some support for fixed number

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

@@ -36,6 +36,10 @@ inline fun <reified T:Any>DataSink.writeNumber(value: T) {
 fun DataSink.writeI32(value: Int) {
     writeBytes(intToBytes(value))
 }
+
+fun DataSink.writeI16(value: Short) {
+    writeBytes(shortToBytes(value))
+}
 fun DataSink.writeU32(value: UInt) {
     writeBytes(uintToBytes(value))
 }

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

@@ -28,6 +28,7 @@ interface DataSource {
 
     fun readU32(): UInt = bytesToUInt(readBytes(4))
     fun readI32(): Int = bytesToInt(readBytes(4))
+    fun readI16(): Short = bytesToShort(readBytes(2))
     fun readI64(): Long = bytesToLong(readBytes(8))
 
     fun readDouble() = Double.fromBits(readI64())

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

@@ -20,6 +20,15 @@ fun intToBytes(value: Int): ByteArray {
     }
     return result
 }
+fun shortToBytes(value: Short): ByteArray {
+    var l = value.toInt()
+    val result = ByteArray(2)
+    for (i in 1 downTo 0) {
+        result[i] = (l and 0xFF).toByte()
+        l = l shr 8
+    }
+    return result
+}
 
 fun uintToBytes(value: UInt): ByteArray {
     var l = value
@@ -52,6 +61,15 @@ fun bytesToInt(b: ByteArray): Int {
     return result
 }
 
+fun bytesToShort(b: ByteArray): Short {
+    var result: Int = 0
+    for (i in 0 until 2) {
+        result = result shl 8
+        result = result or (b[i].toInt() and 0xFF)
+    }
+    return result.toShort()
+}
+
 fun bytesToUInt(b: ByteArray): UInt {
     var result = 0u
     for (i in 0 until 4) {

src/commonMain/kotlin/net.sergeych.bipack/BipackDecoder.kt

@@ -15,18 +15,26 @@ import net.sergeych.bintools.*
  * Decode BiPack format. Note that it relies on [DataSource] so can throw [DataSource.EndOfData]
  * excpetion. Specific frames when used can throw [InvalidFrameException] and its derivatives.e
  */
-class BipackDecoder(val input: DataSource, var elementsCount: Int = 0,val isCollection: Boolean = false,
-    val  hasFixedSize: Boolean = false) : AbstractDecoder() {
+class BipackDecoder(
+    val input: DataSource, var elementsCount: Int = 0, val isCollection: Boolean = false,
+    val hasFixedSize: Boolean = false,
+) : AbstractDecoder() {
     private var elementIndex = 0
 
     private var nextIsUnsigned = false
     private var fixedSize = -1
+    private var fixedNumber = false
 
     override val serializersModule: SerializersModule = EmptySerializersModule
     override fun decodeBoolean(): Boolean = input.readByte().toInt() != 0
     override fun decodeByte(): Byte = input.readByte()
-    override fun decodeShort(): Short = if (nextIsUnsigned) input.readNumber<UInt>().toShort() else input.readNumber()
-    override fun decodeInt(): Int = if (nextIsUnsigned) input.readNumber<UInt>().toInt() else input.readNumber()
+    override fun decodeShort(): Short =
+        if( fixedNumber ) input.readI16()
+        else if (nextIsUnsigned) input.readNumber<UInt>().toShort() else input.readNumber()
+    override fun decodeInt(): Int =
+        if (fixedNumber) input.readI32()
+        else if (nextIsUnsigned) input.readNumber<UInt>().toInt() else input.readNumber()
+
     override fun decodeLong(): Long = if (nextIsUnsigned) input.readNumber<ULong>().toLong() else input.readNumber()
     override fun decodeFloat(): Float = input.readFloat()
     override fun decodeDouble(): Double = input.readDouble()
@@ -44,10 +52,11 @@ class BipackDecoder(val input: DataSource, var elementsCount: Int = 0,val isColl
     override fun decodeElementIndex(descriptor: SerialDescriptor): Int {
         if (elementIndex >= elementsCount) return CompositeDecoder.DECODE_DONE
         nextIsUnsigned = false
-        for( a in descriptor.getElementAnnotations(elementIndex)) {
-            when(a) {
+        for (a in descriptor.getElementAnnotations(elementIndex)) {
+            when (a) {
                 is Unsigned -> nextIsUnsigned = true
                 is FixedSize -> fixedSize = a.size
+                is Fixed -> fixedNumber = true
             }
         }
         return elementIndex++
@@ -65,7 +74,7 @@ class BipackDecoder(val input: DataSource, var elementsCount: Int = 0,val isColl
 
