authorgravatar for ashe@kivikakk.eeAsherah Connor <ashe@kivikakk.ee> 2021-03-24 16:39:46+11:00
committergravatar for git@vexu.euVeikka Tuominen <git@vexu.eu> 2021-06-11 16:18:10+03:00
loge56ba4cee1040eb0ca4d94e7e4dbfe88a12c171a
tree10cb092230b65cf8bbf13c7873b937fea361cd8d
parentb15e2054384ba683499138fcad0a9503f3aa9e0b

bigint: add ensureAdd(Scalar)Capacity, note aliasing requirements

2 files changed, 33 insertions(+), 8 deletions(-)

lib/std/math/big/int.zig+18-6
......@@ -335,10 +335,10 @@ pub const Mutable = struct {
335335 }
336336 } else {
337337 if (a.limbs.len >= b.limbs.len) {
338 lladd(r.limbs[0..], a.limbs[0..a.limbs.len], b.limbs[0..b.limbs.len]);
338 lladd(r.limbs[0..], a.limbs, b.limbs);
339339 r.normalize(a.limbs.len + 1);
340340 } else {
341 lladd(r.limbs[0..], b.limbs[0..b.limbs.len], a.limbs[0..a.limbs.len]);
341 lladd(r.limbs[0..], b.limbs, a.limbs);
342342 r.normalize(b.limbs.len + 1);
343343 }
344344
......@@ -1685,12 +1685,14 @@ pub const Managed = struct {
16851685
16861686 /// r = a + scalar
16871687 ///
1688 /// r and a may be aliases.
1688 /// r and a may be aliases. If r aliases a, then caller must call
1689 /// `r.ensureAddScalarCapacity` prior to calling `add`.
16891690 /// scalar is a primitive integer type.
16901691 ///
16911692 /// Returns an error if memory could not be allocated.
16921693 pub fn addScalar(r: *Managed, a: Const, scalar: anytype) Allocator.Error!void {
1693 try r.ensureCapacity(math.max(a.limbs.len, calcLimbLen(scalar)) + 1);
1694 assert((r.limbs.ptr != a.limbs.ptr) or r.limbs.len >= math.max(a.limbs.len, calcLimbLen(scalar)) + 1);
1695 try r.ensureAddScalarCapacity(a, scalar);
16941696 var m = r.toMutable();
16951697 m.addScalar(a, scalar);
16961698 r.setMetadata(m.positive, m.len);
......@@ -1698,11 +1700,13 @@ pub const Managed = struct {
16981700
16991701 /// r = a + b
17001702 ///
1701 /// r, a and b may be aliases.
1703 /// r, a and b may be aliases. If r aliases a or b, then caller must call
1704 /// `r.ensureAddCapacity` prior to calling `add`.
17021705 ///
17031706 /// Returns an error if memory could not be allocated.
17041707 pub fn add(r: *Managed, a: Const, b: Const) Allocator.Error!void {
1705 try r.ensureCapacity(math.max(a.limbs.len, b.limbs.len) + 1);
1708 assert((r.limbs.ptr != a.limbs.ptr and r.limbs.ptr != b.limbs.ptr) or r.limbs.len >= math.max(a.limbs.len, b.limbs.len) + 1);
1709 try r.ensureAddCapacity(a, b);
17061710 var m = r.toMutable();
17071711 m.add(a, b);
17081712 r.setMetadata(m.positive, m.len);
......@@ -1748,6 +1752,14 @@ pub const Managed = struct {
17481752 rma.setMetadata(m.positive, m.len);
17491753 }
17501754
1755 pub fn ensureAddScalarCapacity(r: *Managed, a: Const, scalar: anytype) !void {
1756 try r.ensureCapacity(math.max(a.limbs.len, calcLimbLen(scalar)) + 1);
1757 }
1758
1759 pub fn ensureAddCapacity(r: *Managed, a: Const, b: Const) !void {
1760 try r.ensureCapacity(math.max(a.limbs.len, b.limbs.len) + 1);
1761 }
1762
17511763 pub fn ensureMulCapacity(rma: *Managed, a: Const, b: Const) !void {
17521764 try rma.ensureCapacity(a.limbs.len + b.limbs.len + 1);
17531765 }
lib/std/math/big/int_test.zig+15-2
......@@ -538,6 +538,17 @@ test "big.int add sign" {
538538 try testing.expect((try a.to(i32)) == -3);
539539}
540540
541test "big.int add scalar" {
542 var a = try Managed.initSet(testing.allocator, 50);
543 defer a.deinit();
544
545 var b = try Managed.init(testing.allocator);
546 defer b.deinit();
547 try b.addScalar(a.toConst(), 5);
548
549 try testing.expect((try b.to(u32)) == 55);
550}
551
541552test "big.int sub single-single" {
542553 var a = try Managed.initSet(testing.allocator, 50);
543554 defer a.deinit();
......@@ -1563,7 +1574,7 @@ test "big.int pow" {
15631574 }
15641575}
15651576
1566test "bigint regression test for 1 limb overflow with alias" {
1577test "big.int regression test for 1 limb overflow with alias" {
15671578 // Note these happen to be two consecutive Fibonacci sequence numbers, the
15681579 // first two whose sum exceeds 2**64.
15691580 var a = try Managed.initSet(testing.allocator, 7540113804746346429);
......@@ -1571,12 +1582,13 @@ test "bigint regression test for 1 limb overflow with alias" {
15711582 var b = try Managed.initSet(testing.allocator, 12200160415121876738);
15721583 defer b.deinit();
15731584
1585 try a.ensureAddCapacity(a.toConst(), b.toConst());
15741586 try a.add(a.toConst(), b.toConst());
15751587
15761588 try testing.expect(a.toConst().orderAgainstScalar(19740274219868223167) == .eq);
15771589}
15781590
1579test "bigint regression test for something else with alias" {
1591test "big.int regression test for realloc with alias" {
15801592 // Note these happen to be two consecutive Fibonacci sequence numbers, the
15811593 // second of which is the first such number to exceed 2**192.
15821594 var a = try Managed.initSet(testing.allocator, 5611500259351924431073312796924978741056961814867751431689);
......@@ -1584,6 +1596,7 @@ test "bigint regression test for something else with alias" {
15841596 var b = try Managed.initSet(testing.allocator, 9079598147510263717870894449029933369491131786514446266146);
15851597 defer b.deinit();
15861598
1599 try a.ensureAddCapacity(a.toConst(), b.toConst());
15871600 try a.add(a.toConst(), b.toConst());
15881601
15891602 try testing.expect(a.toConst().orderAgainstScalar(14691098406862188148944207245954912110548093601382197697835) == .eq);