func BenchmarkDecode(b *testing.B) {
for i := 0; i < b.N; i++ {
Decode(swrap.New([]byte{10}), 5)
Decode(swrap.New([]byte{31, 9}), 5)
Decode(swrap.New([]byte{31, 154, 10}), 5)
Decode(swrap.New([]byte{31, 161, 141, 183, 1}), 5)
}
}
// Encode Integer to N bit prefix
// Integer Representation
//
// [Logic]
// if I < 2^N - 1, encode I on N bits
// else
// encode (2^N - 1) on N bits
// I = I - (2^N - 1)
// while I >= 128
// encode (I % 128 + 128) on 8 bits
// I = I / 128
// encode I on 8 bits
func Encode(I uint32, N uint8) swrap.SWrap {
buf := swrap.New(make([]byte, 0))
if N == 0 {
buf.Add(byte(I))
return buf
}
boundary := uint32(1<<N - 1) // 2^N-1
if I < boundary {
// If I < 2^N - 1, encode I on N bits
buf.Add(byte(I))
} else {
// encode 2^N - 1 on N bits
buf.Add(byte(boundary))
// I = I - (2^N - 1)
I = I - boundary
// While I >= 128
for I >= 128 {
// Encode (I % 128 + 128) on 8 bits
buf.Add(byte(I%128 + 128))
// I = I / 128
I = I / 128
}
// encode (I) on 8 bits
buf.Add(byte(I))
}
return buf
}
func TestDecode(t *testing.T) {
testcases := []struct {
expected, actual uint32
}{
{Decode(swrap.New([]byte{10}), 5), 10},
{Decode(swrap.New([]byte{31, 9}), 5), 40},
{Decode(swrap.New([]byte{31, 154, 10}), 5), 1337},
{Decode(swrap.New([]byte{31, 161, 141, 183, 1}), 5), 3000000},
}
for _, testcase := range testcases {
actual := testcase.actual
expected := testcase.expected
assert.Equal(t, actual, expected)
}
}
func TestStringLiteralDecode(t *testing.T) {
// D.2.1. Literal Header Field with Indexing
var indexing Indexing = WITH
var name, value string = "custom-key", "custom-header"
buf := []byte{
0x40, 0x0a,
0x63, 0x75,
0x73, 0x74,
0x6f, 0x6d,
0x2d, 0x6b,
0x65, 0x79,
0x0d, 0x63,
0x75, 0x73,
0x74, 0x6f,
0x6d, 0x2d,
0x68, 0x65,
0x61, 0x64,
0x65, 0x72,
}
sw := swrap.New(buf)
decoded := DecodeHeader(&sw)
frame, ok := decoded.(*StringLiteral)
assert.Equal(t, ok, true)
expected := NewStringLiteral(indexing, name, value)
assert.Equal(t, frame, expected)
}
func TestReadPrefixedInteger(t *testing.T) {
// 0x1F 0001 1111
// 0x95 1001 0101
// 0x0A 0000 1010
// 0x06 0000 0110
var prefix uint8 = 5
buf := swrap.New([]byte{0x1F, 0x95, 0x0A, 0x06})
expected := []byte{0x1F, 0x95, 0xA}
actual := ReadPrefixedInteger(&buf, prefix)
assert.Equal(t, actual.Bytes(), expected)
}
func TestIndexedHeaderDecode(t *testing.T) {
// D.2.4. Indexed Header Field
var index uint32 = 2
buf := []byte{0x82}
sw := swrap.New(buf)
decoded := DecodeHeader(&sw)
frame, ok := decoded.(*IndexedHeader)
assert.Equal(t, ok, true)
assert.Equal(t, frame.Index, index)
}
func TestIndexedLiteralDecode(t *testing.T) {
// D.2.2. Literal Header Field without Indexing
var indexing Indexing = WITHOUT
var index uint32 = 4
var value string = "/sample/path"
buf := []byte{
0x04, 0x0c,
0x2f, 0x73,
0x61, 0x6d,
0x70, 0x6c,
0x65, 0x2f,
0x70, 0x61,
0x74, 0x68,
}
// table size: empty
sw := swrap.New(buf)
decoded := DecodeHeader(&sw)
frame, ok := decoded.(*IndexedLiteral)
assert.Equal(t, ok, true)
expected := NewIndexedLiteral(indexing, index, value)
assert.Equal(t, frame, expected)
}
// read prefixed N bytes from buffer
// if N bit of first byte is 2^N-1 (ex 1111 in N=4)
// read follow byte until it's smaller than 128
func ReadPrefixedInteger(buf *swrap.SWrap, N uint8) swrap.SWrap {
boundary := byte(1<<N - 1) // 2^N-1
first := buf.Shift()
first = first & boundary // mask N bit
prefix := swrap.New([]byte{first})
// if first byte is smaller than boundary
// it's end of the prefixed bytes
if first < boundary {
return prefix
}
// read bytes while bytes smaller than 128
for {
tmp := buf.Shift()
prefix.Add(tmp)
if tmp < 128 {
break
}
}
return prefix
}
