refactored int codecs to DRY and easy support signed/unsigned values

README.md

@@ -8,4 +8,10 @@ Goals:
 - Pack/unpack byte tools
 - 2 flavors of space-effecient varint packing
 - CRCs and CRC-protected blocks
-- Async variants
+- Async variants
+
+# Some publics
+
+## SmartInt codec
+
+Variable-length signed and unsigned integer codec, see `object SmartInt`. For not too small numbers it is slightly more effective than `VarInt` codec, for example on `Long` values it saves a byte.

src/commonMain/kotlin/net.sergeych.bintools/DataSink.kt

@@ -1,8 +1,8 @@
 package net.sergeych.bintools
 
-abstract class DataSink {
+interface DataSink {
 
-    abstract fun writeByte(data: Byte)
+    fun writeByte(data: Byte)
 
     fun writeByte(data: Int) = writeByte(data.toByte())
 
@@ -16,7 +16,7 @@ abstract class DataSink {
     }
 }
 
-class ArrayDataSink : DataSink() {
+class ArrayDataSink : DataSink {
     private val result = mutableListOf<Byte>()
 
     override fun writeByte(data: Byte) {

src/commonMain/kotlin/net.sergeych.bintools/DataSource.kt

@@ -6,16 +6,16 @@ package net.sergeych.bintools
  * like multiplatform version of DataInput
  *
  */
-abstract class DataSource {
+interface DataSource {
 
-    abstract fun readByte(): Byte
+    fun readByte(): Byte
 
-    abstract val position: Int
+    val position: Int
 
-    open fun readUByte() = readByte().toUByte()
+    fun readUByte() = readByte().toUByte()
 
     @Suppress("unused")
-    open fun readBytes(size: Int): ByteArray =
+    fun readBytes(size: Int): ByteArray =
         ByteArray(size).also { a ->
             for( i in 0..size)
                 a[i] = readByte()
@@ -23,7 +23,7 @@ abstract class DataSource {
 }
 
 fun ByteArray.toDataSource(): DataSource =
-    object : DataSource() {
+    object : DataSource {
         override var position = 0
 
         override fun readByte(): Byte = this@toDataSource[position++]

src/commonMain/kotlin/net.sergeych.bintools/IntCodec.kt

@@ -0,0 +1,87 @@
+package net.sergeych.bintools
+
+import com.icodici.ubdata.Varint
+import kotlin.reflect.typeOf
+
+/**
+ * The common interface to whatever variable (or even fixed) length integer encoder.
+ * Implementation can just override [encodeUnsigned] and [decodeUnsigned] pair and
+ * get the rest (incliding signed codec) out of the box. DRY for [Smartint] and [Varint]
+ * codecs.
+ */
+interface IntCodec {
+    fun encodeUnsigned(value: ULong,sink: DataSink)
+
+    fun decodeUnsigned(source: DataSource): ULong
+
+    /**
+     * Default signed codec uses bit 0 as a sign (to keep packed as small as possible)
+     */
+    fun encodeSigned(value: Long, sink: DataSink): Unit {
+        var sigBit: ULong
+        var x: ULong
+        if (value < 0) {
+            x = (-value).toULong()
+            sigBit = 1u
+        } else {
+            x = value.toULong()
+            sigBit = 0u
+        }
+        encodeUnsigned((x shl 1) or sigBit, sink)
+    }
+
+    /**
+     * Default signed codec uses bit 0 as a sign (to keep packed as small as possible)
+     */
+    fun decodeSigned(source: DataSource): Long {
+        val x = decodeUnsigned(source)
+        val result = (x shr 1).toLong()
+        return if ((x and 1u).toInt() != 0) -result else result
+    }
+
+    fun encodeUnsigned(value: ULong): ByteArray {
+        return ArrayDataSink().also { encodeUnsigned(value, it) }.toByteArray()
+    }
+
+    fun decodeUnsigned(packed: ByteArray) = decodeUnsigned(packed.toDataSource())
+
+    fun encodeSigned(value: Long): ByteArray {
+        return ArrayDataSink().also { encodeSigned(value, it) }.toByteArray()
+    }
+
+    fun decodeSigned(data: ByteArray): Long {
+        return decodeSigned(data.toDataSource())
+    }
+}
+
+inline fun <reified T : Any> IntCodec.decode(source: ByteArray): T {
+    return decode(source.toDataSource())
+}
+
+inline fun <reified T : Any> IntCodec.decode(source: DataSource): T {
+    return when (typeOf<T>()) {
+        typeOf<UByte>() -> decodeUnsigned(source).toUByte()
+        typeOf<UInt>() -> decodeUnsigned(source).toUInt()
+        typeOf<ULong>() -> decodeUnsigned(source).toULong()
+        typeOf<Byte>() -> decodeSigned(source).toByte()
+        typeOf<Int>() -> decodeSigned(source).toInt()
+        typeOf<Long>() -> decodeSigned(source).toLong()
+        else ->
+            throw IllegalArgumentException("can't decode to ${T::class.simpleName}")
+    } as T
+}
+
+inline fun <reified T : Any> IntCodec.encode(x: T, dout: DataSink) {
+    when (x) {
+        is UByte -> encodeUnsigned(x.toULong(), dout)
+        is UInt -> encodeUnsigned(x.toULong(), dout)
+        is ULong -> encodeUnsigned(x, dout)
+        is Byte -> encodeSigned(x.toLong(), dout)
+        is Int -> encodeSigned(x.toLong(), dout)
+        is Long -> encodeSigned(x, dout)
+        else -> throw IllegalArgumentException("can't encode with varitn ${x::class.simpleName}: $x")
+    }
+}
+
+inline fun <reified T : Any> IntCodec.encode(x: T): ByteArray =
+    ArrayDataSink().also { encode(x, it) }.toByteArray()

