it never ends.

nip77/negentropy/storage/vector/helpers.go

@@ -0,0 +1,35 @@
+package vector
+
+import (
+	"bytes"
+	"cmp"
+
+	"fiatjaf.com/nostr/nip77/negentropy"
+)
+
+func itemCompare(a, b negentropy.Item) int {
+	if a.Timestamp == b.Timestamp {
+		return bytes.Compare(a.ID[:], b.ID[:])
+	}
+	return cmp.Compare(a.Timestamp, b.Timestamp)
+}
+
+// binary search with custom function
+func searchItemWithBound(items []negentropy.Item, bound negentropy.Bound) int {
+	n := len(items)
+	// Define x[-1] < target and x[n] >= target.
+	// Invariant: x[i-1] < target, x[j] >= target.
+	i, j := 0, n
+	for i < j {
+		h := int(uint(i+j) >> 1) // avoid overflow when computing h
+		// i ≤ h < j
+		if items[h].Timestamp < bound.Timestamp ||
+			(items[h].Timestamp == bound.Timestamp && bytes.Compare(items[h].ID[:], bound.IDPrefix) == -1) {
+			i = h + 1 // preserves x[i-1] < target
+		} else {
+			j = h // preserves x[j] >= target
+		}
+	}
+	// i == j, x[i-1] < target, and x[j] (= x[i]) >= target  =>  answer is i.
+	return i
+}

nip77/negentropy/storage/vector/vector.go

@@ -1,7 +1,6 @@
 package vector
 
 import (
-	"fmt"
 	"iter"
 	"slices"
 
@@ -24,10 +23,6 @@ func New() *Vector {
 }
 
 func (v *Vector) Insert(createdAt nostr.Timestamp, id nostr.ID) {
-	if len(id) != 64 {
-		panic(fmt.Errorf("bad id size for added item: expected %d bytes, got %d", 32, len(id)/2))
-	}
-
 	item := negentropy.Item{Timestamp: createdAt, ID: id}
 	v.items = append(v.items, item)
 }
@@ -39,12 +34,12 @@ func (v *Vector) Seal() {
 		panic("trying to seal an already sealed vector")
 	}
 	v.sealed = true
-	slices.SortFunc(v.items, negentropy.ItemCompare)
+	slices.SortFunc(v.items, itemCompare)
 }
 
 func (v *Vector) GetBound(idx int) negentropy.Bound {
 	if idx < len(v.items) {
-		return negentropy.Bound{Item: v.items[idx]}
+		return negentropy.Bound{Timestamp: v.items[idx].Timestamp, IDPrefix: v.items[idx].ID[:]}
 	}
 	return negentropy.InfiniteBound
 }
@@ -60,7 +55,7 @@ func (v *Vector) Range(begin, end int) iter.Seq2[int, negentropy.Item] {
 }
 
 func (v *Vector) FindLowerBound(begin, end int, bound negentropy.Bound) int {
-	idx, _ := slices.BinarySearchFunc(v.items[begin:end], bound.Item, negentropy.ItemCompare)
+	idx := searchItemWithBound(v.items[begin:end], bound)
 	return begin + idx
 }
 

nip77/negentropy/types.go

@@ -1,8 +1,6 @@
 package negentropy
 
 import (
-	"bytes"
-	"cmp"
 	"fmt"
 
 	"fiatjaf.com/nostr"
@@ -36,13 +34,6 @@ type Item struct {
 	ID        nostr.ID
 }
 
-func ItemCompare(a, b Item) int {
-	if a.Timestamp == b.Timestamp {
-		return bytes.Compare(a.ID[:], b.ID[:])
-	}
-	return cmp.Compare(a.Timestamp, b.Timestamp)
-}
-
 func (i Item) String() string { return fmt.Sprintf("Item<%d:%x>", i.Timestamp, i.ID[:]) }
 
 type Bound struct {