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export SSLKEYLOGFILE=~/sslkey.log

# 使用http1.1 请求
curl --http1.1 -v 'https://kiosk.io/admin/' \
  -H 'authority: kiosk.io' \
  -H 'pragma: no-cache' \
  -H 'cache-control: no-cache' \
  -H 'sec-ch-ua: " Not;A Brand";v="99", "Google Chrome";v="97", "Chromium";v="97"' \
  -H 'sec-ch-ua-mobile: ?0' \
  -H 'sec-ch-ua-platform: "Linux"' \
  ....  多加一些 Header 可以体现出压缩效率
  -H 'cookie: 1234567890qwertyuiopasdfghjklzxcvbnm' -o /dev/null \
  
# 使用http2 请求
curl --http2 -v 'https://kiosk.io/admin/' \
  ....  Header 保持和H1一样，这里省略
  --next --http2 -v 'https://kiosk.io/admin/' \
  ....  Header 省略

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type headerFieldTable struct {
	// As in hpack, unique ids  are 1-based. The unique id for ents[k] is k + evictCount + 1.
	ents       []HeaderField
	evictCount uint64

	// byName maps a HeaderField name to the unique id of the newest entry with the same name.
	byName map[string]uint64

	// byNameValue maps a HeaderField name/value pair to the unique id of the newest
	byNameValue map[pairNameValue]uint64
}

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func (t *headerFieldTable) addEntry(f HeaderField) {
	id := uint64(t.len()) + t.evictCount + 1
	t.byName[f.Name] = id
	t.byNameValue[pairNameValue{f.Name, f.Value}] = id
	t.ents = append(t.ents, f)
}

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func (t *headerFieldTable) evictOldest(n int) {
	if n > t.len() {
		panic(fmt.Sprintf("evictOldest(%v) on table with %v entries", n, t.len()))
	}
	for k := 0; k < n; k++ {
		f := t.ents[k]
		id := t.evictCount + uint64(k) + 1
		if t.byName[f.Name] == id {
			delete(t.byName, f.Name)
		}
		if p := (pairNameValue{f.Name, f.Value}); t.byNameValue[p] == id {
			delete(t.byNameValue, p)
		}
	}
	copy(t.ents, t.ents[n:])
	for k := t.len() - n; k < t.len(); k++ {
		t.ents[k] = HeaderField{} // so strings can be garbage collected
	}
	t.ents = t.ents[:t.len()-n]
	if t.evictCount+uint64(n) < t.evictCount {
		panic("evictCount overflow")
	}
	t.evictCount += uint64(n)
}

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func (t *headerFieldTable) search(f HeaderField) (i uint64, nameValueMatch bool) {
	if !f.Sensitive {
		if id := t.byNameValue[pairNameValue{f.Name, f.Value}]; id != 0 {
			return t.idToIndex(id), true
		}
	}
	if id := t.byName[f.Name]; id != 0 {
		return t.idToIndex(id), false
	}
	return 0, false
}

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func (t *headerFieldTable) idToIndex(id uint64) uint64 {
	if id <= t.evictCount {
		panic(fmt.Sprintf("id (%v) <= evictCount (%v)", id, t.evictCount))
	}
	k := id - t.evictCount - 1 // convert id to an index t.ents[k]
	if t != staticTable {
		return uint64(t.len()) - k // dynamic table
	}
	return k + 1
}

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var staticTable = newStaticTable()
func newStaticTable() *headerFieldTable {
	t := &headerFieldTable{}
	t.init()
	for _, e := range staticTableEntries[:] {
		t.addEntry(e)
	}
	return t
}
var staticTableEntries = [...]HeaderField{
	{Name: ":authority"},
	{Name: ":method", Value: "GET"},
	{Name: ":method", Value: "POST"},
  // 此处省略代码
	{Name: "www-authenticate"},
}

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// WriteField encodes f into a single Write to e's underlying Writer.
// This function may also produce bytes for "Header Table Size Update"
// if necessary. If produced, it is done before encoding f.
func (e *Encoder) WriteField(f HeaderField) error {
	e.buf = e.buf[:0]

// 收到 SETTINGS 帧，且包含 SettingHeaderTableSize 表示动态表需要更新，才会进入到这里	
	if e.tableSizeUpdate {	     
        e.tableSizeUpdate = false
		if e.minSize < e.dynTab.maxSize {
			e.buf = appendTableSize(e.buf, e.minSize)
		}
		e.minSize = uint32Max
		e.buf = appendTableSize(e.buf, e.dynTab.maxSize)
	}

// 查找是否被索引	
    idx, nameValueMatch := e.searchTable(f)
	if nameValueMatch {
		e.buf = appendIndexed(e.buf, idx)
	} else {
// 是否应该被索引，有可能设置一些敏感词不应该被索引，golang indexing 一直是true		
        indexing := e.shouldIndex(f)
		if indexing {
			e.dynTab.add(f)     // 加入动态表		
   	 	}

		if idx == 0 {
			e.buf = appendNewName(e.buf, f, indexing)
		} else {
			e.buf = appendIndexedName(e.buf, f, idx, indexing)
		}
	}
	n, err := e.w.Write(e.buf)
	if err == nil && n != len(e.buf) {
		err = io.ErrShortWrite
	}
	return err
}

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func (e *Encoder) searchTable(f HeaderField) (i uint64, nameValueMatch bool) {
	i, nameValueMatch = staticTable.search(f)
	if nameValueMatch {
		return i, true
	}

	j, nameValueMatch := e.dynTab.table.search(f)
	if nameValueMatch || (i == 0 && j != 0) {
		return j + uint64(staticTable.len()), nameValueMatch
	}

	return i, false
}

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func appendIndexed(dst []byte, i uint64) []byte {
	first := len(dst)
	dst = appendVarInt(dst, 7, i)
	dst[first] |= 0x80
	return dst
}

