some support for fixed number

src/commonTest/kotlin/bipack/BipackEncoderTest.kt

@@ -2,6 +2,7 @@ package bipack
 
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import net.sergeych.bintools.encodeToHex
 import net.sergeych.bintools.toDump
 import net.sergeych.bipack.*
 import kotlin.experimental.xor
@@ -297,4 +298,28 @@ class BipackEncoderTest {
         assertEquals(x, d.decodeFromBipack())
     }
 
+    @Serializable
+    data class FI32(@Fixed val i: Int)
+
+    @Serializable
+    data class FU32(@Fixed val i: UInt)
+
+    @Serializable
+    data class FI16(@Fixed val i: Short)
+
+    @Serializable
+    data class FU16(@Fixed val i: UShort)
+
+    @Test
+    fun testFixedInt() {
+        val a= FI32(127)
+        println(BipackEncoder.encode(a).toDump())
+        assertContentEquals(byteArrayOf(0,0,0,0x7f), BipackEncoder.encode(a))
+        assertEquals("FF FF FF FF", BipackEncoder.encode(FI32(-1)).encodeToHex())
+        assertEquals(-1, BipackEncoder.encode(FI32(-1)).decodeFromBipack<FI32>().i)
+        assertEquals("FF FF FF FF", BipackEncoder.encode(FU32(0xFFFFFFFFu)).encodeToHex())
+        assertEquals("FF 01 02 03", BipackEncoder.encode(FU32(0xFF010203u)).encodeToHex())
+        assertEquals("FF 03", BipackEncoder.encode(FU16(0xFF03u)).encodeToHex())
+        assertEquals(0x7ffeu, BipackEncoder.encode(FU16(0x7ffeu)).decodeFromBipack<FU16>().i)
+    }
 }