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@MSGID: 1@dont-email.me> 740e954d
@REPLY:
<40b905c7-54ae-4e9f-bd6c-990f8e0e804an@googlegroups.com> 755f22c9
@REPLYADDR Lew Pitcher
<lew.pitcher@digitalfreehold.ca>
@REPLYTO 2:5075/128 Lew Pitcher
@CHRS: CP866 2
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@TZUTC: -0000
@PID: Pan/0.139 (Sexual Chocolate; GIT bf56508
git://git.gnome.org/pan2)
@TID: FIDOGATE-5.12-ge4e8b94
On Sun, 20 Aug 2023 23:05:31 -0700, wij wrote:
> manpage of hsearch(3) says:
> ...
> The argument action determines what hsearch() does after an unsuccess-
> ful search. This argument must either have the value ENTER, meaning
> insert a copy of item (and return a pointer to the new hash table entry
> as the function result), or the value FIND, meaning that NULL should be
> returned. (If action is FIND, then data is ignored.)
> ...
>
> When I want to insert an item into the hash table, I invokes
hsearch(item,ENTER).
> But I only want to insert the item when it is not in the hash table. How can I
> do (Only invokes hsearch once. The manpage seems not mentioning
the condition I
> am looking for)?
The version of hsearch() (and it`s manpage) that I have available to me says:
"The hsearch() function searches the hash table for an item with the
same key as item (where "the same" is determined using strcmp(3)), and
if successful returns a pointer to it.
...
The field key points to a null-terminated string which is the search
key. The field data points to data that is associated with that key.
The argument action determines what hsearch() does after an unsuccess-
ful search. This argument must either have the value ENTER, meaning
insert a copy of item (and return a pointer to the new hash table entry
as the function result), or the value FIND, meaning that NULL should be
returned. (If action is FIND, then data is ignored.)"
It seems pretty clear: hsearch() will either
a) find the matching entry in the hash table, and return a pointer to the
struct entry that defines the key and data of the matching entry, or
b) not find the matching entry, and return NULL (when ACTION is set to FIND), or
c) not find the matching entry, insert the supplied struct entry into the
hash table, and return a pointer to it (when ACTION is set to ENTER)
I believe that you are looking for the (c) behaviour; set ACTION to ENTER
when you "want to insert an item into the hash table", and to FIND when you
want to retrieve it.
HTH
--
Lew Pitcher
"In Skills We Trust"
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