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Merge pull request #12131 from hnakamur/fix_big_int_Managed_mul_sqr_capacity_too_large

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Fix std.math.big.int.Managed capacity after mul and sqr
This commit is contained in:
Andrew Kelley 2022-07-19 18:54:30 -04:00 committed by GitHub
commit 046df9b7d0
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2 changed files with 42 additions and 10 deletions
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20
lib/std/math/big/int.zig
View File

@ -2719,7 +2719,7 @@ pub const Managed = struct {
///
/// Returns an error if memory could not be allocated.
pub fn sub(r: *Managed, a: *const Managed, b: *const Managed) !void {
try r.ensureCapacity(math.max(a.limbs.len, b.limbs.len) + 1);
try r.ensureCapacity(math.max(a.len(), b.len()) + 1);
var m = r.toMutable();
m.sub(a.toConst(), b.toConst());
r.setMetadata(m.positive, m.len);
@ -2780,7 +2780,7 @@ pub const Managed = struct {
if (alias_count == 0) {
m.mulNoAlias(a.toConst(), b.toConst(), rma.allocator);
} else {
const limb_count = calcMulLimbsBufferLen(a.limbs.len, b.limbs.len, alias_count);
const limb_count = calcMulLimbsBufferLen(a.len(), b.len(), alias_count);
const limbs_buffer = try rma.allocator.alloc(Limb, limb_count);
defer rma.allocator.free(limbs_buffer);
m.mul(a.toConst(), b.toConst(), limbs_buffer, rma.allocator);
@ -2813,7 +2813,7 @@ pub const Managed = struct {
if (alias_count == 0) {
m.mulWrapNoAlias(a.toConst(), b.toConst(), signedness, bit_count, rma.allocator);
} else {
const limb_count = calcMulWrapLimbsBufferLen(bit_count, a.limbs.len, b.limbs.len, alias_count);
const limb_count = calcMulWrapLimbsBufferLen(bit_count, a.len(), b.len(), alias_count);
const limbs_buffer = try rma.allocator.alloc(Limb, limb_count);
defer rma.allocator.free(limbs_buffer);
m.mulWrap(a.toConst(), b.toConst(), signedness, bit_count, limbs_buffer, rma.allocator);
@ -2843,11 +2843,11 @@ pub const Managed = struct {
///
/// Returns an error if memory could not be allocated.
pub fn divFloor(q: *Managed, r: *Managed, a: *const Managed, b: *const Managed) !void {
try q.ensureCapacity(a.limbs.len);
try r.ensureCapacity(b.limbs.len);
try q.ensureCapacity(a.len());
try r.ensureCapacity(b.len());
var mq = q.toMutable();
var mr = r.toMutable();
const limbs_buffer = try q.allocator.alloc(Limb, calcDivLimbsBufferLen(a.limbs.len, b.limbs.len));
const limbs_buffer = try q.allocator.alloc(Limb, calcDivLimbsBufferLen(a.len(), b.len()));
defer q.allocator.free(limbs_buffer);
mq.divFloor(&mr, a.toConst(), b.toConst(), limbs_buffer);
q.setMetadata(mq.positive, mq.len);
@ -2860,11 +2860,11 @@ pub const Managed = struct {
///
/// Returns an error if memory could not be allocated.
pub fn divTrunc(q: *Managed, r: *Managed, a: *const Managed, b: *const Managed) !void {
try q.ensureCapacity(a.limbs.len);
try r.ensureCapacity(b.limbs.len);
try q.ensureCapacity(a.len());
try r.ensureCapacity(b.len());
var mq = q.toMutable();
var mr = r.toMutable();
const limbs_buffer = try q.allocator.alloc(Limb, calcDivLimbsBufferLen(a.limbs.len, b.limbs.len));
const limbs_buffer = try q.allocator.alloc(Limb, calcDivLimbsBufferLen(a.len(), b.len()));
defer q.allocator.free(limbs_buffer);
mq.divTrunc(&mr, a.toConst(), b.toConst(), limbs_buffer);
q.setMetadata(mq.positive, mq.len);
@ -2960,7 +2960,7 @@ pub const Managed = struct {
/// r = a * a
pub fn sqr(rma: *Managed, a: *const Managed) !void {
const needed_limbs = 2 * a.limbs.len + 1;
const needed_limbs = 2 * a.len() + 1;
if (rma.limbs.ptr == a.limbs.ptr) {
var m = try Managed.initCapacity(rma.allocator, needed_limbs);

32
lib/std/math/big/int_test.zig
View File

@ -2883,3 +2883,35 @@ test "big int byte swap" {
try byteSwapTest(i32, 0x123456f8, @bitCast(i32, @as(u32, 0xf8563412)));
try byteSwapTest(i48, 0x123456789abc, @bitCast(i48, @as(u48, 0xbc9a78563412)));
}
test "big.int mul multi-multi alias r with a and b" {
var a = try Managed.initSet(testing.allocator, 2 * maxInt(Limb));
defer a.deinit();
try a.mul(&a, &a);
var want = try Managed.initSet(testing.allocator, 4 * maxInt(Limb) * maxInt(Limb));
defer want.deinit();
try testing.expect(a.eq(want));
if (@typeInfo(Limb).Int.bits == 64) {
try testing.expectEqual(@as(usize, 5), a.limbs.len);
}
}
test "big.int sqr multi alias r with a" {
var a = try Managed.initSet(testing.allocator, 2 * maxInt(Limb));
defer a.deinit();
try a.sqr(&a);
var want = try Managed.initSet(testing.allocator, 4 * maxInt(Limb) * maxInt(Limb));
defer want.deinit();
try testing.expect(a.eq(want));
if (@typeInfo(Limb).Int.bits == 64) {
try testing.expectEqual(@as(usize, 5), a.limbs.len);
}
}