mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-11-23 14:01:35 +00:00
252 lines
7.1 KiB
Go
252 lines
7.1 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package hpack
|
|
|
|
import (
|
|
"io"
|
|
)
|
|
|
|
const (
|
|
uint32Max = ^uint32(0)
|
|
initialHeaderTableSize = 4096
|
|
)
|
|
|
|
type Encoder struct {
|
|
dynTab dynamicTable
|
|
// minSize is the minimum table size set by
|
|
// SetMaxDynamicTableSize after the previous Header Table Size
|
|
// Update.
|
|
minSize uint32
|
|
// maxSizeLimit is the maximum table size this encoder
|
|
// supports. This will protect the encoder from too large
|
|
// size.
|
|
maxSizeLimit uint32
|
|
// tableSizeUpdate indicates whether "Header Table Size
|
|
// Update" is required.
|
|
tableSizeUpdate bool
|
|
w io.Writer
|
|
buf []byte
|
|
}
|
|
|
|
// NewEncoder returns a new Encoder which performs HPACK encoding. An
|
|
// encoded data is written to w.
|
|
func NewEncoder(w io.Writer) *Encoder {
|
|
e := &Encoder{
|
|
minSize: uint32Max,
|
|
maxSizeLimit: initialHeaderTableSize,
|
|
tableSizeUpdate: false,
|
|
w: w,
|
|
}
|
|
e.dynTab.setMaxSize(initialHeaderTableSize)
|
|
return e
|
|
}
|
|
|
|
// 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]
|
|
|
|
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)
|
|
}
|
|
|
|
idx, nameValueMatch := e.searchTable(f)
|
|
if nameValueMatch {
|
|
e.buf = appendIndexed(e.buf, idx)
|
|
} else {
|
|
indexing := e.shouldIndex(f)
|
|
if indexing {
|
|
e.dynTab.add(f)
|
|
}
|
|
|
|
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
|
|
}
|
|
|
|
// searchTable searches f in both stable and dynamic header tables.
|
|
// The static header table is searched first. Only when there is no
|
|
// exact match for both name and value, the dynamic header table is
|
|
// then searched. If there is no match, i is 0. If both name and value
|
|
// match, i is the matched index and nameValueMatch becomes true. If
|
|
// only name matches, i points to that index and nameValueMatch
|
|
// becomes false.
|
|
func (e *Encoder) searchTable(f HeaderField) (i uint64, nameValueMatch bool) {
|
|
for idx, hf := range staticTable {
|
|
if !constantTimeStringCompare(hf.Name, f.Name) {
|
|
continue
|
|
}
|
|
if i == 0 {
|
|
i = uint64(idx + 1)
|
|
}
|
|
if f.Sensitive {
|
|
continue
|
|
}
|
|
if !constantTimeStringCompare(hf.Value, f.Value) {
|
|
continue
|
|
}
|
|
i = uint64(idx + 1)
|
|
nameValueMatch = true
|
|
return
|
|
}
|
|
|
|
j, nameValueMatch := e.dynTab.search(f)
|
|
if nameValueMatch || (i == 0 && j != 0) {
|
|
i = j + uint64(len(staticTable))
|
|
}
|
|
return
|
|
}
|
|
|
|
// SetMaxDynamicTableSize changes the dynamic header table size to v.
|
|
// The actual size is bounded by the value passed to
|
|
// SetMaxDynamicTableSizeLimit.
|
|
func (e *Encoder) SetMaxDynamicTableSize(v uint32) {
|
|
if v > e.maxSizeLimit {
|
|
v = e.maxSizeLimit
|
|
}
|
|
if v < e.minSize {
|
|
e.minSize = v
|
|
}
|
|
e.tableSizeUpdate = true
|
|
e.dynTab.setMaxSize(v)
|
|
}
|
|
|
|
// SetMaxDynamicTableSizeLimit changes the maximum value that can be
|
|
// specified in SetMaxDynamicTableSize to v. By default, it is set to
|
|
// 4096, which is the same size of the default dynamic header table
|
|
// size described in HPACK specification. If the current maximum
|
|
// dynamic header table size is strictly greater than v, "Header Table
|
|
// Size Update" will be done in the next WriteField call and the
|
|
// maximum dynamic header table size is truncated to v.
