mirror of https://bitbucket.org/ausocean/av.git
371 lines
9.9 KiB
Go
371 lines
9.9 KiB
Go
/*
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NAME
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psi.go
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DESCRIPTION
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See Readme.md
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AUTHOR
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Saxon Milton <saxon@ausocean.org>
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LICENSE
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psi.go is Copyright (C) 2018 the Australian Ocean Lab (AusOcean)
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with revid in gpl.txt. If not, see http://www.gnu.org/licenses.
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*/
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package psi
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import (
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"errors"
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"github.com/Comcast/gots/psi"
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)
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// PacketSize of psi (without MPEG-TS header)
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const PacketSize = 184
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// Lengths of section definitions.
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const (
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ESSDDefLen = 5
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DescDefLen = 2
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PMTDefLen = 4
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PATLen = 4
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TSSDefLen = 5
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PSIDefLen = 3
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)
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// Table Type IDs.
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const (
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patID = 0x00
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pmtID = 0x02
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)
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// Consts relating to time description
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// TODO: remove this, we don't do metadata like this anymore.
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const (
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TimeDescTag = 234
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TimeTagIndx = 13
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TimeDataIndx = 15
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TimeDataSize = 8 // bytes, because time is stored in uint64
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)
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// Consts relating to location description
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// TODO: remove this, we don't do metadata like this anymore.
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const (
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LocationDescTag = 235
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LocationTagIndx = 23
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LocationDataIndx = 25
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LocationDataSize = 32 // bytes
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)
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// crc hassh Size
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const crcSize = 4
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// Consts relating to syntax section.
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const (
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TotalSyntaxSecLen = 180
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SyntaxSecLenIdx1 = 2
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SyntaxSecLenIdx2 = 3
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SyntaxSecLenMask1 = 0x03
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SectionLenMask1 = 0x03
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)
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// Consts relating to program info len.
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const (
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ProgramInfoLenIdx1 = 11
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ProgramInfoLenIdx2 = 12
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ProgramInfoLenMask1 = 0x03
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)
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// DescriptorsIdx is the index that the descriptors start at.
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const DescriptorsIdx = ProgramInfoLenIdx2 + 1
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// MetadataTag is the descriptor tag used for metadata.
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const MetadataTag = 0x26
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// TODO: get rid of these - not a good idea.
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type (
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PSIBytes []byte
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Descriptor []byte
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)
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// Program specific information
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type PSI struct {
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Pf byte // Point field
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Pfb []byte // Pointer filler bytes
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Tid byte // Table ID
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Ssi bool // Section syntax indicator (1 for PAT, PMT, CAT)
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Pb bool // Private bit (0 for PAT, PMT, CAT)
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Sl uint16 // Section length
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Tss *TSS // Table syntax section (length defined by SL) if length 0 then nil
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Crc uint32 // crc32 of entire table excluding pointer field, pointer filler bytes and the trailing CRC32
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}
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// Table syntax section
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type TSS struct {
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Tide uint16 // Table ID extension
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V byte // Version number
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Cni bool // Current/next indicator
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Sn byte // Section number
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Lsn byte // Last section number
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Sd SpecificData // Specific data PAT/PMT
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}
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// Specific Data, (could be PAT or PMT)
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type SpecificData interface {
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Bytes() []byte
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}
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// Program association table, implements SpecificData
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type PAT struct {
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Pn uint16 // Program Number
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Pmpid uint16 // Program map PID
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}
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// Program mapping table, implements SpecificData
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type PMT struct {
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Pcrpid uint16 // Program clock reference pid
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Pil uint16 // Program info length
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Pd []Desc // Program descriptors
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Essd *ESSD // Elementary stream specific data
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}
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// Elementary stream specific data
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type ESSD struct {
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St byte // Stream type
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Epid uint16 // Elementary pid
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Esil uint16 // Elementary stream
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Esd []Desc // Elementary stream desriptors
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}
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// Descriptor
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type Desc struct {
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Dt byte // Descriptor tag
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Dl byte // Descriptor length
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Dd []byte // Descriptor data
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}
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// Bytes outputs a byte slice representation of the PSI
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func (p *PSI) Bytes() []byte {
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out := make([]byte, 4)
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out[0] = p.Pf
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if p.Pf != 0 {
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panic("No support for pointer filler bytes")
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}
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out[1] = p.Tid
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out[2] = 0x80 | 0x30 | (0x03 & byte(p.Sl>>8))
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out[3] = byte(p.Sl)
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out = append(out, p.Tss.Bytes()...)
