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modulation.go
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modulation.go
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package transmission
import (
"crypto/sha1"
"encoding/hex"
"fmt"
"math"
"strconv"
"github.com/Hunter-Dolan/midrange/modulation"
"github.com/Hunter-Dolan/midrange/options"
"github.com/Hunter-Dolan/midrange/utils"
)
func (t *Transmission) SetData(data string) {
dataBytes := []byte(data)
dataBytes = compress(dataBytes)
t.dataLength = len(dataBytes) * 8
t.originalDataLength = len(data) * 8
packetCount := math.Ceil(float64(t.dataLength) / float64(options.PacketDataLength))
t.data = make([]*packet, int(packetCount))
for packetIndex := range t.data {
p := packet{}
leftEnd := int(packetIndex * options.PacketDataLengthBytes)
rightEnd := int(leftEnd + options.PacketDataLengthBytes)
if rightEnd > len(dataBytes) {
rightEnd = len(dataBytes)
}
p.setBytes(dataBytes[leftEnd:rightEnd])
t.data[packetIndex] = &p
}
t.generateHeaderPacket()
}
func (t *Transmission) generateHeaderPacket() {
dataLengthBin, dataLengthBool := t.dataLengthBin()
checksumBin, checksumBool := t.checksumBin()
bytes := []byte((dataLengthBin + checksumBin)[:])
bin := append(dataLengthBool, checksumBool...)
p := packet{}
p.data = &bin
p.calculateHash(bytes)
p.replicateHash(options.HeaderChecksumRedundancy)
t.header = &p
}
func (t *Transmission) checksumBin() (string, []bool) {
checksum := []byte{}
for _, packet := range t.data {
checksum = append(checksum, packet.hashBytes...)
}
checksumBin := utils.BinEncode(checksum)
checksumBinByte := utils.BoolToByteBin(checksumBin)
sha1DataFull := sha1.Sum(checksumBinByte)
sha1Data := sha1DataFull[:options.HeaderTransmissionChecksumLength/8]
sha1Int, _ := strconv.ParseInt(hex.EncodeToString(sha1Data), 16, 64)
sha1Bin := strconv.FormatInt(sha1Int, 2)
sha1Bin = utils.LeftPad(sha1Bin, options.HeaderTransmissionChecksumLength)
sha1Dec := strconv.FormatInt(sha1Int, 10)
fmt.Println("Transmission Hash:", sha1Dec)
return sha1Bin, utils.BoolBinEncode(sha1Bin)
}
func (t *Transmission) dataLengthBin() (string, []bool) {
dataLength := 0
for _, packet := range t.data {
dataLength += len(*packet.data)
}
t.dataLength = dataLength
headerDataLengthInteger := int64(dataLength)
headerDataLengthBin := strconv.FormatInt(headerDataLengthInteger, 2)
headerDataLengthBin = utils.LeftPad(headerDataLengthBin, options.HeaderDataLengthIntegerBitLength)
headerDataLengthDec := strconv.FormatInt(headerDataLengthInteger, 10)
fmt.Println("Data Length:", headerDataLengthDec)
return headerDataLengthBin, utils.BoolBinEncode(headerDataLengthBin)
}
func (t *Transmission) allData() *[]bool {
data := t.header.packetData()
for _, packet := range t.data {
data = append(data, packet.packetData()...)
}
carrierSpacing := float64(t.options.OMFSKConstant) / (float64(t.options.FrameDuration) / 1000.0)
carrierCount := int(math.Floor(float64(t.options.Bandwidth) / carrierSpacing))
fullLength := int(math.Ceil(float64(len(data))/float64(carrierCount))) * carrierCount
paddingAmount := fullLength - len(data)
for i := 0; i < paddingAmount; i++ {
data = append(data, false)
}
data = interleave(data)
return &data
}
func (t *Transmission) modulate() {
if t.modulator == nil {
t.modulator = &modulation.Modulator{}
t.modulator.Options = t.options
allData := t.allData()
t.modulator.SetData(allData)
}
t.modulator.Reset()
duration := float64(t.modulator.FrameCount()*t.options.FrameDuration) / 1000
fmt.Println(t.originalDataLength, "bits to transfer")
fmt.Println(duration, "second transfer time")
fmt.Println(int64(float64(t.dataLength)/duration), "bps real")
fmt.Println(int64(float64(t.originalDataLength)/duration), "bps effective")
}
func (t *Transmission) BuildWav(filename string) {
t.modulate()
t.modulator.BuildWav(filename)
}
func (t *Transmission) Wave() []float64 {
t.modulate()
return t.modulator.FullWave()
}