|
|
func (e *Encoder) SetMaxDynamicTableSizeLimit(v uint32) {
|
|
e.maxSizeLimit = v
|
|
if e.dynTab.maxSize > v {
|
|
e.tableSizeUpdate = true
|
|
e.dynTab.setMaxSize(v)
|
|
}
|
|
}
|
|
|
|
// shouldIndex reports whether f should be indexed.
|
|
func (e *Encoder) shouldIndex(f HeaderField) bool {
|
|
return !f.Sensitive && f.Size() <= e.dynTab.maxSize
|
|
}
|
|
|
|
// appendIndexed appends index i, as encoded in "Indexed Header Field"
|
|
// representation, to dst and returns the extended buffer.
|
|
func appendIndexed(dst []byte, i uint64) []byte {
|
|
first := len(dst)
|
|
dst = appendVarInt(dst, 7, i)
|
|
dst[first] |= 0x80
|
|
return dst
|
|
}
|
|
|
|
// appendNewName appends f, as encoded in one of "Literal Header field
|
|
// - New Name" representation variants, to dst and returns the
|
|
// extended buffer.
|
|
//
|
|
// If f.Sensitive is true, "Never Indexed" representation is used. If
|
|
// f.Sensitive is false and indexing is true, "Inremental Indexing"
|
|
// representation is used.
|
|
func appendNewName(dst []byte, f HeaderField, indexing bool) []byte {
|
|
dst = append(dst, encodeTypeByte(indexing, f.Sensitive))
|
|
dst = appendHpackString(dst, f.Name)
|
|
return appendHpackString(dst, f.Value)
|
|
}
|
|
|
|
// appendIndexedName appends f and index i referring indexed name
|
|
// entry, as encoded in one of "Literal Header field - Indexed Name"
|
|
// representation variants, to dst and returns the extended buffer.
|
|
//
|
|
// If f.Sensitive is true, "Never Indexed" representation is used. If
|
|
// f.Sensitive is false and indexing is true, "Incremental Indexing"
|
|
// representation is used.
|
|
func appendIndexedName(dst []byte, f HeaderField, i uint64, indexing bool) []byte {
|
|
first := len(dst)
|
|
var n byte
|
|
if indexing {
|
|
n = 6
|
|
} else {
|
|
n = 4
|
|
}
|
|
dst = appendVarInt(dst, n, i)
|
|
dst[first] |= encodeTypeByte(indexing, f.Sensitive)
|
|
return appendHpackString(dst, f.Value)
|
|
}
|
|
|
|
// appendTableSize appends v, as encoded in "Header Table Size Update"
|
|
// representation, to dst and returns the extended buffer.
|
|
func appendTableSize(dst []byte, v uint32) []byte {
|
|
first := len(dst)
|
|
dst = appendVarInt(dst, 5, uint64(v))
|
|
dst[first] |= 0x20
|
|
return dst
|
|
}
|
|
|
|
// appendVarInt appends i, as encoded in variable integer form using n
|
|
// bit prefix, to dst and returns the extended buffer.
|
|
//
|
|
// See
|
|
// http://http2.github.io/http2-spec/compression.html#integer.representation
|
|
func appendVarInt(dst []byte, n byte, i uint64) []byte {
|
|
k := uint64((1 << n) - 1)
|
|
if i < k {
|
|
return append(dst, byte(i))
|
|
}
|
|
dst = append(dst, byte(k))
|
|
i -= k
|
|
for ; i >= 128; i >>= 7 {
|
|
dst = append(dst, byte(0x80|(i&0x7f)))
|
|
}
|
|
return append(dst, byte(i))
|
|
}
|
|
|
|
// appendHpackString appends s, as encoded in "String Literal"
|
|
// representation, to dst and returns the the extended buffer.
|
|
//
|
|
// s will be encoded in Huffman codes only when it produces strictly
|
|
// shorter byte string.
|
|
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
|
|
}
|
|
|
|
// encodeTypeByte returns type byte. If sensitive is true, type byte
|
|
// for "Never Indexed" representation is returned. If sensitive is
|
|
// false and indexing is true, type byte for "Incremental Indexing"
|
|
// representation is returned. Otherwise, type byte for "Without
|
|
// Indexing" is returned.
|
|
func encodeTypeByte(indexing, sensitive bool) byte {
|
|
if sensitive {
|
|
return 0x10
|
|
}
|
|
if indexing {
|
|
return 0x40
|
|
}
|
|
return 0
|
|
}
|