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out = AddCrc(out)
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return out
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}
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// Bytes outputs a byte slice representation of the TSS
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func (t *TSS) Bytes() []byte {
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out := make([]byte, TSSDefLen)
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out[0] = byte(t.Tide >> 8)
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out[1] = byte(t.Tide)
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out[2] = 0xc0 | (0x3e & (t.V << 1)) | (0x01 & asByte(t.Cni))
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out[3] = t.Sn
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out[4] = t.Lsn
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out = append(out, t.Sd.Bytes()...)
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return out
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}
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// Bytes outputs a byte slice representation of the PAT
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func (p *PAT) Bytes() []byte {
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out := make([]byte, PATLen)
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out[0] = byte(p.Pn >> 8)
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out[1] = byte(p.Pn)
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out[2] = 0xe0 | (0x1f & byte(p.Pmpid>>8))
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out[3] = byte(p.Pmpid)
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return out
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}
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// Bytes outputs a byte slice representation of the PMT
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func (p *PMT) Bytes() []byte {
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out := make([]byte, PMTDefLen)
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out[0] = 0xe0 | (0x1f & byte(p.Pcrpid>>8)) // byte 10
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out[1] = byte(p.Pcrpid)
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out[2] = 0xf0 | (0x03 & byte(p.Pil>>8))
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out[3] = byte(p.Pil)
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for _, d := range p.Pd {
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out = append(out, d.Bytes()...)
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}
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out = append(out, p.Essd.Bytes()...)
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return out
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}
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// Bytes outputs a byte slice representation of the Desc
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func (d *Desc) Bytes() []byte {
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out := make([]byte, DescDefLen)
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out[0] = d.Dt
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out[1] = d.Dl
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out = append(out, d.Dd...)
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return out
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}
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// Bytes outputs a byte slice representation of the ESSD
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func (e *ESSD) Bytes() []byte {
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out := make([]byte, ESSDDefLen)
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out[0] = e.St
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out[1] = 0xe0 | (0x1f & byte(e.Epid>>8))
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out[2] = byte(e.Epid)
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out[3] = 0xf0 | (0x03 & byte(e.Esil>>8))
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out[4] = byte(e.Esil)
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for _, d := range e.Esd {
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out = append(out, d.Bytes()...)
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}
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return out
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}
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func asByte(b bool) byte {
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if b {
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return 0x01
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}
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return 0x00
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}
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// AddDescriptor adds or updates a descriptor in a PSI given a descriptor tag
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// and data. If the psi is not a pmt, then an error is returned. If a descriptor
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// with the given tag is not found in the psi, room is made and a descriptor with
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// given tag and data is created. If a descriptor with the tag is found, the
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// descriptor is resized as required and the new data is copied in.
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func (p *PSIBytes) AddDescriptor(tag int, data []byte) error {
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if psi.TableID(*p) != pmtID {
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return errors.New("trying to add descriptor, but not pmt")
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}
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i, desc := p.HasDescriptor(tag)
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if desc == nil {
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err := p.createDescriptor(tag, data)
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return err
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}
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oldDescLen := desc.len()
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oldDataLen := int(desc[1])
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newDataLen := len(data)
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newDescLen := 2 + newDataLen
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delta := newDescLen - oldDescLen
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// If the old data length is more than the new data length, we need shift data
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// after descriptor up, and then trim the psi. If the oldDataLen is less than
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// new data then we need reseize psi and shift data down. If same do nothing.
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switch {
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case oldDataLen > newDataLen:
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copy((*p)[i+newDescLen:], (*p)[i+oldDescLen:])
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*p = (*p)[:len(*p)+delta]
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case oldDataLen < newDataLen:
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tmp := make([]byte, len(*p)+delta)
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copy(tmp, *p)
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*p = tmp
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copy((*p)[i+newDescLen:], (*p)[i+oldDescLen:])
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}
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// Copy in new data
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(*p)[i+1] = byte(newDataLen)
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copy((*p)[i+2:], data)
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newProgInfoLen := p.ProgramInfoLen() + delta
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p.setProgInfoLen(newProgInfoLen)
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newSectionLen := int(psi.SectionLength(*p)) + delta
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p.setSectionLen(newSectionLen)
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UpdateCrc((*p)[1:])
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return nil
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}
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// HasDescriptor checks if a descriptor of the given tag exists in a PSI. If the descriptor
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// of the given tag exists, an index of this descriptor, as well as the Descriptor is returned.
