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Move Deque from btf into internal and export methods. No other code changes.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,89 @@ | ||
| package internal | ||
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| import "math/bits" | ||
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| // Deque implements a double ended queue. | ||
| type Deque[T any] struct { | ||
| elems []T | ||
| read, write uint64 | ||
| mask uint64 | ||
| } | ||
|
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| func (dq *Deque[T]) Empty() bool { | ||
| return dq.read == dq.write | ||
| } | ||
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| func (dq *Deque[T]) remainingCap() int { | ||
| return len(dq.elems) - int(dq.write-dq.read) | ||
| } | ||
|
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| // Push adds an element to the end. | ||
| func (dq *Deque[T]) Push(e T) { | ||
| if dq.remainingCap() >= 1 { | ||
| dq.elems[dq.write&dq.mask] = e | ||
| dq.write++ | ||
| return | ||
| } | ||
|
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| elems := dq.linearise(1) | ||
| elems = append(elems, e) | ||
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| dq.elems = elems[:cap(elems)] | ||
| dq.mask = uint64(cap(elems)) - 1 | ||
| dq.read, dq.write = 0, uint64(len(elems)) | ||
| } | ||
|
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| // Shift returns the first element or the zero value. | ||
| func (dq *Deque[T]) Shift() T { | ||
| var zero T | ||
|
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| if dq.Empty() { | ||
| return zero | ||
| } | ||
|
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| index := dq.read & dq.mask | ||
| t := dq.elems[index] | ||
| dq.elems[index] = zero | ||
| dq.read++ | ||
| return t | ||
| } | ||
|
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| // Pop returns the last element or the zero value. | ||
| func (dq *Deque[T]) Pop() T { | ||
| var zero T | ||
|
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| if dq.Empty() { | ||
| return zero | ||
| } | ||
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| dq.write-- | ||
| index := dq.write & dq.mask | ||
| t := dq.elems[index] | ||
| dq.elems[index] = zero | ||
| return t | ||
| } | ||
|
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| // linearise the contents of the deque. | ||
| // | ||
| // The returned slice has space for at least n more elements and has power | ||
| // of two capacity. | ||
| func (dq *Deque[T]) linearise(n int) []T { | ||
| length := dq.write - dq.read | ||
| need := length + uint64(n) | ||
| if need < length { | ||
| panic("overflow") | ||
| } | ||
|
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| // Round up to the new power of two which is at least 8. | ||
| // See https://jameshfisher.com/2018/03/30/round-up-power-2/ | ||
| capacity := 1 << (64 - bits.LeadingZeros64(need-1)) | ||
| if capacity < 8 { | ||
| capacity = 8 | ||
| } | ||
|
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| types := make([]T, length, capacity) | ||
| pivot := dq.read & dq.mask | ||
| copied := copy(types, dq.elems[pivot:]) | ||
| copy(types[copied:], dq.elems[:pivot]) | ||
| return types | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| package internal | ||
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| import "testing" | ||
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| func TestDeque(t *testing.T) { | ||
| t.Run("pop", func(t *testing.T) { | ||
| var dq Deque[int] | ||
| dq.Push(1) | ||
| dq.Push(2) | ||
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| if dq.Pop() != 2 { | ||
| t.Error("Didn't pop 2 first") | ||
| } | ||
|
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| if dq.Pop() != 1 { | ||
| t.Error("Didn't pop 1 second") | ||
| } | ||
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| if dq.Pop() != 0 { | ||
| t.Error("Didn't pop zero") | ||
| } | ||
| }) | ||
|
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| t.Run("shift", func(t *testing.T) { | ||
| var td Deque[int] | ||
| td.Push(1) | ||
| td.Push(2) | ||
|
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| if td.Shift() != 1 { | ||
| t.Error("Didn't shift 1 first") | ||
| } | ||
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| if td.Shift() != 2 { | ||
| t.Error("Didn't shift b second") | ||
| } | ||
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| if td.Shift() != 0 { | ||
| t.Error("Didn't shift zero") | ||
| } | ||
| }) | ||
|
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| t.Run("push", func(t *testing.T) { | ||
| var td Deque[int] | ||
| td.Push(1) | ||
| td.Push(2) | ||
| td.Shift() | ||
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| for i := 1; i <= 12; i++ { | ||
| td.Push(i) | ||
| } | ||
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| if td.Shift() != 2 { | ||
| t.Error("Didn't shift 2 first") | ||
| } | ||
| for i := 1; i <= 12; i++ { | ||
| if v := td.Shift(); v != i { | ||
| t.Fatalf("Shifted %d at pos %d", v, i) | ||
| } | ||
| } | ||
| }) | ||
|
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| t.Run("linearise", func(t *testing.T) { | ||
| var td Deque[int] | ||
| td.Push(1) | ||
| td.Push(2) | ||
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| all := td.linearise(0) | ||
| if len(all) != 2 { | ||
| t.Fatal("Expected 2 elements, got", len(all)) | ||
| } | ||
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| if cap(all)&(cap(all)-1) != 0 { | ||
| t.Fatalf("Capacity %d is not a power of two", cap(all)) | ||
| } | ||
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| if all[0] != 1 || all[1] != 2 { | ||
| t.Fatal("Elements don't match") | ||
| } | ||
| }) | ||
| } |