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Groups > comp.lang.c > #149247
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Pointer goes to null |
| Date | 2020-01-17 23:25 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <87k15pbr8z.fsf@bsb.me.uk> (permalink) |
| References | (3 earlier) <qv2erl$jp2$1@dont-email.me> <qv2fm6$n8m$1@dont-email.me> <1bab6894-09d3-41e5-8a79-f068db00b0d8@googlegroups.com> <87lfq8ftxs.fsf@bsb.me.uk> <6dcdcd64-5764-4dbc-936e-eb704d374443@googlegroups.com> |
m.nasim85@gmail.com writes:
>> but that does not give blk_cnt == 1 when data_bitlen == 0. Do you
>> really want that?
>>
> Yes, i want that.
> In an implementation for a hash function, there must be something to
> hash. Try running MD5 or SHA against empty string, and you still have
> output.
With SHA-1 the source bits have the length appended (after some padding)
so there is always something to hash. The data length being zero is not
a special case.
> In my case, i process a block of all zeros.
I don't know the structure of the rest of the code, but that would imply
the data_bitlen == 0 is a special case requiring more action than
setting a fake block count. In other words, I'd handle it the top level:
void hash(const void *data, size_t bit_len, void *output_buffer)
{
static char zeros[512/CHAR_BIT];
if (len == 0)
hash(zeros, 512, output_buffer);
else {
...
}
}
Anyway, if setting a block count of 1 when the bit length is 0 works
with the rest of the code there's no point in changing it.
> May be this is not the most ideal method to implement the hashing
> function. however, it still works.
It does seem odd. You've set up two known inputs with the same hash
which is usually considered a bad idea, but it may not matter for your
usage.
--
Ben.
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Pointer goes to null m.nasim85@gmail.com - 2020-01-02 01:34 -0800
Re: Pointer goes to null Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-02 12:47 +0000
Re: Pointer goes to null Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-01-02 08:55 -0500
Re: Pointer goes to null Bart <bc@freeuk.com> - 2020-01-02 18:49 +0000
UB awaits... (Was: Pointer goes to null) gazelle@shell.xmission.com (Kenny McCormack) - 2020-01-02 19:53 +0000
Re: UB awaits... (Was: Pointer goes to null) David Brown <david.brown@hesbynett.no> - 2020-01-02 23:34 +0100
Re: UB awaits... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-03 01:43 +0000
Re: UB awaits... David Brown <david.brown@hesbynett.no> - 2020-01-03 09:50 +0100
Re: UB awaits... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-03 14:30 +0000
Re: UB awaits... David Brown <david.brown@hesbynett.no> - 2020-01-03 17:27 +0100
Re: Pointer goes to null Bart <bc@freeuk.com> - 2020-01-02 14:07 +0000
Re: Pointer goes to null m.nasim85@gmail.com - 2020-01-02 07:29 -0800
Re: Pointer goes to null Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-01-02 10:12 -0800
Re: Pointer goes to null jak <nospam@please.ty> - 2020-01-02 16:46 +0100
Re: Pointer goes to null Barry Schwarz <schwarzb@delq.com> - 2020-01-02 08:50 -0800
Re: Pointer goes to null m.nasim85@gmail.com - 2020-01-03 16:20 -0800
Re: Pointer goes to null Barry Schwarz <schwarzb@delq.com> - 2020-01-03 22:16 -0800
Re: Pointer goes to null m.nasim85@gmail.com - 2020-01-07 03:21 -0800
Re: Pointer goes to null Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-01-07 12:24 -0500
Re: Pointer goes to null Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-01-07 12:38 -0500
Re: Pointer goes to null m.nasim85@gmail.com - 2020-01-15 09:36 -0800
Re: Pointer goes to null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-15 18:36 +0000
Re: Pointer goes to null Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-01-15 17:31 -0500
Re: Pointer goes to null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-16 02:20 +0000
Re: Pointer goes to null m.nasim85@gmail.com - 2020-01-17 14:51 -0800
Re: Pointer goes to null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-17 23:32 +0000
Re: Pointer goes to null m.nasim85@gmail.com - 2020-01-17 14:47 -0800
Re: Pointer goes to null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-17 23:25 +0000
Re: Pointer goes to null James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-15 10:49 -0800
Re: Pointer goes to null m.nasim85@gmail.com - 2020-01-17 14:49 -0800
Re: Pointer goes to null Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-01-07 09:42 -0800
Re: Pointer goes to null m.nasim85@gmail.com - 2020-01-15 09:40 -0800
Re: Pointer goes to null James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-02 22:38 -0500
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