shithub: mc

ref: d798a21d16cbd1d866752fbde81871012a789ea8
dir: /lib/std/hashfuncs.myr/

use "alloc"
use "chartype"
use "die"
use "sleq"
use "slpush"
use "types"
use "utf"

pkg std =
	const strhash	: (s : byte[:]	-> uint32)
	const streq	: (a : byte[:], b : byte[:]	-> bool)

	const strcasehash	: (s : byte[:]	-> uint32)
	const strcaseeq	: (a : byte[:], b : byte[:]	-> bool)

	generic ptrhash	: (p : @a#	-> uint32)
	generic ptreq	: (a : @a#, b : @a#	-> bool)

	generic inthash	: (v : @a::(integral,numeric)	-> uint32)
	generic inteq	: (a : @a::(integral,numeric), b : @a::(integral,numeric) -> bool)

	const murmurhash2	: (data : byte[:], seed : uint32 -> uint32)

	generic slhash	: (sl : @a[:] -> uint32)
;;

const Seed = 1234

generic slhash = {data : @a[:]
	-> strhash(slbytes(data))
}

generic slbytes = {data : @a[:]
	var n

	n = data.len * sizeof(@a)
	-> (data : byte#)[:n]
}

const strhash = {s
	-> murmurhash2(s, Seed)
}

const strcaseeq = {a, b
	var ca, cb

	while true
		if a.len == 0 || b.len == 0
			break
		;;
		(ca, a) = std.strstep(a)
		(cb, b) = std.strstep(b)
		if std.tolower(ca) != std.tolower(cb)
			-> false
		;;
	;;
	-> a.len == b.len
}

const strcasehash = {s
	var chars
	var c, h

	chars = [][:]
	while s.len != 0
		(c, s) = std.strstep(s)
		std.slpush(&chars, std.tolower(c))
	;;
	h = murmurhash2(slbytes(chars), Seed)
	slfree(chars)
	-> h
}

const streq = {a, b
	-> sleq(a, b)
}

generic ptrhash = {p : @a#
	var x

	x = (&p : byte#)
	-> murmurhash2(x[0:sizeof(@a#)], Seed)
}

generic ptreq = {a, b
	-> a == b
}

generic inthash = {v : @a::(integral,numeric)
	var p

	p = (&v : byte#)
	-> murmurhash2(p[0:sizeof(@a)], Seed)
}

generic inteq = {a, b
	-> a == b
}

const murmurhash2 = {data, seed
	const m = 0x5bd1e995;
	const r = 24
	var h, k
	
	h = seed ^ data.len
	while data.len >= 4
		k = (data[0] : uint32)
		k |= (data[1] : uint32) << 8
		k |= (data[2] : uint32) << 16
		k |= (data[3] : uint32) << 24

		k *= m
		k ^= k >> r
		k *= m

		h *= m
		h ^= k
		data = data[4:]
	;;

	match data.len
	| 3:
		h ^= (data[2] : uint32) << 16
		h ^= (data[1] : uint32) << 8
		h ^= (data[0] : uint32)
		h *= m
	| 2:
		h ^= (data[1] : uint32) << 8
		h ^= (data[0] : uint32)
		h *= m
	| 1:
		h ^= (data[0] : uint32)
		h *= m
	| 0:	/* nothing */
	| _:	die("0 < len < 4 must be true")
	;;

	h ^= h >> 13
	h *= m
	h ^= h >> 15

	-> h
}