Re: I'm a total push-over..

On Thu, Jan 24, 2008 at 09:15:43AM -0800, Linus Torvalds wrote:

You can do a perfectly fine 8-bytes-at-a-time hash for almost 100% of all

I suppose 8 bytes for 64-bit platforms and 4 bytes for 32-bits.

	unsigned int name_hash(const char *name, int size)
	{
		hash = HASH_INIT;
		do {
			unsigned char c;
			if (size >= sizeof(long)) {
				unsigned long val = get_unaligned_long(name);
				if (!(val & 0x8080808080808080)) {
					/* Make it equivalent in case */
					val &= ~0x2020202020202020;
					hash = hash_long(hash, val);
					name += sizeof(long);
					size -= sizeof(long);
					continue;
				}
			}

			c = *name;
			if (!(c & 0x80)) {
				hash = hash_long(hash, c & ~0x20);
				name++;
				size--;
				continue;
			}

It is better to use 'while' instead of 'if' here, i.e.:

			while (!((c = *name) & 0x80)) {
				hash = hash_long(hash, c & ~0x20);
				name++;
				if (!--size)
					return hash;
			}

			/* This is the unusual and slowish case */
			hash = hash_utf8_char(hash, c, &name, &size);
		} while (size);
		return hassh;
	}

Dmitry