ich will mit dem pseudocode aus wikipedia einen sha1-algorithmus programmieren. es geht mir in erster linie nicht um portability, es soll nur auf meinem system laufen (win64, little endian)
das ist mein code:

template <typename InputIterator>
std::string generate_sha1(InputIterator begin, InputIterator end) {
	long long int seq_size = sizeof(InputIterator::value_type) * (end - begin); // initial size  of input sequence in bytes
	unsigned h[] = { 0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476, 0xC3D2E1F0 }; // initial 32-bit values for sha1 algorithm
	unsigned extension_size = 64 - (seq_size + 8) % 64; // size of 1000... extension in bytes
	std::vector<unsigned char> extend_seq(seq_size + extension_size + 8); // extended sequence = origin sequence + extension + message length
	std::copy(begin, end, extend_seq.begin()); // copy the original sequence
	extend_seq[seq_size] = 128; // add 1 bit at the end of the original sequence
	// fill up rest for 0
	for(long long int n = seq_size + 1; n != seq_size + extension_size; ++n)
		extend_seq[n] = 0;

	long long int be_seq_size = _byteswap_uint64(seq_size * 8); // swap endian of bitwise length of the original sequence
	std::memcpy(&extend_seq[seq_size + extension_size], &be_seq_size, 8); // concatenate big endian length at the end

	// for every 512bit block...
	for(unsigned n = 0; n < extend_seq.size(); n += 64) {
		std::vector<unsigned> words(80); // 32-bit blocks of the extended sequence
		std::memcpy(&words[0], &extend_seq[n], 64); // copy 512 bit into new memory
		std::transform(words.begin(), words.end(), words.begin(), _byteswap_ulong); // transform words to big endian

		// now begin sha1-algorithm
		for(unsigned i = 16; i < 80; ++i) {
			words[i] = left_rotate(words[i - 3] ^ words[i - 8] ^ words[i - 14] ^ words[i - 16], 1);
		}

		int a = h[0], b = h[1], c = h[2], d = h[3], e = h[4], f, k;
		for(unsigned n = 0; n < 79; ++n) {
			if(n >= 60) {
				f = b ^ c ^ d;
				k = 0xCA62C1D6;
			}
			else if(n >= 40 && n <= 59) {
				f = (b & c) | (b & d)  | (c & d);
				k = 0x8F1BBCDC;
			}
			else if(n >= 20 && n <=39) {
				f = b ^ c ^ d;
				k = 0x6ED9EBA1;
			}
			else if(n <= 19) {
				f = (b & c) | (!b & d);
				k = 0x5A827999;
			}

			unsigned tmp = left_rotate(a, 5) + f + e + k + words[n];
			e = d;
			d = c;
			c = left_rotate(b, 30);
			b = a;
			a = tmp;
		}

		h[0] += a;
		h[1] += b;
		h[2] += c;
		h[3] += d;
		h[4] += e;
	}

	// convert result into string, swap endian back to little endian
	std::stringstream ss;
	h[0] = _byteswap_ulong(h[0]);
	h[1] = _byteswap_ulong(h[1]);
	h[2] = _byteswap_ulong(h[2]);
	h[3] = _byteswap_ulong(h[3]);
	h[4] = _byteswap_ulong(h[4]);

	ss << std::hex << h[0] << h[1] << h[2] << h[3] << h[4];
	return ss.str();
}

leider kommt für den hash bei leerem string nicht das richtige ergebnis, weiß aber nicht, wo der fehler sein könnte.
im wikipedia steht, dass man die 32-bit-wörter im big endian haben muss und dass das ergebnis in big endian ist, also konvertiere ich dort um. aber trotzdem klappt es nicht. was ist am endian-swap falsch?

sieht nicht richtig aus.
Die gerechte Strafe für das loop-switch-Idiom.

for(unsigned n = 0; n < 79; ++n)

sieht nicht richtig aus.
Die gerechte Strafe für das loop-switch-Idiom.

stimmt, das war falsch. aber es haut immernoch nicht hin.
mein left_rotate sieht so aus:

unsigned int left_rotate(unsigned int val, int n) {
	char t;
	while(n--) {
		if(val & 0x80000000)  t = 1;
		else t = 0;
		val <<= 1;
		val |= t;
	}
	return val;
}

unsigned int loopless_left_rotate( unsigned int val, int n )
{
	return ( val << n ) | ( val >> ( sizeof( unsigned int ) * CHAR_BIT - n ) );
}