[6.0.0] Conversion from Long-encoded nBits representation to BigInt and back

core/shared/src/main/scala/sigma/SigmaDsl.scala

@@ -727,6 +727,20 @@ trait SigmaDslBuilder {
     */
   def groupGenerator: GroupElement
 
+  /**
+    * @return big integer provided as input approximately encoded using NBits,
+    *         see (https://bitcoin.stackexchange.com/questions/57184/what-does-the-nbits-value-represent)
+    *         for format details
+    */
+  def encodeNbits(bi: BigInt): Long
+
+  /**
+    * @return big integer decoded from NBits value provided,
+    *         see (https://bitcoin.stackexchange.com/questions/57184/what-does-the-nbits-value-represent)
+    *         for format details
+    */
+  def decodeNbits(l: Long): BigInt
+
   /**
     * Transforms serialized bytes of ErgoTree with segregated constants by replacing constants
     * at given positions with new values. This operation allow to use serialized scripts as

core/shared/src/main/scala/sigma/reflection/ReflectionData.scala

@@ -468,6 +468,12 @@ object ReflectionData {
         },
         mkMethod(clazz, "fromBigEndianBytes", Array[Class[_]](cColl, classOf[RType[_]])) { (obj, args) =>
           obj.asInstanceOf[SigmaDslBuilder].fromBigEndianBytes(args(0).asInstanceOf[Coll[Byte]])(args(1).asInstanceOf[RType[_]])
+        },
+        mkMethod(clazz, "encodeNbits", Array[Class[_]](classOf[BigInt])) { (obj, args) =>
+          obj.asInstanceOf[SigmaDslBuilder].encodeNbits(args(0).asInstanceOf[BigInt])
+        },
+        mkMethod(clazz, "decodeNbits", Array[Class[_]](classOf[Long])) { (obj, args) =>
+          obj.asInstanceOf[SigmaDslBuilder].decodeNbits(args(0).asInstanceOf[Long])
         }
       )
     )

data/shared/src/main/scala/sigma/SigmaDataReflection.scala

@@ -86,6 +86,14 @@ object SigmaDataReflection {
     )
   )
 
+  registerClassEntry(classOf[ByteArrayToLong],
+    constructors = Array(
+      mkConstructor(Array(classOf[Value[_]])) { args =>
+        new ByteArrayToLong(args(0).asInstanceOf[Value[SByteArray]])
+      }
+    )
+  )
+
   registerClassEntry(classOf[LongToByteArray],
     constructors = Array(
       mkConstructor(Array(classOf[Value[_]])) { args =>

data/shared/src/main/scala/sigma/ast/methods.scala

@@ -4,18 +4,21 @@ import org.ergoplatform._
 import org.ergoplatform.validation._
 import sigma.Evaluation.stypeToRType
 import sigma._
+import sigma.{VersionContext, _}
 import sigma.ast.SCollection.{SBooleanArray, SBoxArray, SByteArray, SByteArray2, SHeaderArray}
+import sigma.ast.SGlobalMethods.{decodeNBitsMethod, encodeNBitsMethod}
 import sigma.ast.SMethod.{MethodCallIrBuilder, MethodCostFunc, javaMethodOf}
 import sigma.ast.SType.{TypeCode, paramT, tT}
 import sigma.ast.syntax.{SValue, ValueOps}
 import sigma.data.ExactIntegral.{ByteIsExactIntegral, IntIsExactIntegral, LongIsExactIntegral, ShortIsExactIntegral}
 import sigma.data.NumericOps.BigIntIsExactIntegral
 import sigma.data.OverloadHack.Overloaded1
-import sigma.data.{DataValueComparer, KeyValueColl, Nullable, RType, SigmaConstants}
+import sigma.data.{CBigInt, DataValueComparer, KeyValueColl, Nullable, RType, SigmaConstants}
 import sigma.eval.{CostDetails, ErgoTreeEvaluator, TracedCost}
 import sigma.reflection.RClass
 import sigma.serialization.CoreByteWriter.ArgInfo
 import sigma.serialization.{DataSerializer, SigmaByteWriter, SigmaSerializer}
+import sigma.util.NBitsUtils
 import sigma.utils.SparseArrayContainer
 
 import scala.annotation.unused
@@ -1806,6 +1809,18 @@ case object SGlobalMethods extends MonoTypeMethods {
       "Decode a number from big endian bytes.",
       ArgInfo("first", "Bytes which are big-endian encoded number."))
 
