hare

commit 7c4fe19e16e96146707c0a71217172a95bc854b2
parent c05c29658669c85794cca2bde5e94865c9a63c28
Author: Armin Preiml <apreiml@strohwolke.at>
Date:   Fri, 17 Jun 2022 14:35:34 +0200

crypto::math: add divu32

Signed-off-by: Armin Preiml <apreiml@strohwolke.at>

Diffstat:
A
crypto/math/arithm.ha
 | 
61
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
M
scripts/gen-stdlib
 | 
2
+-
M
stdlib.mk
 | 
2
++

3 files changed, 64 insertions(+), 1 deletion(-)
diff --git a/crypto/math/arithm.ha b/crypto/math/arithm.ha
@@ -0,0 +1,61 @@
+// License: MPL-2.0
+// (c) 2022 Armin Preiml <apreiml@strohwolke.at>
+//
+// The following code was initially ported from BearSSL.
+//
+// Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// Returns the quotient and remainder of (hi, lo) divided by y:
+// quo = (hi, lo) / y, rem = (hi, lo) % y with the dividend bits' upper
+// half in parameter hi and the lower half in parameter lo.
+// Panics for y == 0 (division by zero) or y <= hi (quotient overflow).
+export fn divu32(hi: u32, lo: u32, y: u32) (u32, u32) = {
+	assert(y != 0);
+	assert(y > hi);
+
+	let q: u32 = 0;
+	const ch: u32 = equ32(hi, y);
+	hi = muxu32(ch, 0, hi);
+	for (let k: u32 = 31; k > 0; k -= 1) {
+		const j = (32 - k);
+		const w = (hi << j) | (lo >> k);
+		const ctl = geu32(w, y) | (hi >> k);
+		const hi2 = (w - y) >> j;
+		const lo2 = lo - (y << k);
+		hi = muxu32(ctl, hi2, hi);
+		lo = muxu32(ctl, lo2, lo);
+		q |= ctl << k;
+	};
+	let cf = geu32(lo, y) | hi;
+	q |= cf;
+	const r = muxu32(cf, lo - y, lo);
+	return (q, r);
+};
+
+@test fn divu32() void = {
+	const r = divu32(1, 4294967295, 9);
+	assert(r.0 == 954437176);
+	assert(r.1 == 7);
+
+	const r = divu32(0, 485, 13);
+	assert(r.0 == 37);
+	assert(r.1 == 4);
+};
diff --git a/scripts/gen-stdlib b/scripts/gen-stdlib
@@ -371,7 +371,7 @@ crypto_mac() {
 
 crypto_math() {
 	gen_srcs crypto::math \
-		bits.ha
+		arithm.ha bits.ha
 	gen_ssa crypto::math
 }
 
diff --git a/stdlib.mk b/stdlib.mk
@@ -892,6 +892,7 @@ $(HARECACHE)/crypto/mac/crypto_mac-any.ssa: $(stdlib_crypto_mac_any_srcs) $(stdl
 
 # crypto::math (+any)
 stdlib_crypto_math_any_srcs = \
+	$(STDLIB)/crypto/math/arithm.ha \
 	$(STDLIB)/crypto/math/bits.ha
 
 $(HARECACHE)/crypto/math/crypto_math-any.ssa: $(stdlib_crypto_math_any_srcs) $(stdlib_rt)
@@ -3040,6 +3041,7 @@ $(TESTCACHE)/crypto/mac/crypto_mac-any.ssa: $(testlib_crypto_mac_any_srcs) $(tes
 
 # crypto::math (+any)
 testlib_crypto_math_any_srcs = \
+	$(STDLIB)/crypto/math/arithm.ha \
 	$(STDLIB)/crypto/math/bits.ha
 
 $(TESTCACHE)/crypto/math/crypto_math-any.ssa: $(testlib_crypto_math_any_srcs) $(testlib_rt)