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// If the descriptor of the given tag cannot be found, -1 and a nil slice is returned.
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//
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// TODO: check if pmt, return error if not ?
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func (p *PSIBytes) HasDescriptor(tag int) (int, Descriptor) {
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descs := p.descriptors()
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if descs == nil {
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return -1, nil
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}
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for i := 0; i < len(descs); i += 2 + int(descs[i+1]) {
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if int(descs[i]) == tag {
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return i + DescriptorsIdx, descs[i : i+2+int(descs[i+1])]
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}
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}
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return -1, nil
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}
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// createDescriptor creates a descriptor in a psi given a tag and data. It does so
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// by resizing the psi, shifting existing data down and copying in new descriptor
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// in new space.
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func (p *PSIBytes) createDescriptor(tag int, data []byte) error {
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curProgLen := p.ProgramInfoLen()
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oldSyntaxSectionLen := SyntaxSecLenFrom(*p)
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if TotalSyntaxSecLen-(oldSyntaxSectionLen+2+len(data)) <= 0 {
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return errors.New("Not enough space in psi to create descriptor.")
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}
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dataLen := len(data)
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newDescIdx := DescriptorsIdx + curProgLen
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newDescLen := dataLen + 2
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// Increase size of psi and copy data down to make room for new descriptor.
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tmp := make([]byte, len(*p)+newDescLen)
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copy(tmp, *p)
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*p = tmp
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copy((*p)[newDescIdx+newDescLen:], (*p)[newDescIdx:newDescIdx+newDescLen])
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// Set the tag, data len and data of the new desriptor.
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(*p)[newDescIdx] = byte(tag)
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(*p)[newDescIdx+1] = byte(dataLen)
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copy((*p)[newDescIdx+2:newDescIdx+2+dataLen], data)
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// Set length fields and update the psi crc.
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addedLen := dataLen + 2
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newProgInfoLen := curProgLen + addedLen
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p.setProgInfoLen(newProgInfoLen)
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newSyntaxSectionLen := int(oldSyntaxSectionLen) + addedLen
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p.setSectionLen(newSyntaxSectionLen)
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UpdateCrc((*p)[1:])
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return nil
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}
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// setProgInfoLen sets the program information length in a psi with a pmt.
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func (p *PSIBytes) setProgInfoLen(l int) {
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(*p)[ProgramInfoLenIdx1] &= 0xff ^ ProgramInfoLenMask1
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(*p)[ProgramInfoLenIdx1] |= byte(l>>8) & ProgramInfoLenMask1
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(*p)[ProgramInfoLenIdx2] = byte(l)
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}
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// setSectionLen sets section length in a psi.
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func (p *PSIBytes) setSectionLen(l int) {
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(*p)[SyntaxSecLenIdx1] &= 0xff ^ SyntaxSecLenMask1
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(*p)[SyntaxSecLenIdx1] |= byte(l>>8) & SyntaxSecLenMask1
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(*p)[SyntaxSecLenIdx2] = byte(l)
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}
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// descriptors returns the descriptors in a psi if they exist, otherwise
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// a nil slice is returned.
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func (p *PSIBytes) descriptors() []byte {
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return (*p)[DescriptorsIdx : DescriptorsIdx+p.ProgramInfoLen()]
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}
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// len returns the length of a descriptor in bytes.
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func (d *Descriptor) len() int {
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return int(2 + (*d)[1])
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}
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// ProgramInfoLen returns the program info length of a PSI.
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//
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// TODO: check if pmt - if not return 0 ? or -1 ?
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func (p *PSIBytes) ProgramInfoLen() int {
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return int((((*p)[ProgramInfoLenIdx1] & ProgramInfoLenMask1) << 8) | (*p)[ProgramInfoLenIdx2])
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}
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