From 52721d3a7eb2695c63e22978c0247027b1790f9e Mon Sep 17 00:00:00 2001
From: Robin Voetter <robin@voetter.nl>
Date: Fri, 1 Oct 2021 15:22:51 +0200
Subject: [PATCH] big ints: [add|sub]Wrap tests

---
 lib/std/math/big.zig          |  2 +
 lib/std/math/big/int_test.zig | 97 +++++++++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)

diff --git a/lib/std/math/big.zig b/lib/std/math/big.zig
index 8c0f7f5e1e..e7f8a7fb34 100644
--- a/lib/std/math/big.zig
+++ b/lib/std/math/big.zig
@@ -5,6 +5,7 @@ pub const Rational = @import("big/rational.zig").Rational;
 pub const int = @import("big/int.zig");
 pub const Limb = usize;
 const limb_info = @typeInfo(Limb).Int;
+pub const SignedLimb = std.meta.Int(.signed, limb_info.bits);
 pub const DoubleLimb = std.meta.Int(.unsigned, 2 * limb_info.bits);
 pub const SignedDoubleLimb = std.meta.Int(.signed, 2 * limb_info.bits);
 pub const Log2Limb = std.math.Log2Int(Limb);
@@ -19,6 +20,7 @@ test {
     _ = int;
     _ = Rational;
     _ = Limb;
+    _ = SignedLimb;
     _ = DoubleLimb;
     _ = SignedDoubleLimb;
     _ = Log2Limb;
diff --git a/lib/std/math/big/int_test.zig b/lib/std/math/big/int_test.zig
index bdf75cc6fe..d47346a84c 100644
--- a/lib/std/math/big/int_test.zig
+++ b/lib/std/math/big/int_test.zig
@@ -4,6 +4,7 @@ const testing = std.testing;
 const Managed = std.math.big.int.Managed;
 const Mutable = std.math.big.int.Mutable;
 const Limb = std.math.big.Limb;
+const SignedLimb = std.math.big.SignedLimb;
 const DoubleLimb = std.math.big.DoubleLimb;
 const SignedDoubleLimb = std.math.big.SignedDoubleLimb;
 const maxInt = std.math.maxInt;
@@ -575,6 +576,102 @@ test "big.int add scalar" {
     try testing.expect((try b.to(u32)) == 55);
 }
 
+test "big.int addWrap single-single, unsigned" {
+    var a = try Managed.initSet(testing.allocator, maxInt(u17));
+    defer a.deinit();
+
+    var b = try Managed.initSet(testing.allocator, 10);
+    defer b.deinit();
+
+    try a.addWrap(a.toConst(), b.toConst(), .unsigned, 17);
+
+    try testing.expect((try a.to(u17)) == 9);
+}
+
+test "big.int subWrap single-single, unsigned" {
+    var a = try Managed.initSet(testing.allocator, 0);
+    defer a.deinit();
+
+    var b = try Managed.initSet(testing.allocator, maxInt(u17));
+    defer b.deinit();
+
+    try a.subWrap(a.toConst(), b.toConst(), .unsigned, 17);
+
+    try testing.expect((try a.to(u17)) == 1);
+}
+
+test "big.int addWrap multi-multi, unsigned, limb aligned" {
+    var a = try Managed.initSet(testing.allocator, maxInt(DoubleLimb));
+    defer a.deinit();
+
+    var b = try Managed.initSet(testing.allocator, maxInt(DoubleLimb));
+    defer b.deinit();
+
+    try a.addWrap(a.toConst(), b.toConst(), .unsigned, @bitSizeOf(DoubleLimb));
+
+    try testing.expect((try a.to(DoubleLimb)) == maxInt(DoubleLimb) - 1);
+}
+
+test "big.int subWrap single-multi, unsigned, limb aligned" {
+    var a = try Managed.initSet(testing.allocator, 10);
+    defer a.deinit();
+
+    var b = try Managed.initSet(testing.allocator, maxInt(DoubleLimb) + 100);
+    defer b.deinit();
+
+    try a.subWrap(a.toConst(), b.toConst(), .unsigned, @bitSizeOf(DoubleLimb));
+
+    try testing.expect((try a.to(DoubleLimb)) == maxInt(DoubleLimb) - 88);
+}
+
+test "big.int addWrap single-single, signed" {
+    var a = try Managed.initSet(testing.allocator, maxInt(i21));
+    defer a.deinit();
+
+    var b = try Managed.initSet(testing.allocator, 1 + 1 + maxInt(u21));
+    defer b.deinit();
+
+    try a.addWrap(a.toConst(), b.toConst(), .signed, @bitSizeOf(i21));
+
+    try testing.expect((try a.to(i21)) == minInt(i21));
+}
+
+test "big.int subWrap single-single, signed" {
+    var a = try Managed.initSet(testing.allocator, minInt(i21));
+    defer a.deinit();
+
+    var b = try Managed.initSet(testing.allocator, 1);
+    defer b.deinit();
+
+    try a.subWrap(a.toConst(), b.toConst(), .signed, @bitSizeOf(i21));
+
+    try testing.expect((try a.to(i21)) == maxInt(i21));
+}
+
+test "big.int addWrap multi-multi, signed, limb aligned" {
+    var a = try Managed.initSet(testing.allocator, maxInt(SignedDoubleLimb));
+    defer a.deinit();
+
+    var b = try Managed.initSet(testing.allocator, maxInt(SignedDoubleLimb));
+    defer b.deinit();
+
+    try a.addWrap(a.toConst(), b.toConst(), .signed, @bitSizeOf(SignedDoubleLimb));
+
+    try testing.expect((try a.to(SignedDoubleLimb)) == -2);
+}
+
+test "big.int subWrap single-multi, signed, limb aligned" {
+    var a = try Managed.initSet(testing.allocator, minInt(SignedDoubleLimb));
+    defer a.deinit();
+
+    var b = try Managed.initSet(testing.allocator, 1);
+    defer b.deinit();
+
+    try a.subWrap(a.toConst(), b.toConst(), .signed, @bitSizeOf(SignedDoubleLimb));
+
+    try testing.expect((try a.to(SignedDoubleLimb)) == maxInt(SignedDoubleLimb));
+}
+
 test "big.int sub single-single" {
     var a = try Managed.initSet(testing.allocator, 50);
     defer a.deinit();