+  private lazy val EnDecodeNBitsCost = FixedCost(JitCost(5)) // the same cost for nbits encoding and decoding
+
+  lazy val encodeNBitsMethod: SMethod = SMethod(
+    this, "encodeNbits", SFunc(Array(SGlobal, SBigInt), SLong), 6, EnDecodeNBitsCost)
+    .withIRInfo(MethodCallIrBuilder)
+    .withInfo(MethodCall, "Encode big integer number as nbits", ArgInfo("bigInt", "Big integer"))
+
+  lazy val decodeNBitsMethod: SMethod = SMethod(
+    this, "decodeNbits", SFunc(Array(SGlobal, SLong), SBigInt), 7, EnDecodeNBitsCost)
+    .withIRInfo(MethodCallIrBuilder)
+    .withInfo(MethodCall, "Decode nbits-encoded big integer number", ArgInfo("nbits", "NBits-encoded argument"))
+
   lazy val serializeMethod = SMethod(this, "serialize",
     SFunc(Array(SGlobal, tT), SByteArray, Array(paramT)), 3, DynamicCost)
       .withIRInfo(MethodCallIrBuilder)
@@ -1841,6 +1856,8 @@ case object SGlobalMethods extends MonoTypeMethods {
         groupGeneratorMethod,
         xorMethod,
         serializeMethod,
+        encodeNBitsMethod,
+        decodeNBitsMethod,
         fromBigEndianBytesMethod
       )
     } else {

data/shared/src/main/scala/sigma/data/CSigmaDslBuilder.scala

@@ -13,6 +13,7 @@ import sigma.eval.Extensions.EvalCollOps
 import sigma.serialization.{DataSerializer, GroupElementSerializer, SigmaSerializer}
 import sigma.serialization.{GroupElementSerializer, SerializerException, SigmaSerializer}
 import sigma.util.Extensions.BigIntegerOps
+import sigma.util.NBitsUtils
 import sigma.validation.SigmaValidationSettings
 import sigma.{AvlTree, BigInt, Box, Coll, CollBuilder, Evaluation, GroupElement, SigmaDslBuilder, SigmaProp, VersionContext}
 
@@ -178,6 +179,14 @@ class CSigmaDslBuilder extends SigmaDslBuilder { dsl =>
 
   override def groupGenerator: GroupElement = _generatorElement
 
+  def encodeNbits(bi: BigInt): Long = {
+    NBitsUtils.encodeCompactBits(bi.asInstanceOf[CBigInt].wrappedValue)
+  }
+
+  def decodeNbits(l: Long): BigInt = {
+    CBigInt(NBitsUtils.decodeCompactBits(l).bigInteger)
+  }
+
   /**
     * @return the identity of the Dlog group used in ErgoTree
     */

data/shared/src/main/scala/sigma/eval/ErgoTreeEvaluator.scala

@@ -59,9 +59,9 @@ abstract class ErgoTreeEvaluator {
     * @param opDesc   the operation descriptor to associate the cost with (when costTracingEnabled)
     * @param block    operation executed under the given cost
     */
-  def addFixedCost(costKind: FixedCost, opDesc: OperationDesc)(block: => Unit): Unit
+  def addFixedCost[R](costKind: FixedCost, opDesc: OperationDesc)(block: => R): R
 
-  def addFixedCost(costInfo: OperationCostInfo[FixedCost])(block: => Unit): Unit
+  def addFixedCost[R](costInfo: OperationCostInfo[FixedCost])(block: => R): R
 
   /** Adds the given cost to the `coster`. If tracing is enabled, creates a new cost item
     * with the given operation.

interpreter/shared/src/main/scala/sigmastate/interpreter/CErgoTreeEvaluator.scala

@@ -295,7 +295,7 @@ class CErgoTreeEvaluator(
   }
 
   /** @hotspot don't beautify the code */
-  override def addFixedCost(costKind: FixedCost, opDesc: OperationDesc)(block: => Unit): Unit = {
+  override def addFixedCost[R](costKind: FixedCost, opDesc: OperationDesc)(block: => R): R = {
     var costItem: FixedCostItem = null
     if (settings.costTracingEnabled) {
       costItem = FixedCostItem(opDesc, costKind)
@@ -307,16 +307,17 @@ class CErgoTreeEvaluator(
       }
       val start = System.nanoTime()
       coster.add(costKind.cost)
-      val _ = block
+      val res = block
       val end = System.nanoTime()
       profiler.addCostItem(costItem, end - start)
+      res
     } else {
       coster.add(costKind.cost)
       block
     }
   }
 