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func (dt *dynamicTable) add(f HeaderField) {
	dt.table.addEntry(f)
	dt.size += f.Size()
	dt.evict()
}

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func appendNewName(dst []byte, f HeaderField, indexing bool) []byte {
	dst = append(dst, encodeTypeByte(indexing, f.Sensitive)) // 返回0x40 
    dst = appendHpackString(dst, f.Name)
	return appendHpackString(dst, f.Value)
}

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func appendIndexedName(dst []byte, f HeaderField, i uint64, indexing bool) []byte {
	first := len(dst)
	var n byte
	if indexing {   // 是否应该被索引		
        n = 6
	} else {
		n = 4
	}
	dst = appendVarInt(dst, n, i)
	dst[first] |= encodeTypeByte(indexing, f.Sensitive)
	return appendHpackString(dst, f.Value)
}

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func appendHpackString(dst []byte, s string) []byte {
	huffmanLength := HuffmanEncodeLength(s)
	if huffmanLength < uint64(len(s)) {
		first := len(dst)
		dst = appendVarInt(dst, 7, huffmanLength)
		dst = AppendHuffmanString(dst, s)
		dst[first] |= 0x80
	} else {
		dst = appendVarInt(dst, 7, uint64(len(s)))
		dst = append(dst, s...)
	}
	return dst
}

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func appendByteToHuffmanCode(dst []byte, rembits uint8, c byte) ([]byte, uint8) {
	code := huffmanCodes[c]
	nbits := huffmanCodeLen[c]

	for {
		if rembits > nbits {
			t := uint8(code << (rembits - nbits))
			dst[len(dst)-1] |= t
			rembits -= nbits
			break
		}

		t := uint8(code >> (nbits - rembits))
		dst[len(dst)-1] |= t

		nbits -= rembits
		rembits = 8

		if nbits == 0 {
			break
		}

		dst = append(dst, 0)
	}

	return dst, rembits
}



var huffmanCodes = [256]uint32{
	0x1ff8,
	0x7fffd8,
	0xfffffe2,
	0xfffffe3,
	0xfffffe4,
    ....
}


var huffmanCodeLen = [256]uint8{
	13, 23, 28, 28, 28, 28, 28, 28, 28, 24, 30, 28, 28, 30, 28, 28,
	28, 28, 28, 28, 28, 28, 30, 28, 28, 28, 28, 28, 28, 28, 28, 28,
    ...
}

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var (
  buf     bytes.Buffer
  oriSize int
)
henc := hpack.NewEncoder(&buf)
headers := []hpack.HeaderField{
  {Name: ":authority", Value: "dss0.bdstatic.com"},
  {Name: ":method", Value: "GET"},
  {Name: ":path", Value: "/5aV1bjqh_Q23odCf/static/superman/img/topnav/baiduyun@2x-e0be79e69e.png"},
  {Name: ":scheme", Value: "https"},
  {Name: "accept-encoding", Value: "gzip"},
  {Name: "user-agent", Value: "Go-http-client/2.0"},
  {Name: "custom-header", Value: "custom-value"},
}
for _, header := range headers {
  oriSize += len(header.Name) + len(header.Value)
  henc.WriteField(header)
}
fmt.Printf("ori size: %v, encoded size: %v\n", oriSize, buf.Len())
//输出为：ori size: 197, encoded size: 111

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// 此处省略HPACK编码中的编码例子
var (
  invalid    error
  sawRegular bool
  // 16 << 20 from fr.maxHeaderListSize() from
  remainSize uint32 = 16 << 20
)
hdec := hpack.NewDecoder(4096, nil)
// 16 << 20 from fr.maxHeaderStringLen() from fr.maxHeaderListSize()
hdec.SetMaxStringLength(int(remainSize))
hdec.SetEmitFunc(func(hf hpack.HeaderField) {
  if !httpguts.ValidHeaderFieldValue(hf.Value) {
    invalid = fmt.Errorf("invalid header field value %q", hf.Value)
  }
  isPseudo := strings.HasPrefix(hf.Name, ":")
  if isPseudo {
    if sawRegular {
      invalid = errors.New("pseudo header field after regular")
    }
  } else {
    sawRegular = true
    // if !http2validWireHeaderFieldName(hf.Name) {
    // 	invliad = fmt.Sprintf("invalid header field name %q", hf.Name)
    // }
  }
  if invalid != nil {
    fmt.Println(invalid)
    hdec.SetEmitEnabled(false)
    return
  }
  size := hf.Size()
  if size > remainSize {
    hdec.SetEmitEnabled(false)
    // mh.Truncated = true
    return
  }
  remainSize -= size
  fmt.Printf("%+v\n", hf)
  // mh.Fields = append(mh.Fields, hf)
})
defer hdec.SetEmitFunc(func(hf hpack.HeaderField) {})
fmt.Println(hdec.Write(buf.Bytes()))
// 输出如下：
// ori size: 197, encoded size: 111
// header field ":authority" = "dss0.bdstatic.com"
// header field ":method" = "GET"
// header field ":path" = "/5aV1bjqh_Q23odCf/static/superman/img/topnav/baiduyun@2x-e0be79e69e.png"
// header field ":scheme" = "https"
// header field "accept-encoding" = "gzip"
// header field "user-agent" = "Go-http-client/2.0"
// header field "custom-header" = "custom-value"
// 111 <nil>