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Simplify VLP-16 packet parsing
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The reason for this change is to enable an easy way to produce mock
VLP-16 serialized data in tests, using a single call to binary.Write.

However, this change also ensures that the Packet struct models
byte-for-byte an on-the-wire VLP-16 packet, which simplifies parsing to
a single binary.Read call.
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@odsod
odsod committed Nov 8, 2018
1 parent f922b62 commit bc6596d
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Showing 2 changed files with 55 additions and 76 deletions.
49 changes: 7 additions & 42 deletions pkg/vlp16/packet.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ type Packet struct {
}

type Block struct {
Flag uint16
Azimuth uint16
Channels [32]Channel
}
Expand All @@ -23,6 +24,7 @@ type Channel struct {
Distance uint16
Reflectivity Reflectivity
}

type Reflectivity uint8

type ReturnMode uint8
Expand All @@ -46,51 +48,14 @@ const (
)

func (p *Packet) Read(r io.Reader) error {
// Read 12 blocks
for i := 0; i < len(p.Blocks); i++ {
if err := p.Blocks[i].Read(r); err != nil {
return err
}
}
// Read timestamp
if err := binary.Read(r, binary.LittleEndian, &p.Timestamp); err != nil {
return err
}
// Read factory flags
if err := binary.Read(r, binary.LittleEndian, &p.ReturnMode); err != nil {
return err
}
if err := binary.Read(r, binary.LittleEndian, &p.ProductID); err != nil {
return err
}
return nil
}

func (b *Block) Read(r io.Reader) error {
var flag uint16
if err := binary.Read(r, binary.LittleEndian, &flag); err != nil {
return err
}
if flag != 0xeeff {
return errors.Errorf("unexpected flag: %v", flag)
}
if err := binary.Read(r, binary.LittleEndian, &b.Azimuth); err != nil {
if err := binary.Read(r, binary.LittleEndian, p); err != nil {
return err
}
for i := 0; i < len(b.Channels); i++ {
if err := b.Channels[i].Read(r); err != nil {
return err
// validate flags
for i := 0; i < len(p.Blocks); i++ {
if p.Blocks[i].Flag != 0xeeff {
return errors.Errorf("invalid flag value %v in block %v", p.Blocks[i].Flag, i)
}
}
return nil
}

func (c *Channel) Read(r io.Reader) error {
if err := binary.Read(r, binary.LittleEndian, &c.Distance); err != nil {
return err
}
if err := binary.Read(r, binary.LittleEndian, &c.Reflectivity); err != nil {
return err
}
return nil
}
82 changes: 48 additions & 34 deletions pkg/vlp16/packet_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ var examplePacket = vlp16.Packet{
Blocks: [12]vlp16.Block{
{
Azimuth: 0x2866,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x2ff, Reflectivity: 0x3},
Expand Down Expand Up @@ -92,6 +93,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x288e,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x0, Reflectivity: 0x64},
Expand Down Expand Up @@ -129,6 +131,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x28b6,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x31c, Reflectivity: 0x45},
Expand Down Expand Up @@ -166,6 +169,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x28de,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x321, Reflectivity: 0x41},
Expand Down Expand Up @@ -203,6 +207,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x2906,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x322, Reflectivity: 0x43},
Expand Down Expand Up @@ -238,43 +243,47 @@ var examplePacket = vlp16.Packet{
{Distance: 0x2d7, Reflectivity: 0x3b},
},
},
{Azimuth: 0x292e, Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x32b, Reflectivity: 0x41},
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x324, Reflectivity: 0x4b},
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x2bf, Reflectivity: 0x40},
{Distance: 0x0, Reflectivity: 0x3},
{Distance: 0x2c0, Reflectivity: 0x3f},
{Distance: 0x0, Reflectivity: 0x1},
{Distance: 0x2c3, Reflectivity: 0x41},
{Distance: 0x2d1, Reflectivity: 0x2a},
{Distance: 0x2ca, Reflectivity: 0x3c},
{Distance: 0x2c4, Reflectivity: 0x43},
{Distance: 0x2cd, Reflectivity: 0x35},
{Distance: 0x318, Reflectivity: 0x3b},
{Distance: 0x2dd, Reflectivity: 0x35},
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x32f, Reflectivity: 0x3d},
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x326, Reflectivity: 0x4c},
{Distance: 0x0, Reflectivity: 0x4},
{Distance: 0x2be, Reflectivity: 0x3b},
{Distance: 0x0, Reflectivity: 0x3},
{Distance: 0x2c6, Reflectivity: 0x35},
{Distance: 0x0, Reflectivity: 0x1},
{Distance: 0x2c5, Reflectivity: 0x3c},
{Distance: 0x2d1, Reflectivity: 0x2d},
{Distance: 0x2cc, Reflectivity: 0x3c},
{Distance: 0x2ca, Reflectivity: 0x43},
{Distance: 0x2cf, Reflectivity: 0x31},
{Distance: 0x310, Reflectivity: 0x12},
{Distance: 0x2da, Reflectivity: 0x30},
},
{
Azimuth: 0x292e,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x32b, Reflectivity: 0x41},
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x324, Reflectivity: 0x4b},
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x2bf, Reflectivity: 0x40},
{Distance: 0x0, Reflectivity: 0x3},
{Distance: 0x2c0, Reflectivity: 0x3f},
{Distance: 0x0, Reflectivity: 0x1},
{Distance: 0x2c3, Reflectivity: 0x41},
{Distance: 0x2d1, Reflectivity: 0x2a},
{Distance: 0x2ca, Reflectivity: 0x3c},
{Distance: 0x2c4, Reflectivity: 0x43},
{Distance: 0x2cd, Reflectivity: 0x35},
{Distance: 0x318, Reflectivity: 0x3b},
{Distance: 0x2dd, Reflectivity: 0x35},
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x32f, Reflectivity: 0x3d},
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x326, Reflectivity: 0x4c},
{Distance: 0x0, Reflectivity: 0x4},
{Distance: 0x2be, Reflectivity: 0x3b},
{Distance: 0x0, Reflectivity: 0x3},
{Distance: 0x2c6, Reflectivity: 0x35},
{Distance: 0x0, Reflectivity: 0x1},
{Distance: 0x2c5, Reflectivity: 0x3c},
{Distance: 0x2d1, Reflectivity: 0x2d},
{Distance: 0x2cc, Reflectivity: 0x3c},
{Distance: 0x2ca, Reflectivity: 0x43},
{Distance: 0x2cf, Reflectivity: 0x31},
{Distance: 0x310, Reflectivity: 0x12},
{Distance: 0x2da, Reflectivity: 0x30},
},
},
{
Azimuth: 0x2956,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x331, Reflectivity: 0x3d},
Expand Down Expand Up @@ -312,6 +321,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x297d,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x333, Reflectivity: 0x3d},
Expand Down Expand Up @@ -349,6 +359,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x29a5,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x33a, Reflectivity: 0x38},
Expand Down Expand Up @@ -386,6 +397,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x29cc,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x339, Reflectivity: 0x3c},
Expand Down Expand Up @@ -423,6 +435,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x29f5,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x344, Reflectivity: 0x3a},
Expand Down Expand Up @@ -460,6 +473,7 @@ var examplePacket = vlp16.Packet{
},
{
Azimuth: 0x2a1d,
Flag: 0xeeff,
Channels: [32]vlp16.Channel{
{Distance: 0x0, Reflectivity: 0x2},
{Distance: 0x346, Reflectivity: 0x38},
Expand Down

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