-  override def addFixedCost(costInfo: OperationCostInfo[FixedCost])(block: => Unit): Unit = {
+  override def addFixedCost[R](costInfo: OperationCostInfo[FixedCost])(block: => R): R = {
     addFixedCost(costInfo.costKind, costInfo.opDesc)(block)
   }
 

interpreter/shared/src/test/scala/sigma/serialization/MethodCallSerializerSpecification.scala

@@ -40,7 +40,7 @@ class MethodCallSerializerSpecification extends SerializationSpecification {
       code
     }
 
-    an[Exception] should be thrownBy (
+    an[SerializerException] should be thrownBy (
       VersionContext.withVersions((VersionContext.V6SoftForkVersion - 1).toByte, 1) {
         code
       }
@@ -68,4 +68,47 @@ class MethodCallSerializerSpecification extends SerializationSpecification {
       })
   }
 
+  property("MethodCall deserialization round trip for Global.encodeNBits") {
+    def code = {
+      val bi = BigIntConstant(5)
+      val expr = MethodCall(Global,
+        SGlobalMethods.encodeNBitsMethod,
+        Vector(bi),
+        Map()
+      )
+      roundTripTest(expr)
+    }
+
+    // should be ok
+    VersionContext.withVersions(VersionContext.V6SoftForkVersion, 1) {
+      code
+    }
+
+    an[ValidationException] should be thrownBy (
+      VersionContext.withVersions((VersionContext.V6SoftForkVersion - 1).toByte, 1) {
+        code
+      })
+  }
+
+  property("MethodCall deserialization round trip for Global.decodeNBits") {
+    def code = {
+      val l = LongConstant(5)
+      val expr = MethodCall(Global,
+        SGlobalMethods.decodeNBitsMethod,
+        Vector(l),
+        Map()
+      )
+      roundTripTest(expr)
+    }
+
+    VersionContext.withVersions(VersionContext.V6SoftForkVersion, 1) {
+      code
+    }
+
+    an[ValidationException] should be thrownBy (
+      VersionContext.withVersions((VersionContext.V6SoftForkVersion - 1).toByte, 1) {
+        code
+      }
+      )
+  }
 }

interpreter/shared/src/test/scala/sigmastate/eval/BasicOpsTests.scala

@@ -2,12 +2,17 @@ package sigmastate.eval
 
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
+import sigma.ast.{BigIntConstant, ErgoTree, Global, JitCost, MethodCall, SBigIntMethods, SGlobalMethods}
 import sigma.crypto.SecP256K1Group
-import sigma.data.{CSigmaDslBuilder => SigmaDsl, TrivialProp}
+import sigma.data.{CBigInt, TrivialProp}
+import sigma.eval.SigmaDsl
 import sigma.util.Extensions.SigmaBooleanOps
+import sigma.util.NBitsUtils
 
 import java.math.BigInteger
 import sigma.{ContractsTestkit, SigmaProp}
+import sigmastate.interpreter.{CErgoTreeEvaluator, CostAccumulator}
+import sigmastate.interpreter.CErgoTreeEvaluator.DefaultProfiler
 
 import scala.language.implicitConversions
 
@@ -63,4 +68,27 @@ class BasicOpsTests extends AnyFunSuite with ContractsTestkit with Matchers {
     box.creationInfo._1 shouldBe a [Integer]
   }
 
+  /**
+    * Checks BigInt.nbits evaluation for SigmaDSL as well as AST interpreter (MethodCall) layers
+    */
+  test("nbits evaluation") {
+    SigmaDsl.encodeNbits(CBigInt(BigInteger.valueOf(0))) should be
+      (NBitsUtils.encodeCompactBits(0))
+
+    val es = CErgoTreeEvaluator.DefaultEvalSettings
+    val accumulator = new CostAccumulator(
+      initialCost = JitCost(0),
+      costLimit = Some(JitCost.fromBlockCost(es.scriptCostLimitInEvaluator)))
+    val evaluator = new CErgoTreeEvaluator(
+      context = null,
+      constants = ErgoTree.EmptyConstants,
+      coster = accumulator, DefaultProfiler, es)
+
+    val res = MethodCall(Global, SGlobalMethods.encodeNBitsMethod, IndexedSeq(BigIntConstant(BigInteger.valueOf(0))), Map.empty)
+        .evalTo[Long](Map.empty)(evaluator)
+
+    res should be (NBitsUtils.encodeCompactBits(0))
+
+  }
+
 }

