Karsten Blees <karsten.blees@xxxxxxxxx> writes:
> Copying the first bytes of a SHA1 is duplicated in six places, however,
> the implications (wrong byte order on little-endian systems) is documented
> only once.
s/wrong /different /; but other than that I think this is a good
change.
> +`unsigned int sha1hash(const unsigned char *sha1)`::
> +
> + Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code
> + for use in hash tables. Cryptographic hashes are supposed to have
> + uniform distribution, so in contrast to `memhash()`, this just copies
> + the first `sizeof(int)` bytes without shuffling any bits. Note that
> + the results will be different on big-endian and little-endian
> + platforms, so they should not be stored or transferred over the net!
Tone down with s/!/./, perhaps?
Another thing we may want to caution against is to use it as a
tie-breaker that affects the final outcome the user can observe, but
that may be something that goes without saying. I dunno..
> diff --git a/hashmap.h b/hashmap.h
> index a816ad4..ed5425a 100644
> --- a/hashmap.h
> +++ b/hashmap.h
> @@ -13,6 +13,17 @@ extern unsigned int strihash(const char *buf);
> extern unsigned int memhash(const void *buf, size_t len);
> extern unsigned int memihash(const void *buf, size_t len);
>
> +static inline unsigned int sha1hash(const unsigned char *sha1)
> +{
> + /*
> + * Equivalent to 'return *(int *)sha1;', but safe on platforms that
> + * don't support unaligned reads.
> + */
s/int/unsigned &/; other than that, the explanation is good.
> + unsigned int hash;
> + memcpy(&hash, sha1, sizeof(hash));
> + return hash;
> +}
> +
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