src/commonMain/kotlin/net.sergeych.bintools/simple_codecs.kt

@@ -29,11 +29,12 @@ private val hexDigits = "0123456789ABCDEF"
 fun Long.encodeToHex(length: Int = 0): String {
     var result = ""
     var value = this
-    if (value < 0) throw IllegalArgumentException("cant convert to hex negative (ambiguous)")
+    var end = if( value >= 0 ) 0L else -1L
+//    if (value < 0) throw IllegalArgumentException("cant convert to hex negative (ambiguous)")
     do {
         result = hexDigits[(value and 0x0f).toInt()] + result
         value = value shr 4
-    } while (value > 0)
+    } while (value != end)
     while (result.length < length) result = "0" + result
     return result
 }

src/commonMain/kotlin/net.sergeych.bintools/smartint.kt

@@ -2,13 +2,12 @@
 
 package com.icodici.ubdata
 
-import net.sergeych.bintools.ArrayDataSink
+import net.sergeych.bintools.*
-import net.sergeych.bintools.DataSink
-import net.sergeych.bintools.DataSource
-import net.sergeych.bintools.toDataSource
 
 /**
- * Smart variable-length long encoding tools, async.
+ * Smart variable-length long encoding tools, async. It gives byte-size gain from 64 bits numbers
+ * so it is very useful when encoding big numbers or at least very bui long values. In other cases
+ * [Varint] works faster, and extra bits it uses does not play
  *
  * | Bytes sz | varint bits | smartint bits |
  * |:-----:|:------:|:---------:|
@@ -49,13 +48,13 @@ import net.sergeych.bintools.toDataSource
  *  sequence.
  *
  */
-object Smartint {
+object Smartint : IntCodec {
 
     private val v0limit: ULong = (1L shl 6).toULong()
     private val v1limit = (1L shl 14).toULong()
     private val v2limit = (1L shl 22).toULong()
 
-    fun encode(value: ULong, sink: DataSink) {
+    override fun encodeUnsigned(value: ULong, sink: DataSink) {
         when {
             value < v0limit -> encodeSeq(sink, 0, value)
 
