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a better fix for #21; track ncs in a bitset which allows for detectin…
…g replays even if ncs arrive out of order
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Kevin Manley
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Jan 8, 2016
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,72 @@ | ||
| // Package bitset implments a memory efficient bit array of booleans | ||
| // Adapted from https://github.com/lazybeaver/bitset | ||
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| package auth | ||
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| import "fmt" | ||
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| type BitSet struct { | ||
| bits []uint8 | ||
| size uint64 | ||
| } | ||
|
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| const ( | ||
| bitMaskZero = uint8(0) | ||
| bitMaskOnes = uint8((1 << 8) - 1) | ||
| ) | ||
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| var ( | ||
| bitMasks = [...]uint8{0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80} | ||
| ) | ||
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| func (b *BitSet) getPositionAndMask(index uint64) (uint64, uint8) { | ||
| if index < 0 || index >= b.size { | ||
| panic(fmt.Errorf("BitSet index (%d) out of bounds (size: %d)", index, b.size)) | ||
| } | ||
| position := index >> 3 | ||
| mask := bitMasks[index%8] | ||
| return position, mask | ||
| } | ||
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| func (b *BitSet) Init(size uint64) { | ||
| b.bits = make([]uint8, (size+7)/8) | ||
| b.size = size | ||
| } | ||
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| func (b *BitSet) Size() uint64 { | ||
| return b.size | ||
| } | ||
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| func (b *BitSet) Get(index uint64) bool { | ||
| position, mask := b.getPositionAndMask(index) | ||
| return (b.bits[position] & mask) != 0 | ||
| } | ||
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| func (b *BitSet) Set(index uint64) { | ||
| position, mask := b.getPositionAndMask(index) | ||
| b.bits[position] |= mask | ||
| } | ||
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| func (b *BitSet) Clear(index uint64) { | ||
| position, mask := b.getPositionAndMask(index) | ||
| b.bits[position] &^= mask | ||
| } | ||
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| func (b *BitSet) String() string { | ||
| value := make([]byte, b.size) | ||
| var i uint64 | ||
| for i = 0; i < b.size; i++ { | ||
| if b.Get(i) { | ||
| value[i] = '1' | ||
| } else { | ||
| value[i] = '0' | ||
| } | ||
| } | ||
| return string(value) | ||
| } | ||
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| func NewBitSet(size uint64) *BitSet { | ||
| b := &BitSet{} | ||
| b.Init(size) | ||
| return b | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,79 @@ | ||
| package auth | ||
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| import ( | ||
| "testing" | ||
| ) | ||
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| func TestNew(t *testing.T) { | ||
| var size uint64 = 101 | ||
| bs := NewBitSet(size) | ||
| if bs.Size() != size { | ||
| t.Errorf("Unexpected initialization failure") | ||
| } | ||
| var i uint64 | ||
| for i = 0; i < size; i++ { | ||
| if bs.Get(i) { | ||
| t.Errorf("Newly initialized bitset cannot have true values") | ||
| } | ||
| } | ||
| } | ||
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| func TestGet(t *testing.T) { | ||
| bs := NewBitSet(2) | ||
| bs.Set(0) | ||
| bs.Clear(1) | ||
| if bs.Get(0) != true { | ||
| t.Errorf("Actual: false | Expected: true") | ||
| } | ||
| if bs.Get(1) != false { | ||
| t.Errorf("Actual: true | Expected: false") | ||
| } | ||
| } | ||
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| func TestSet(t *testing.T) { | ||
| bs := NewBitSet(10) | ||
| bs.Set(2) | ||
| bs.Set(3) | ||
| bs.Set(5) | ||
| bs.Set(7) | ||
| actual := bs.String() | ||
| expected := "0011010100" | ||
| if actual != expected { | ||
| t.Errorf("Actual: %s | Expected: %s", actual, expected) | ||
| } | ||
| } | ||
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| func TestClear(t *testing.T) { | ||
| bs := NewBitSet(10) | ||
| var i uint64 | ||
| for i = 0; i < 10; i++ { | ||
| bs.Set(i) | ||
| } | ||
| bs.Clear(0) | ||
| bs.Clear(3) | ||
| bs.Clear(6) | ||
| bs.Clear(9) | ||
| actual := bs.String() | ||
| expected := "0110110110" | ||
| if actual != expected { | ||
| t.Errorf("Actual: %s | Expected: %s", actual, expected) | ||
| } | ||
| } | ||
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| func BenchmarkGet(b *testing.B) { | ||
| bn := uint64(b.N) | ||
| bs := NewBitSet(bn) | ||
| var i uint64 | ||
| for i = 0; i < bn; i++ { | ||
| _ = bs.Get(i) | ||
| } | ||
| } | ||
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| func BenchmarkSet(b *testing.B) { | ||
| bn := uint64(b.N) | ||
| bs := NewBitSet(bn) | ||
| var i uint64 | ||
| for i = 0; i < bn; i++ { | ||
| bs.Set(i) | ||
| } | ||
| } |
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