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Contrail reworked and finished

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This commit is contained in:
Sergey Chernov 2024-06-19 05:40:13 +07:00
parent f64412fdc7
commit e4e3b5ba8b
3 changed files with 39 additions and 16 deletions
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30
src/commonMain/kotlin/net/sergeych/crypto2/Contrail.kt Normal file
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package net.sergeych.crypto2
import net.sergeych.bintools.CRC
/**
* The crc8-protected binary data manipulation. It uses crc8-bluetooth polynomial (0xA7)
* flavor. Note that crc8 provides good protection only for relatively small data sets.
*/
object Contrail {
/**
* Create a contrail by adding a crc byte to the end of [data]. The Result is always one byte longer.
*/
fun create(data: UByteArray): UByteArray = data + CRC.crc8(data.toByteArray())
/**
* Check the contrail is valid.
*/
fun isValid(data: UByteArray): Boolean = CRC.crc8(
data.copyOfRange(0, data.size - 1).toByteArray()
) == data.last()
/**
* Check that the contrail is valid and extracts its data
* @return the data without crc or null if it is not valid
*/
fun unpack(contrailData: UByteArray): UByteArray? =
if (isValid(contrailData)) contrailData.sliceArray(0..<contrailData.size - 1) else null
}

9
src/commonMain/kotlin/net/sergeych/crypto2/contrail.kt
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package net.sergeych.crypto2
import net.sergeych.bintools.CRC
fun isValidContrail(data: UByteArray): Boolean = CRC.crc8(
data.copyOfRange(1, data.size).toByteArray()
) == data[0]
fun createContrail(data: UByteArray): UByteArray = ubyteArrayOf(CRC.crc8(data.toByteArray())) + data

16
src/commonTest/kotlin/ToolsTest.kt
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@ -1,19 +1,21 @@
import kotlinx.coroutines.test.runTest
import net.sergeych.crypto2.Contrail
import net.sergeych.crypto2.NumericNonce
import net.sergeych.crypto2.createContrail
import net.sergeych.crypto2.initCrypto
import net.sergeych.crypto2.isValidContrail
import kotlin.test.*
class ToolsTest {
@Test
fun testContrails() = runTest {
initCrypto()
val c = createContrail(ubyteArrayOf(1u, 2u, 3u, 4u, 5u))
assertEquals(134u, c[0])
assertTrue { isValidContrail(c) }
c[2] = 11u
assertFalse { isValidContrail(c) }
val data = ubyteArrayOf(1u, 2u, 3u, 4u, 5u)
val c = Contrail.create(data)
assertTrue { Contrail.isValid(c) }
c[2] = c[2] xor 11u
assertFalse { Contrail.isValid(c) }
c[2] = c[2] xor 11u
assertTrue { Contrail.isValid(c) }
assertContentEquals(data,Contrail.unpack(c))
}
@Test