@@ -82,7 +81,7 @@ object Smartint {
                     (value shr 6) and 0xFFu,
                     (value shr 14) and 0xFFu,
                 )
-                Varint.encode(value shr 22, sink)
+                Varint.encodeUnsigned(value shr 22, sink)
             }
         }
     }
@@ -98,7 +97,7 @@ object Smartint {
         }
     }
 
-    fun decode(source: DataSource): ULong {
+    override fun decodeUnsigned(source: DataSource): ULong {
         fun get(): ULong = source.readUByte().toULong()
         val first = get().toUInt()
         var type = (first and 3u).toInt()
@@ -112,39 +111,7 @@ object Smartint {
         result = result or (get() shl 14)
         if (type == 0) return result  // type 2
 
-        return result or (Varint.decode(source) shl 22)
+        return result or (Varint.decodeUnsigned(source) shl 22)
     }
 
-    fun encodeSigned(value: Long, sink: DataSink) {
-        val sigBit: ULong
-        val x: ULong
-        if (value < 0) {
-            x = (-value).toULong()
-            sigBit = 1u
-        } else {
-            x = value.toULong()
-            sigBit = 0u
-        }
-        Varint.encode((x shl 1) or sigBit, sink)
-    }
-
-    fun decodeSigned(source: DataSource): Long {
-        val x = Varint.decode(source)
-        val result = (x shr 1).toLong()
-        return if ((x and 1u).toInt() != 0) -result else result
-    }
-
-    fun encode(value: ULong): ByteArray {
-        return ArrayDataSink().also { encode(value, it) }.toByteArray()
-    }
-
-    fun decode(packed: ByteArray) = decode(packed.toDataSource())
-
-    fun encodeSigned(value: Long): ByteArray {
-        return ArrayDataSink().also { encodeSigned(value, it) }.toByteArray()
-    }
-
-    fun decodeSigned(data: ByteArray): Long {
-        return decodeSigned(data.toDataSource())
-    }
 }

src/commonMain/kotlin/net.sergeych.bintools/varint.kt

@@ -2,10 +2,7 @@
 
 package com.icodici.ubdata
 
-import net.sergeych.bintools.ArrayDataSink
+import net.sergeych.bintools.*
-import net.sergeych.bintools.DataSink
-import net.sergeych.bintools.DataSource
-import net.sergeych.bintools.toDataSource
 
 /**
  * Variable-length long integer encoding. the MSB (0x80) bit of each byte flags
@@ -16,21 +13,8 @@ import net.sergeych.bintools.toDataSource
  * encoding numbers that needs more than 22 bits. With smaller numbers its either
  * same or even worse, see [Smartint] docs.
  */
-object Varint {
+object Varint: IntCodec {
-    fun encodeSigned(value: Long, sink: DataSink): Unit {
+    override fun encodeUnsigned(value: ULong, dout: DataSink) {
-        var sigBit: ULong
-        var x: ULong
-        if (value < 0) {
-            x = (-value).toULong()
-            sigBit = 1u
-        } else {
-            x = value.toULong()
-            sigBit = 0u
-        }
-        encode((x shl 1) or sigBit, sink)
-    }
-
-    fun encode(value: ULong, dout: DataSink) {
         var rest = value
         do {
             val x = (rest and 127u).toInt()
@@ -43,7 +27,7 @@ object Varint {
         } while (rest > 0u)
     }
 
-    fun decode(source: DataSource): ULong {
+    override fun decodeUnsigned(source: DataSource): ULong {
         var result: ULong = 0u
         var count = 0
         while (true) {
@@ -55,28 +39,4 @@ object Varint {
         }
         return result
     }
-
-
-    fun decodeSigned(source: DataSource): Long {
-        val x = decode(source)
-        val result = (x shr 1).toLong()
-        return if ((x and 1u).toInt() != 0) -result else result
-    }
-
-    fun encode(value: ULong): ByteArray {
-        return ArrayDataSink().also { encode(value, it) }.toByteArray()
-    }
-
-    fun decode(packed: ByteArray) = decode(packed.toDataSource())
-
-    fun encodeSigned(value: Long): ByteArray {
-        return ArrayDataSink().also { encodeSigned(value, it) }.toByteArray()
-    }
-
-    fun decodeSigned(data: ByteArray): Long {
-        return decodeSigned(data.toDataSource())
-    }
-
-
-
 }