sc/shared/src/main/scala/sigma/compiler/ir/GraphBuilding.scala

@@ -9,6 +9,7 @@ import sigma.ast.syntax.{SValue, ValueOps}
 import sigma.ast._
 import sigma.compiler.ir.core.MutableLazy
 import sigma.crypto.EcPointType
+import sigma.VersionContext
 import sigma.data.ExactIntegral.{ByteIsExactIntegral, IntIsExactIntegral, LongIsExactIntegral, ShortIsExactIntegral}
 import sigma.data.ExactOrdering.{ByteIsExactOrdering, IntIsExactOrdering, LongIsExactOrdering, ShortIsExactOrdering}
 import sigma.data.{CSigmaDslBuilder, ExactIntegral, ExactNumeric, ExactOrdering, Lazy, Nullable}
@@ -1167,6 +1168,12 @@ trait GraphBuilding extends Base with DefRewriting { IR: IRContext =>
               val c1 = asRep[Coll[Byte]](argsV(0))
               val c2 = asRep[Coll[Byte]](argsV(1))
               g.xor(c1, c2)
+            case SGlobalMethods.encodeNBitsMethod.name if VersionContext.current.isV6SoftForkActivated =>
+              val c1 = asRep[BigInt](argsV(0))
+              g.encodeNbits(c1)
+            case SGlobalMethods.decodeNBitsMethod.name if VersionContext.current.isV6SoftForkActivated =>
+              val c1 = asRep[Long](argsV(0))
+              g.decodeNbits(c1)
             case SGlobalMethods.serializeMethod.name =>
               val value = asRep[Any](argsV(0))
               g.serialize(value)

sc/shared/src/main/scala/sigma/compiler/ir/GraphIRReflection.scala

@@ -1,5 +1,6 @@
 package sigma.compiler.ir
 
+import sigma.{BigInt, SigmaDslBuilder}
 import sigma.ast.SType
 import sigma.compiler.ir.primitives.Thunks
 import sigma.data.RType
@@ -528,6 +529,12 @@ object GraphIRReflection {
         mkMethod(clazz, "serialize", Array[Class[_]](classOf[Base#Ref[_]])) { (obj, args) =>
           obj.asInstanceOf[ctx.SigmaDslBuilder].serialize(args(0).asInstanceOf[ctx.Ref[Any]])
         },
+        mkMethod(clazz, "encodeNbits", Array[Class[_]](classOf[Base#Ref[_]])) { (obj, args) =>
+          obj.asInstanceOf[ctx.SigmaDslBuilder].encodeNbits(args(0).asInstanceOf[ctx.Ref[ctx.BigInt]])
+        },
+        mkMethod(clazz, "decodeNbits", Array[Class[_]](classOf[Base#Ref[_]])) { (obj, args) =>
+          obj.asInstanceOf[ctx.SigmaDslBuilder].decodeNbits(args(0).asInstanceOf[ctx.Ref[Long]])
+        },
         mkMethod(clazz, "fromBigEndianBytes", Array[Class[_]](classOf[Base#Ref[_]], classOf[TypeDescs#Elem[_]])) { (obj, args) =>
           obj.asInstanceOf[ctx.SigmaDslBuilder].fromBigEndianBytes(args(0).asInstanceOf[ctx.Ref[ctx.Coll[Byte]]])(args(1).asInstanceOf[ctx.Elem[SType]])
         }

sc/shared/src/main/scala/sigma/compiler/ir/wrappers/sigma/SigmaDslUnit.scala

@@ -115,6 +115,8 @@ import scalan._
       /** This method will be used in v6.0 to handle CreateAvlTree operation in GraphBuilding */
       def avlTree(operationFlags: Ref[Byte], digest: Ref[Coll[Byte]], keyLength: Ref[Int], valueLengthOpt: Ref[WOption[Int]]): Ref[AvlTree];
       def xor(l: Ref[Coll[Byte]], r: Ref[Coll[Byte]]): Ref[Coll[Byte]]
+      def encodeNbits(bi: Ref[BigInt]): Ref[Long]
+      def decodeNbits(l: Ref[Long]): Ref[BigInt]
       def serialize[T](value: Ref[T]): Ref[Coll[Byte]]
       def fromBigEndianBytes[T](bytes: Ref[Coll[Byte]])(implicit cT: Elem[T]): Ref[T]
     };

sc/shared/src/main/scala/sigma/compiler/ir/wrappers/sigma/impl/SigmaDslImpl.scala

