:22     ` Stefan Beller
2018-04-03 20:38       ` Jonathan Tan
2018-04-02 23:47 ` [RFC PATCH 0/7] Moved code detection: ignore space on uniform indentation Jonathan Tan
2018-04-03  0:03   ` Jacob Keller
2018-04-03 19:00     ` Stefan Beller
2018-04-03 19:55       ` Jacob Keller
  -- strict thread matches above, loose matches on Subject: below --
2018-04-24 21:03 [PATCHv2 " Stefan Beller
2018-04-24 21:03 ` [PATCH 3/7] diff.c: do not pass diff options as keydata to hashmap Stefan Beller

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