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Merge pull request #270 from lazyledger/hlib/validate-avaiability
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,108 @@ | ||
| package ipld | ||
|
|
||
| import ( | ||
| crand "crypto/rand" | ||
| "math/big" | ||
|
|
||
| "github.com/ipfs/go-cid" | ||
| "github.com/lazyledger/nmt/namespace" | ||
|
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| "github.com/lazyledger/lazyledger-core/p2p/ipld/plugin/nodes" | ||
| "github.com/lazyledger/lazyledger-core/types" | ||
| ) | ||
|
|
||
| // Sample is a point in 2D space over square. | ||
| type Sample struct { | ||
| Row, Col uint32 | ||
|
|
||
| // src defines the source for sampling, either from column(true) or row(false) root | ||
| src bool | ||
| } | ||
|
|
||
| // SampleSquare randomly picks *num* unique points from arbitrary *width* square | ||
| // and returns them as samples. | ||
| func SampleSquare(squareWidth uint32, num int) []Sample { | ||
| ss := newSquareSampler(squareWidth, num) | ||
| ss.sample(num) | ||
| return ss.samples() | ||
| } | ||
|
|
||
| // Leaf returns leaf info needed for retrieval using data provided with DAHeader. | ||
| func (s Sample) Leaf(dah *types.DataAvailabilityHeader) (cid.Cid, uint32, error) { | ||
| var ( | ||
| leaf uint32 | ||
| root namespace.IntervalDigest | ||
| ) | ||
|
|
||
| // spread leaves retrieval from both Row and Column roots | ||
| if s.src { | ||
| root = dah.ColumnRoots[s.Col] | ||
| leaf = s.Row | ||
| } else { | ||
| root = dah.RowsRoots[s.Row] | ||
| leaf = s.Col | ||
| } | ||
|
|
||
| rootCid, err := nodes.CidFromNamespacedSha256(root.Bytes()) | ||
| if err != nil { | ||
| return cid.Undef, 0, err | ||
| } | ||
|
|
||
| return rootCid, leaf, nil | ||
| } | ||
|
|
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| // Equals check whenever to samples are equal. | ||
| func (s Sample) Equals(to Sample) bool { | ||
| return s.Row == to.Row && s.Col == to.Col | ||
| } | ||
|
|
||
| type squareSampler struct { | ||
| squareWidth uint32 | ||
| smpls map[Sample]struct{} | ||
| } | ||
|
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| func newSquareSampler(squareWidth uint32, expectedSamples int) *squareSampler { | ||
| return &squareSampler{ | ||
| squareWidth: squareWidth, | ||
| smpls: make(map[Sample]struct{}, expectedSamples), | ||
| } | ||
| } | ||
|
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| func (ss *squareSampler) sample(num int) { | ||
| if uint32(num) > ss.squareWidth*ss.squareWidth { | ||
| panic("number of samples must be less than square width") | ||
| } | ||
|
|
||
| done := 0 | ||
| for done < num { | ||
| s := Sample{ | ||
| Row: randUint32(ss.squareWidth), | ||
| Col: randUint32(ss.squareWidth), | ||
| src: randUint32(2) == 0, | ||
| } | ||
|
|
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| if _, ok := ss.smpls[s]; ok { | ||
| continue | ||
| } | ||
|
|
||
| done++ | ||
| ss.smpls[s] = struct{}{} | ||
| } | ||
| } | ||
|
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| func (ss *squareSampler) samples() []Sample { | ||
| samples := make([]Sample, 0, len(ss.smpls)) | ||
| for s := range ss.smpls { | ||
| samples = append(samples, s) | ||
| } | ||
| return samples | ||
| } | ||
|
|
||
| func randUint32(max uint32) uint32 { | ||
| n, err := crand.Int(crand.Reader, big.NewInt(int64(max))) | ||
| if err != nil { | ||
| panic(err) // won't panic as rand.Reader is endless | ||
| } | ||
|
|
||
| return uint32(n.Int64()) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| package ipld | ||
|
|
||
| import ( | ||
| "testing" | ||
|
|
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| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
|
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| func TestSampleSquare(t *testing.T) { | ||
| tests := []struct { | ||
| width uint32 | ||
| samples int | ||
| }{ | ||
| {width: 10, samples: 5}, | ||
| {width: 500, samples: 90}, | ||
| } | ||
|
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||
| for _, tt := range tests { | ||
| ss := SampleSquare(tt.width, tt.samples) | ||
| assert.Len(t, ss, tt.samples) | ||
| // check points are within width | ||
| for _, s := range ss { | ||
| assert.Less(t, s.Row, tt.width) | ||
| assert.Less(t, s.Col, tt.width) | ||
| } | ||
| // checks samples are not equal | ||
| for i, s1 := range ss { | ||
| for j, s2 := range ss { | ||
| if i != j { | ||
| assert.False(t, s1.Equals(s2)) | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
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