// Adler-32 checksum (RFC 1950).
//
// Hare ships a hash::hash-shaped streaming type backed by io::stream;
// we ship the pure-buffer subset here, same shape as lib/hash/fnv.
// `sum32(buf)` matches Hare's adler32::sum32 contract for a single
// write-then-sum: a = 1, b = 0, fold each byte, return b<<16 | a.

package adler32;

def MOD: u32 = 65521u32;

export fn sum32(buf: []u8) u32 = {
	let a: u32 = 1u32;
	let b: u32 = 0u32;
	let i: i32 = 0;
	for (i < buf.len) {
		a = (a + (buf[i]: u32)) % MOD;
		b = (b + a) % MOD;
		i += 1;
	};
	return (b << 16u32) | a;
};