core: vm: sqlvm: add built-in function RAND()

2 files changed, 91 insertions, 0 deletions

diff --git a/core/vm/sqlvm/runtime/functions.go b/core/vm/sqlvm/runtime/functions.go
index d72ee5bd8..d9c0f94f4 100644
--- a/core/vm/sqlvm/runtime/functions.go
+++ b/core/vm/sqlvm/runtime/functions.go
@@ -1,6 +1,7 @@
 package runtime
 
 import (
+	"encoding/binary"
 	"fmt"
 	"math"
 
@@ -10,6 +11,7 @@ import (
 	"github.com/dexon-foundation/dexon/core/vm/sqlvm/common"
 	dec "github.com/dexon-foundation/dexon/core/vm/sqlvm/common/decimal"
 	se "github.com/dexon-foundation/dexon/core/vm/sqlvm/errors"
+	"github.com/dexon-foundation/dexon/crypto"
 )
 
 // function identifier
@@ -23,6 +25,7 @@ const (
 	MSGDATA        = "MSG_DATA"
 	TXORIGIN       = "TX_ORIGIN"
 	NOW            = "NOW"
+	RAND           = "RAND"
 )
 
 type fn func(*common.Context, []*Operand, uint64) (*Operand, error)
@@ -38,6 +41,7 @@ var (
 		MSGSENDER:      fnMsgSender,
 		MSGDATA:        fnMsgData,
 		TXORIGIN:       fnTxOrigin,
+		RAND:           fnRand,
 	}
 )
 
@@ -165,3 +169,31 @@ func fnTxOrigin(ctx *common.Context, ops []*Operand, length uint64) (result *Ope
 	return
 }
 
+func fnRand(ctx *common.Context, ops []*Operand, length uint64) (result *Operand, err error) {
+	binaryOriginNonce := make([]byte, binary.MaxVarintLen64)
+	binary.PutUvarint(binaryOriginNonce, ctx.Storage.GetNonce(ctx.Origin))
+
+	binaryUsedIndex := make([]byte, binary.MaxVarintLen64)
+	vType := ast.ComposeDataType(ast.DataTypeMajorUint, 31)
+
+	fn := func() *Raw {
+		binary.PutUvarint(binaryUsedIndex, ctx.RandCallIndex)
+		ctx.RandCallIndex++
+
+		hash := crypto.Keccak256(
+			ctx.Randomness,
+			ctx.Origin.Bytes(),
+			binaryOriginNonce,
+			binaryUsedIndex)
+
+		v, _ := ast.DecimalDecode(vType, hash)
+		return &Raw{Value: v}
+	}
+
+	result = assignFuncResult(
+		[]ast.DataType{ast.ComposeDataType(ast.DataTypeMajorUint, 31)},
+		fn, length,
+	)
+	return
+
+}
diff --git a/core/vm/sqlvm/runtime/functions_test.go b/core/vm/sqlvm/runtime/functions_test.go
index 54fa75816..828c43efa 100644
--- a/core/vm/sqlvm/runtime/functions_test.go
+++ b/core/vm/sqlvm/runtime/functions_test.go
@@ -463,3 +463,62 @@ func (s *FunctionSuite) TestFnTxOrigin() {
 	}
 }
 
+func (s *FunctionSuite) TestFnRand() {
+	type blockRandCase struct {
+		Name   string
+		Origin dexCommon.Address
+		Length uint64
+		Err    error
+	}
+
+	res := []byte{
+		0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef,
+		0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef,
+		0x01, 0x23, 0x45, 0x67}
+	address := dexCommon.BytesToAddress(res)
+
+	testcases := []blockRandCase{
+		{"address with length 100", address, 100, nil},
+		{"address with length 0", address, 0, nil},
+	}
+
+	callFn := func(c blockRandCase) (*Operand, error) {
+		return fnRand(
+			&common.Context{
+				Context: vm.Context{Origin: c.Origin, Randomness: res},
+				Storage: newStorage(),
+			},
+			nil,
+			c.Length)
+	}
+
+	meta := []ast.DataType{ast.ComposeDataType(ast.DataTypeMajorUint, 31)}
+
+	for idx, tCase := range testcases {
+		r, err := callFn(tCase)
+		s.Require().Equal(
+			tCase.Err, err,
+			"Index: %v. Error not expected: %v != %v", idx, tCase.Err, err)
+		s.Require().Equal(
+			meta, r.Meta,
+			"Index: %v. Meta not equal: %v != %v", idx, meta, r.Meta)
+		s.Require().Equal(
+			uint64(len(r.Data)), tCase.Length,
+			"Index: %v. Length not equal: %v != %v", idx, len(r.Data), tCase.Length)
+
+		var (
+			fmap = make(map[string]struct{})
+			ok   bool
+			key  string
+		)
+
+		for i := 0; i < len(r.Data); i++ {
+			key = r.Data[i].String()
+			_, ok = fmap[key]
+			s.Require().False(
+				ok,
+				"Duplicate rand: %v\nmap: %v\ndata: %v", key, fmap, r.Data)
+			fmap[key] = struct{}{}
+		}
+	}
+}