chunks: helper for bit range

chunks/chunk_test.go

@@ -94,10 +94,10 @@ func benchmarkIterator(b *testing.B, newChunk func(int) Chunk) {
 	)
 	var exp []pair
 	for i := 0; i < b.N; i++ {
-		// t += int64(rand.Intn(10000) + 1)
-		t += int64(1000)
+		t += int64(rand.Intn(10000) + 1)
+		// t += int64(1000)
 		// v = rand.Float64()
-		// v += float64(100)
+		v += float64(100)
 		exp = append(exp, pair{t: t, v: v})
 	}
 
@@ -161,10 +161,10 @@ func benchmarkAppender(b *testing.B, newChunk func(int) Chunk) {
 	)
 	var exp []pair
 	for i := 0; i < b.N; i++ {
-		// t += int64(rand.Intn(10000) + 1)
-		t += int64(1000)
+		t += int64(rand.Intn(10000) + 1)
+		// t += int64(1000)
 		// v = rand.Float64()
-		// v += float64(100)
+		v += float64(100)
 		exp = append(exp, pair{t: t, v: v})
 	}
 

chunks/xor.go

@@ -120,13 +120,13 @@ func (a *xorAppender) Append(t int64, v float64) error {
 		switch {
 		case dod == 0:
 			a.b.writeBit(zero)
-		case -8191 <= dod && dod <= 8192:
+		case bitRange(dod, 14):
 			a.b.writeBits(0x02, 2) // '10'
 			a.b.writeBits(uint64(dod), 14)
-		case -65535 <= dod && dod <= 65536:
+		case bitRange(dod, 17):
 			a.b.writeBits(0x06, 3) // '110'
 			a.b.writeBits(uint64(dod), 17)
-		case -524287 <= dod && dod <= 524288:
+		case bitRange(dod, 20):
 			a.b.writeBits(0x0e, 4) // '1110'
 			a.b.writeBits(uint64(dod), 20)
 		default:
@@ -152,6 +152,10 @@ func (a *xorAppender) Append(t int64, v float64) error {
 	return nil
 }
 
+func bitRange(x int64, nbits uint8) bool {
+	return -((1<<(nbits-1))-1) <= x && x <= 1<<(nbits-1)
+}
+
 func (a *xorAppender) writeVDelta(v float64) {
 	vDelta := math.Float64bits(v) ^ math.Float64bits(a.v)