src/commonTest/kotlin/bintools/SmartintTest.kt

@@ -1,16 +1,18 @@
 package bintools
 
 import com.icodici.ubdata.Smartint
+import com.icodici.ubdata.Varint
+import net.sergeych.bintools.decode
+import net.sergeych.bintools.encode
 import net.sergeych.bintools.encodeToHex
 import kotlin.test.Test
 import kotlin.test.assertEquals
 
 class SmartintTest {
 
-    fun testValue(x: Long) {
+    inline fun <reified T:Number>testValue(x: T) {
-        assertEquals(x.toULong(), Smartint.decode(Smartint.encode(x.toULong())))
+        assertEquals(x, Smartint.decode(Smartint.encode(x)))
-        assertEquals(x, Smartint.decodeSigned(Smartint.encodeSigned(x)))
+        println("+ ${x}: ${Smartint.encode(x).encodeToHex()}")
-        println("+ ${x}: ${Smartint.encode(x.toULong()).encodeToHex()}")
     }
 
     fun testAround(bits: Int) {
@@ -19,10 +21,12 @@ class SmartintTest {
         var median: Long = (1.toULong() shl bits).toLong()
         for( x in (median-2)..(median+2)) {
             testValue(x)
+            testValue(-x)
         }
         median = median * 3 / 2
         for( x in (median-5)..(median+5)) {
             testValue(x)
+            testValue(-x)
         }
     }
 
@@ -39,6 +43,13 @@ class SmartintTest {
     }
 
     @Test
-    fun decode() {
+    fun compareTest() {
+        for( x in listOf<ULong>(0uL, 1uL, 66uL, 129uL, 219uL, 0x1122uL, 0xFFEEuL, 0xAAbbCCdduL,
+            0x1111222233334444uL, (1UL shl 63))) {
+            //                     1--12--23--34--4
+            println("--- $x / 0x${x.encodeToHex(8)}")
+            println("V: ${Varint.encode(x).encodeToHex()}")
+            println("S: ${Smartint.encode(x).encodeToHex()}")
+        }
     }
 }

src/commonTest/kotlin/bintools/VarintTest.kt

@@ -1,16 +1,18 @@
 package bintools
 
 import com.icodici.ubdata.Varint
+import net.sergeych.bintools.decode
+import net.sergeych.bintools.encode
 import net.sergeych.bintools.encodeToHex
 import kotlin.test.Test
 import kotlin.test.assertEquals
 
 class VarintTest {
 
-    fun testValue(x: Long) {
+    inline fun <reified T: Any>testValue(x: T) {
-        assertEquals(x.toULong(), Varint.decode(Varint.encode(x.toULong())))
+        assertEquals(x, Varint.decode(Varint.encode(x)))
-        assertEquals(x, Varint.decodeSigned(Varint.encodeSigned(x)))
+//        assertEquals(x, Varint.decodeSigned(Varint.encodeSigned(x)))
-        println("+ ${x}: ${Varint.encode(x.toULong()).encodeToHex()}")
+        println("+ ${x}: ${Varint.encode(x).encodeToHex()}")
     }
 
     fun testAround(bits: Int) {
@@ -18,16 +20,19 @@ class VarintTest {
         var median: Long = (1.toULong() shl bits).toLong()
         for( x in (median-5)..(median+5)) {
             testValue(x)
+            testValue(-x)
         }
         median = median * 3 / 2
         for( x in (median-5)..(median+5)) {
             testValue(x)
+            testValue(-x)
         }
     }
 
     @Test
     fun encode() {
 //        for( i in 0..300) testValue(i.toLong())
+        testAround(7)
         testAround(7)
         testAround(14)
         testAround(21)
@@ -35,6 +40,9 @@ class VarintTest {
     }
 
     @Test
-    fun decode() {
+    fun negative() {
+        testValue(-1)
+        testValue(-2)
+        testValue(-3)
     }
 }