mirror of https://bitbucket.org/ausocean/av.git
305 lines
6.9 KiB
Go
305 lines
6.9 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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const (
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PacketSize = 184 // packet size of a psi.
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)
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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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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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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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// Other misc consts
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const (
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syntaxSecLenIndx = 3
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crcSize = 4
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)
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const (
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SectionLenIdx1 = 2
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SectionLenIdx2 = 3
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)
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const (
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SectionLenMask1 = 0x03
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)
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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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const (
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DescriptorsIdx = ProgramInfoLenIdx2 + 1
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)
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const MetadataTag = 0x26
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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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out = addPadding(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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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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desc := p.HasDescriptor(tag)
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if desc == nil {
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p.createDescriptor(tag, data)
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return nil
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}
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desc.update(data)
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return nil
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}
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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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func (p *PSIBytes) HasDescriptor(tag int) Descriptor {
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descs := p.descriptors()
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if descs == nil {
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return 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 descs[i : i+2+int(descs[i+1])]
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}
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}
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return nil
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}
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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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func (p *PSIBytes) createDescriptor(tag int, data []byte) {
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curProgLen := p.ProgramInfoLen()
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dataLen := len(data)
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// Calculate the new descriptors index and length.
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newDescIdx := DescriptorsIdx + curProgLen
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newDescLen := dataLen + 2
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// Copy data down from newDescIdx to create room for the new descriptor.
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copy((*p)[newDescIdx+newDescLen:], (*p)[newDescIdx:dataLen-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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// Update the program info length to account for the new descriptor.
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newProgInfoLen := curProgLen + dataLen
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(*p)[ProgramInfoLenIdx1] = byte(newProgInfoLen >> 8)
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(*p)[ProgramInfoLenIdx2] = byte(newProgInfoLen)
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}
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func (d *Descriptor) update(data []byte) {
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if len(data) > int((*d)[1]) {
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// TODO: implement resizing of descriptor
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panic("Can't resize descriptor data")
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}
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}
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