"Jonathan Tan via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes:
> diff --git a/pack-objects.h b/pack-objects.h
> index b9898a4e64b..15be8368d21 100644
> --- a/pack-objects.h
> +++ b/pack-objects.h
> @@ -207,6 +207,34 @@ static inline uint32_t pack_name_hash(const char *name)
> return hash;
> }
>
> +static inline uint32_t pack_name_hash_v2(const char *name)
> +{
> + uint32_t hash = 0, base = 0, c;
> +
> + if (!name)
> + return 0;
> +
> + while ((c = *name++)) {
> + if (isspace(c))
> + continue;
> + if (c == '/') {
> + base = (base >> 6) ^ hash;
> + hash = 0;
> + } else {
> + /*
> + * 'c' is only a single byte. Reverse it and move
> + * it to the top of the hash, moving the rest to
> + * less-significant bits.
> + */
> + c = (c & 0xF0) >> 4 | (c & 0x0F) << 4;
> + c = (c & 0xCC) >> 2 | (c & 0x33) << 2;
> + c = (c & 0xAA) >> 1 | (c & 0x55) << 1;
> + hash = (hash >> 2) + (c << 24);
> + }
> + }
> + return (base >> 6) ^ hash;
> +}
This works because `c` is masked before any arithmetic is performed on
it, but the cast from potentially signed char to uint32_t still makes
me nervous - if char is signed, it behaves as if it was first cast to
int32_t and only then to uint32_t, as you can see from running the code
below:
#include <stdio.h>
int main() {
signed char c = 128;
unsigned int u = c;
printf("hello %u\n", u);
return 0;
}
I would declare `c` as uint8_t or unsigned char.