@@ -1978,6 +1978,19 @@ object SigmaDslBuilder extends EntityObject("SigmaDslBuilder") {
         true, false, cT))
     }
 
+    override def encodeNbits(bi: Ref[BigInt]): Ref[Long] = {
+      asRep[Long](mkMethodCall(self,
+        SigmaDslBuilderClass.getMethod("encodeNbits", classOf[Sym]),
+        Array[AnyRef](bi),
+        true, false, element[Long]))
+    }
+
+    override def decodeNbits(l: Ref[Long]): Ref[BigInt] = {
+      asRep[BigInt](mkMethodCall(self,
+        SigmaDslBuilderClass.getMethod("decodeNbits", classOf[Sym]),
+        Array[AnyRef](l),
+        true, false, element[BigInt]))
+    }
   }
 
   implicit object LiftableSigmaDslBuilder
@@ -2151,6 +2164,20 @@ object SigmaDslBuilder extends EntityObject("SigmaDslBuilder") {
         Array[AnyRef](bytes, cT),
         true, true, cT, Map(tT -> Evaluation.rtypeToSType(cT.sourceType))))
     }
+
+    override def encodeNbits(bi: Ref[BigInt]): Ref[Long] = {
+      asRep[Long](mkMethodCall(source,
+        SigmaDslBuilderClass.getMethod("encodeNbits", classOf[Sym]),
+        Array[AnyRef](bi),
+        true, true, element[Long]))
+    }
+
+    override def decodeNbits(l: Ref[Long]): Ref[BigInt] = {
+      asRep[BigInt](mkMethodCall(source,
+        SigmaDslBuilderClass.getMethod("decodeNbits", classOf[Sym]),
+        Array[AnyRef](l),
+        true, true, element[BigInt]))
+    }
   }
 
   // entityUnref: single unref method for each type family
@@ -2168,9 +2195,9 @@ object SigmaDslBuilder extends EntityObject("SigmaDslBuilder") {
     override protected def collectMethods: Map[RMethod, MethodDesc] = {
       super.collectMethods ++
         Elem.declaredMethods(RClass(classOf[SigmaDslBuilder]), RClass(classOf[SSigmaDslBuilder]), Set(
-        "Colls", "verifyZK", "atLeast", "allOf", "allZK", "anyOf", "anyZK", "xorOf", "sigmaProp", "blake2b256", "sha256",
-          "byteArrayToBigInt", "longToByteArray", "byteArrayToLong", "proveDlog", "proveDHTuple", "groupGenerator", "substConstants",
-          "decodePoint", "avlTree", "xor", "serialize", "fromBigEndianBytes"
+        "Colls", "verifyZK", "atLeast", "allOf", "allZK", "anyOf", "anyZK", "xorOf", "sigmaProp", "blake2b256",
+          "sha256", "byteArrayToBigInt", "longToByteArray", "byteArrayToLong", "proveDlog", "proveDHTuple", "groupGenerator",
+          "substConstants", "decodePoint", "avlTree", "xor", "encodeNBits", "decodeNBits", "serialize", "fromBigEndianBytes"
         ))
     }
   }

sc/shared/src/test/scala/sigmastate/ErgoTreeSpecification.scala

@@ -517,7 +517,7 @@ class ErgoTreeSpecification extends SigmaDslTesting with ContractsTestkit with C
         MInfo(1, groupGeneratorMethod), MInfo(2, xorMethod)
       ) ++ (if (isV6Activated) {
         // id = 4 reserved for deserializeTo method
-        Seq(MInfo(3, serializeMethod), MInfo(5, fromBigEndianBytesMethod)) // methods added in v6.0
+        Seq(MInfo(3, serializeMethod), MInfo(5, fromBigEndianBytesMethod), MInfo(6, encodeNBitsMethod), MInfo(7, decodeNBitsMethod)) // methods added in v6.0
       } else {
         Seq.empty[MInfo]
       }), true)