mirror of
https://github.com/livekit/livekit.git
synced 2026-03-30 22:05:39 +00:00
a05690d2b2
S, F -> Start, Final of frame changed from F, L -> First, Last of frame as `F` could be interpreted as `Final` also.
270 lines
8.4 KiB
Go
270 lines
8.4 KiB
Go
// Copyright 2023 LiveKit, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package datatrack
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import (
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"encoding/binary"
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"errors"
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"fmt"
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)
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var (
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errHeaderSizeInsufficient = errors.New("data track packet header size insufficient")
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errBufferSizeInsufficient = errors.New("data track packet buffer size insufficient")
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errExtensionSizeInsufficient = errors.New("data track packet extension size insufficient")
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errExtensionNotFound = errors.New("data track packet extension not found")
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)
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const (
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headerLength = 12
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versionShift = 5
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versionMask = (1 << 3) - 1
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startOfFrameShift = 4
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startOfFrameMask = (1 << 1) - 1
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finalOfFrameShift = 3
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finalOfFrameMask = (1 << 1) - 1
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extensionsShift = 2
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extensionsMask = (1 << 1) - 1
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handleOffset = 2
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handleLength = 2
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seqNumOffset = 4
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seqNumLength = 2
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frameNumOffset = 6
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frameNumLength = 2
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timestampOffset = 8
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timestampLength = 4
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extensionsSizeOffset = headerLength
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extensionsSizeLength = 2
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extensionIDLength = 2
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extensionSizeLength = 2
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)
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type Extension struct {
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id uint16
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data []byte
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}
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type Header struct {
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Version uint8
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IsStartOfFrame bool
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IsFinalOfFrame bool
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HasExtensions bool
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Handle uint16
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SequenceNumber uint16
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FrameNumber uint16
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Timestamp uint32
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ExtensionsSize uint16
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Extensions []Extension
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}
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/*
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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┆* 0 1 2 3
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┆* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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┆* |V |F|L|X| reserved | handle |
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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┆* | sequence number | frame number |
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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┆* | timestamp |
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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|* Extensions Size if X=1 | Extensions... |
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Each extension
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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┆* 0 1 2 3
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┆* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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┆* | Extension ID | Extension size |
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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|* Extension payload (padded to 4 byte boundary) |
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┆* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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func (h *Header) Unmarshal(buf []byte) (int, error) {
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if len(buf) < headerLength {
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return 0, fmt.Errorf("%w: %d < %d", errHeaderSizeInsufficient, len(buf), headerLength)
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}
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hdrSize := headerLength
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h.Version = buf[0] >> versionShift & versionMask
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h.IsStartOfFrame = (buf[0] >> startOfFrameShift & startOfFrameMask) > 0
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h.IsFinalOfFrame = (buf[0] >> finalOfFrameShift & finalOfFrameMask) > 0
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h.HasExtensions = (buf[0] >> extensionsShift & extensionsMask) > 0
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h.Handle = binary.BigEndian.Uint16(buf[handleOffset : handleOffset+handleLength])
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h.SequenceNumber = binary.BigEndian.Uint16(buf[seqNumOffset : seqNumOffset+seqNumLength])
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h.FrameNumber = binary.BigEndian.Uint16(buf[frameNumOffset : frameNumOffset+frameNumLength])
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h.Timestamp = binary.BigEndian.Uint32(buf[timestampOffset : timestampOffset+timestampLength])
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if h.HasExtensions {
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h.ExtensionsSize = (binary.BigEndian.Uint16(buf[extensionsSizeOffset:extensionsSizeOffset+extensionsSizeLength]) + 1) * 4
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hdrSize += extensionsSizeLength
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remainingSize := int(h.ExtensionsSize)
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idx := extensionsSizeOffset + extensionsSizeLength
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for remainingSize != 0 {
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if len(buf[idx:]) < 4 || remainingSize < 4 {
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return 0, fmt.Errorf("%w: %d/%d < %d", errExtensionSizeInsufficient, remainingSize, len(buf[idx:]), 4)
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}
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id := binary.BigEndian.Uint16(buf[idx : idx+2])
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size := int(binary.BigEndian.Uint16(buf[idx+2 : idx+4]))
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remainingSize -= 4
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idx += 4
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hdrSize += 4
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if len(buf[idx:]) < size || remainingSize < size {
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return 0, fmt.Errorf("%w: %d/%d < %d", errExtensionSizeInsufficient, remainingSize, len(buf[idx:]), size)
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}
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h.Extensions = append(h.Extensions, Extension{id: id, data: buf[idx : idx+size]})
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size = ((size + 3) / 4) * 4
