pce.go

package minigo

import "time"

const MaxSubPerMinute = 20
const NackTimer = 1140 * time.Millisecond

// Imported from 'linux/lib/crc7.c'
//
// Table for CRC-7 (polynomial x^7 + x^3 + 1).
// This is a big-endian CRC (msbit is highest power of x),
// aligned so the msbit of the byte is the x^6 coefficient
// and the lsbit is not used.
var crc7SyndromeTable = []byte{
	0x00, 0x12, 0x24, 0x36, 0x48, 0x5a, 0x6c, 0x7e,
	0x90, 0x82, 0xb4, 0xa6, 0xd8, 0xca, 0xfc, 0xee,
	0x32, 0x20, 0x16, 0x04, 0x7a, 0x68, 0x5e, 0x4c,
	0xa2, 0xb0, 0x86, 0x94, 0xea, 0xf8, 0xce, 0xdc,
	0x64, 0x76, 0x40, 0x52, 0x2c, 0x3e, 0x08, 0x1a,
	0xf4, 0xe6, 0xd0, 0xc2, 0xbc, 0xae, 0x98, 0x8a,
	0x56, 0x44, 0x72, 0x60, 0x1e, 0x0c, 0x3a, 0x28,
	0xc6, 0xd4, 0xe2, 0xf0, 0x8e, 0x9c, 0xaa, 0xb8,
	0xc8, 0xda, 0xec, 0xfe, 0x80, 0x92, 0xa4, 0xb6,
	0x58, 0x4a, 0x7c, 0x6e, 0x10, 0x02, 0x34, 0x26,
	0xfa, 0xe8, 0xde, 0xcc, 0xb2, 0xa0, 0x96, 0x84,
	0x6a, 0x78, 0x4e, 0x5c, 0x22, 0x30, 0x06, 0x14,
	0xac, 0xbe, 0x88, 0x9a, 0xe4, 0xf6, 0xc0, 0xd2,
	0x3c, 0x2e, 0x18, 0x0a, 0x74, 0x66, 0x50, 0x42,
	0x9e, 0x8c, 0xba, 0xa8, 0xd6, 0xc4, 0xf2, 0xe0,
	0x0e, 0x1c, 0x2a, 0x38, 0x46, 0x54, 0x62, 0x70,
	0x82, 0x90, 0xa6, 0xb4, 0xca, 0xd8, 0xee, 0xfc,
	0x12, 0x00, 0x36, 0x24, 0x5a, 0x48, 0x7e, 0x6c,
	0xb0, 0xa2, 0x94, 0x86, 0xf8, 0xea, 0xdc, 0xce,
	0x20, 0x32, 0x04, 0x16, 0x68, 0x7a, 0x4c, 0x5e,
	0xe6, 0xf4, 0xc2, 0xd0, 0xae, 0xbc, 0x8a, 0x98,
	0x76, 0x64, 0x52, 0x40, 0x3e, 0x2c, 0x1a, 0x08,
	0xd4, 0xc6, 0xf0, 0xe2, 0x9c, 0x8e, 0xb8, 0xaa,
	0x44, 0x56, 0x60, 0x72, 0x0c, 0x1e, 0x28, 0x3a,
	0x4a, 0x58, 0x6e, 0x7c, 0x02, 0x10, 0x26, 0x34,
	0xda, 0xc8, 0xfe, 0xec, 0x92, 0x80, 0xb6, 0xa4,
	0x78, 0x6a, 0x5c, 0x4e, 0x30, 0x22, 0x14, 0x06,
	0xe8, 0xfa, 0xcc, 0xde, 0xa0, 0xb2, 0x84, 0x96,
	0x2e, 0x3c, 0x0a, 0x18, 0x66, 0x74, 0x42, 0x50,
	0xbe, 0xac, 0x9a, 0x88, 0xf6, 0xe4, 0xd2, 0xc0,
	0x1c, 0x0e, 0x38, 0x2a, 0x54, 0x46, 0x70, 0x62,
	0x8c, 0x9e, 0xa8, 0xba, 0xc4, 0xd6, 0xe0, 0xf2,
}

func crc7BeByte(crc, data byte) byte {
	return crc7SyndromeTable[crc^data]
}

func getCRC7(data []byte) byte {
	var crc byte
	for _, b := range data {
		crc = crc7BeByte(crc, b)
	}

	return crc >> 1
}

func GetPCEBlock(buf []byte) []byte {
	// make sure we a have the good length
	inner := make([]byte, 15)
	copy(inner, buf)

	crc := getCRC7(inner)

	inner = append(inner, SetParity(crc), 0)
	return inner
}

func GetSynFrame(blockId byte, block []byte) []byte {
	buf := ApplyParity([]byte{Syn, Syn, blockId + 0x40})
	return append(buf, block...)
}

func ApplyPCE(in []byte) (out [][]byte) {
	tmp := ApplyParity(in)

	for pos := 0; pos < len(tmp); pos += 15 {
		out = append(out, GetPCEBlock(tmp[pos:]))
	}

	return out
}

func GetRequestPCE() []byte {
	buf, _ := ProCode(Pro2)
	buf = append(buf, Start, PCE)

	return ApplyParity(buf)
}

func AckPCE(data []byte) (ack bool, next bool) {
	if data[0] == Esc {
		if len(data) == 1 {
			return false, true
		}

		if data[1] == Pro2 {
			if len(data) == 2 {
				return false, true
			}

			if data[2] == Fonctionnement {
				if len(data) == 3 {
					return false, true
				}

				return BitReadAt(data[3], 2), false
			}
		}
	}

	return
}