Fix binaryVarPrefixer to work with more bytes than prefix (#212)

prefix/binary.go

@@ -93,15 +93,17 @@ func (p *binaryVarPrefixer) DecodeLength(maxLen int, data []byte) (int, int, err
  return 0, 0, fmt.Errorf("not enough data length: %d to read: %d bytes", len(data), p.Digits)
  }
 
+ prefBytes := data[:p.Digits]
+
  // it take 4 bytes to encode (u)int32
  uint32Size := 4
 
  // prepend with 0x00 if len of data is less than intSize (4 bytes)
- if len(data) < uint32Size {
- data = append(bytes.Repeat([]byte{0x00}, uint32Size-len(data)), data...)
+ if len(prefBytes) < uint32Size {
+ prefBytes = append(bytes.Repeat([]byte{0x00}, uint32Size-len(prefBytes)), prefBytes...)
  }
 
- dataLen, err := bytesToInt(data)
+ dataLen, err := bytesToInt(prefBytes)
  if err != nil {
  return 0, 0, fmt.Errorf("decode length: %w", err)
  }

prefix/binary_test.go

@@ -152,6 +152,19 @@ func Test_binaryVarPrefixer_DecodeLength(t *testing.T) {
  wantRead: 1,
  wantErr: false,
  },
+ {
+ name: "success(L)_withMoreData",
+ fields: fields{
+ Digits: 1,
+ },
+ args: args{
+ maxLen: 32,
+ data: []byte{0x18, 0x0, 0x0, 0x0},
+ },
+ wantDataLen: 24,
+ wantRead: 1,
+ wantErr: false,
+ },
  {
  name: "success(LLL)",
  fields: fields{
@@ -165,6 +178,19 @@ func Test_binaryVarPrefixer_DecodeLength(t *testing.T) {
  wantRead: 3,
  wantErr: false,
  },
+ {
+ name: "success(LLL)_withMoreData",
+ fields: fields{
+ Digits: 3,
+ },
+ args: args{
+ maxLen: 19999999,
+ data: []byte{0xab, 0xcb, 0xff, 0x0, 0x0, 0x0},
+ },
+ wantDataLen: 11258879,
+ wantRead: 3,
+ wantErr: false,
+ },
  {
  name: "not_enough_data",
  fields: fields{