ValidateAvailability implementation #270
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,94 @@ | ||
| package ipld | ||
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| import ( | ||
| "math/rand" | ||
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| "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" | ||
| ) | ||
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| // Sample is a point in 2D space over square. | ||
| type Sample struct { | ||
| Row, Col uint32 | ||
| } | ||
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| // 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() | ||
| } | ||
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| // 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 | ||
| ) | ||
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| // spread leaves retrieval from both Row and Column roots | ||
| if rand.Intn(2) == 0 { | ||
| root = dah.ColumnRoots[s.Col] | ||
| leaf = s.Row | ||
| } else { | ||
| root = dah.RowsRoots[s.Row] | ||
| leaf = s.Col | ||
| } | ||
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| rootCid, err := nodes.CidFromNamespacedSha256(root.Bytes()) | ||
| if err != nil { | ||
| return cid.Undef, 0, err | ||
| } | ||
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| 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 | ||
| } | ||
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| 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) { | ||
|
There was a problem hiding this comment. Optional: I think the name There was a problem hiding this comment. Can't agree here. Generate sound like producing something imho, also from the name There was a problem hiding this comment.
We are producing something: random numbers which comprise |
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| if uint32(num) > ss.squareWidth*ss.squareWidth { | ||
| panic("number of samples must be less than square width") | ||
| } | ||
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| done := 0 | ||
| for done < num { | ||
| s := Sample{ | ||
| Row: uint32(rand.Int31n(int32(ss.squareWidth))), | ||
| Col: uint32(rand.Int31n(int32(ss.squareWidth))), | ||
|
There was a problem hiding this comment. See the comment above on the used crypto library. I just double-checked: so this is essentially a math/rand object initialized with a crypto/rand seed. Also, the library is thread-safe which we do not really care about here as we generate these sequentially anyways. IMO, we should use crypto/rand instead. There was a problem hiding this comment. Ok, I used There was a problem hiding this comment. Also, I assumed that we don't need to have extraordinary seed generation as we verify the validity for ourselves only, but linter seems to complain There was a problem hiding this comment. No, we want to use crypto/rand here. Not math/rand. |
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| } | ||
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| if _, ok := ss.smpls[s]; ok { | ||
| continue | ||
| } | ||
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| 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 | ||
| } | ||
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| package ipld | ||
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| 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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Please use crypto/rand.