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remainingSize -= size
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idx += size
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hdrSize += size
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}
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}
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return hdrSize, nil
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}
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func (h *Header) MarshalSize() int {
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size := headerLength
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if h.HasExtensions {
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size += 2 // extensions size field
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for _, ext := range h.Extensions {
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size += ((len(ext.data)+3)/4)*4 + 2 /* extension ID field */ + 2 /* extension length field */
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}
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}
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return size
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}
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func (h *Header) MarshalTo(buf []byte) (int, error) {
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if len(buf) < headerLength {
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return 0, fmt.Errorf("%w: %d < %d", errHeaderSizeInsufficient, len(buf), headerLength)
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}
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hdrSize := headerLength
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buf[0] = h.Version << versionShift
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if h.IsStartOfFrame {
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buf[0] |= (1 << startOfFrameShift)
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}
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if h.IsFinalOfFrame {
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buf[0] |= (1 << finalOfFrameShift)
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}
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if h.HasExtensions {
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buf[0] |= (1 << extensionsShift)
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}
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binary.BigEndian.PutUint16(buf[handleOffset:handleOffset+handleLength], h.Handle)
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binary.BigEndian.PutUint16(buf[seqNumOffset:seqNumOffset+seqNumLength], h.SequenceNumber)
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binary.BigEndian.PutUint16(buf[frameNumOffset:frameNumOffset+frameNumLength], h.FrameNumber)
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binary.BigEndian.PutUint32(buf[timestampOffset:timestampOffset+timestampLength], h.Timestamp)
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if h.HasExtensions {
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binary.BigEndian.PutUint16(buf[extensionsSizeOffset:extensionsSizeOffset+extensionsSizeLength], (h.ExtensionsSize/4)-1)
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hdrSize += extensionsSizeLength
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idx := extensionsSizeOffset + extensionsSizeLength
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for _, ext := range h.Extensions {
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binary.BigEndian.PutUint16(buf[idx:idx+extensionIDLength], ext.id)
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binary.BigEndian.PutUint16(buf[idx+extensionIDLength:idx+extensionIDLength+extensionSizeLength], uint16(len(ext.data)))
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copy(buf[idx+extensionIDLength+extensionSizeLength:], ext.data)
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idx += ((len(ext.data)+3)/4)*4 + 2 /* extension ID field */ + 2 /* extension length field */
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hdrSize += ((len(ext.data)+3)/4)*4 + 2 /* extension ID field */ + 2 /* extension length field */
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}
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}
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return hdrSize, nil
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}
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func (h *Header) AddExtension(ext Extension) {
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for i, existingExt := range h.Extensions {
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if existingExt.id == ext.id {
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h.ExtensionsSize -= uint16((len(existingExt.data)+3)/4*4 + 2 /* extension ID field */ + 2 /* extension length field */)
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h.Extensions[i].data = ext.data
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h.ExtensionsSize += uint16((len(h.Extensions[i].data)+3)/4*4 + 2 /* extension ID field */ + 2 /* extension length field */)
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return
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}
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}
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h.Extensions = append(h.Extensions, ext)
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h.ExtensionsSize += uint16((len(ext.data)+3)/4*4 + 2 /* extension ID field */ + 2 /* extension length field */)
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h.HasExtensions = true
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}
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func (h *Header) GetExtension(id uint16) (Extension, error) {
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for _, ext := range h.Extensions {
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if ext.id == id {
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return ext, nil
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}
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}
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return Extension{}, fmt.Errorf("%w, id: %d", errExtensionNotFound, id)
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}
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// ----------------------------------------------------
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type Packet struct {
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Header
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Payload []byte
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}
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func (p *Packet) Unmarshal(buf []byte) error {
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hdrSize, err := p.Header.Unmarshal(buf)
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if err != nil {
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return err
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}
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p.Payload = buf[hdrSize:]
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return nil
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}
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func (p *Packet) Marshal() ([]byte, error) {
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buf := make([]byte, p.Header.MarshalSize()+len(p.Payload))
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if err := p.MarshalTo(buf); err != nil {
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return nil, err
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}
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return buf, nil
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}
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func (p *Packet) MarshalTo(buf []byte) error {
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size := p.Header.MarshalSize() + len(p.Payload)
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if len(buf) < size {
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return fmt.Errorf("%w: %d < %d", errBufferSizeInsufficient, len(buf), size)
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}
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hdrSize, err := p.Header.MarshalTo(buf)
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if err != nil {
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return err
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}
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copy(buf[hdrSize:], p.Payload)
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return nil
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}
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