         // Note: we should read from 'source' explicitely as it might ve
         // CRC-calculating one, and the fields below are CRC protected too:
-        var count = if( fixedSize >= 0 ) fixedSize else descriptor.elementsCount
+        var count = if (fixedSize >= 0) fixedSize else descriptor.elementsCount
         for (a in descriptor.annotations) {
             if (a is Extendable)
                 count = source.readVarUInt().toInt()
@@ -83,7 +92,7 @@ class BipackDecoder(val input: DataSource, var elementsCount: Int = 0,val isColl
     }
 
     override fun decodeCollectionSize(descriptor: SerialDescriptor): Int {
-        return if( hasFixedSize )
+        return if (hasFixedSize)
             elementsCount
         else
             input.readNumber<UInt>().toInt()

src/commonMain/kotlin/net.sergeych.bipack/BipackEncoder.kt

@@ -13,6 +13,7 @@ class BipackEncoder(val output: DataSink) : AbstractEncoder() {
 
     private var nextIsUnsigned = false
     private var fixedSize: Int = -1
+    private var fixedNumber: Boolean = false
 
     override fun encodeElement(descriptor: SerialDescriptor, index: Int): Boolean =
         super.encodeElement(descriptor, index).also {
@@ -21,21 +22,25 @@ class BipackEncoder(val output: DataSink) : AbstractEncoder() {
                 when (a) {
                     is Unsigned -> nextIsUnsigned = true
                     is FixedSize -> fixedSize = a.size
+                    is Fixed -> fixedNumber = true
                 }
             }
-//            nextIsUnsigned = descriptor.getElementAnnotations(index).any { it is Unsigned }
         }
 
     override val serializersModule: SerializersModule = EmptySerializersModule
     override fun encodeBoolean(value: Boolean) = output.writeByte(if (value) 1 else 0)
     override fun encodeByte(value: Byte) = output.writeByte(value.toInt())
-    override fun encodeShort(value: Short) = if (nextIsUnsigned)
-        output.writeNumber(value.toUInt())
-    else
-        output.writeNumber(value.toInt())
+    override fun encodeShort(value: Short) =
+        if (fixedNumber) output.writeI16(value)
+        else if (nextIsUnsigned)
+            output.writeNumber(value.toUInt())
+        else
+            output.writeNumber(value.toInt())
 
     override fun encodeInt(value: Int) =
-        if (nextIsUnsigned) output.writeNumber(value.toUInt())
+        if (fixedNumber)
+            output.writeI32(value)
+        else if (nextIsUnsigned) output.writeNumber(value.toUInt())
         else output.writeNumber(value)
 
     fun encodeUInt(value: UInt) = output.writeNumber(value)

src/commonMain/kotlin/net.sergeych.bipack/annotations.kt

@@ -58,6 +58,10 @@ annotation class Unsigned
 @Target(AnnotationTarget.FIELD, AnnotationTarget.PROPERTY)
 annotation class FixedSize(val size: Int)
 
+@SerialInfo
+@Target(AnnotationTarget.FIELD, AnnotationTarget.PROPERTY)
+annotation class Fixed
+
 open class InvalidFrameException(reason: String) : Exception(reason)
 class InvalidFrameHeaderException(reason: String = "Frame header does not match") : InvalidFrameException(reason)
 class InvalidFrameCRCException : InvalidFrameException("Checksum CRC32 failed")