feat: optimize decoding

varint.go

@@ -76,18 +76,18 @@ func ReadUvarint(r io.ByteReader) (uint64, error) {
  // released under the BSD License.
  var x uint64
  var s uint
- for i := 0; ; i++ {
+ for s = 0; ; s += 7 {
  b, err := r.ReadByte()
  if err != nil {
- if err == io.EOF && i != 0 {
+ if err == io.EOF && s != 0 {
  // "eof" will look like a success.
  // If we've read part of a value, this is not a
  // success.
  err = io.ErrUnexpectedEOF
  }
  return 0, err
  }
- if (i == 8 && b >= 0x80) || i >= MaxLenUvarint63 {
+ if (s == 56 && b >= 0x80) || s >= (7*MaxLenUvarint63) {
  // this is the 9th and last byte we're willing to read, but it
  // signals there's more (1 in MSB).
  // or this is the >= 10th byte, and for some reason we're still here.
@@ -100,7 +100,6 @@ func ReadUvarint(r io.ByteReader) (uint64, error) {
  return x | uint64(b)<<s, nil
  }
  x |= uint64(b&0x7f) << s
- s += 7
  }
 }
 

varint_test.go

@@ -156,3 +156,28 @@ func TestUnexpectedEOF(t *testing.T) {
  t.Error("expected n = 0")
  }
 }
+
+func BenchmarkReadUvarint(t *testing.B) {
+ var expected uint64 = 0xffff12
+ reader := bytes.NewReader(ToUvarint(expected))
+ t.ResetTimer()
+ for i := 0; i < t.N; i++ {
+ result, _ := ReadUvarint(reader)
+ if result != expected {
+ t.Fatal("invalid result")
+ }
+ reader.Seek(0, 0)
+ }
+}
+
+func BenchmarkFromUvarint(t *testing.B) {
+ var expected uint64 = 0xffff12
+ uvarint := ToUvarint(expected)
+ t.ResetTimer()
+ for i := 0; i < t.N; i++ {
+ result, _, _ := FromUvarint(uvarint)
+ if result != expected {
+ t.Fatal("invalid result")
+ }
+ }
+}