Add import host function

internal/polkavm/host_call/common.go

@@ -24,6 +24,7 @@ const (
 	SolicitCost
 	ForgetCost
 	HistoricalLookupCost
+	ImportCost
 )
 
 const (
@@ -43,6 +44,7 @@ const (
 	SolicitID
 	ForgetID
 	HistoricalLookupID
+	ImportID
 )
 
 type Code uint64

internal/polkavm/host_call/refine_functions.go

@@ -4,13 +4,14 @@ import (
 	"math"
 
 	"github.com/eigerco/strawberry/internal/block"
+	"github.com/eigerco/strawberry/internal/common"
 	"github.com/eigerco/strawberry/internal/crypto"
 	"github.com/eigerco/strawberry/internal/jamtime"
 	. "github.com/eigerco/strawberry/internal/polkavm"
 	"github.com/eigerco/strawberry/internal/service"
 )
 
-// HistoricalLookup ΩH(ϱ, ω, µ, (m, e), s,d, t)
+// HistoricalLookup ΩH(ϱ, ω, µ, (m, e), s, d, t)
 func HistoricalLookup(
 	gas Gas,
 	regs Registers,
@@ -53,8 +54,7 @@ func HistoricalLookup(
 	v := a.LookupPreimage(t, h)
 
 	if len(v) == 0 {
-		regs[A0] = uint64(NONE)
-		return gas, regs, mem, ctxPair, nil
+		return gas, withCode(regs, NONE), mem, ctxPair, nil
 	}
 
 	if uint64(len(v)) > bz {
@@ -70,3 +70,39 @@ func HistoricalLookup(
 
 	return gas, regs, mem, ctxPair, nil
 }
+
+// Import ΩY(ϱ, ω, µ, (m, e), i)
+func Import(
+	gas Gas,
+	regs Registers,
+	mem Memory,
+	ctxPair RefineContextPair,
+	importedSegments []Segment,
+) (Gas, Registers, Memory, RefineContextPair, error) {
+	if gas < ImportCost {
+		return gas, regs, mem, ctxPair, ErrOutOfGas
+	}
+	gas -= ImportCost
+
+	index := regs[A0]  // ω7
+	offset := regs[A1] // ω8
+	length := regs[A2] // ω9
+
+	// v = ∅
+	if index >= uint64(len(importedSegments)) {
+		// v = ∅, return NONE
+		return gas, withCode(regs, NONE), mem, ctxPair, nil
+	}
+
+	// v = i[ω7]
+	v := importedSegments[index][:]
+
+	l := min(length, common.SizeOfSegment)
+
+	segmentToWrite := v[:l]
+	if err := mem.Write(uint32(offset), segmentToWrite); err != nil {
+		return gas, withCode(regs, OOB), mem, ctxPair, nil
+	}
+
+	return gas, withCode(regs, OK), mem, ctxPair, nil
+}

internal/polkavm/host_call/refine_functions_test.go

@@ -7,6 +7,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"github.com/eigerco/strawberry/internal/block"
+	"github.com/eigerco/strawberry/internal/common"
 	"github.com/eigerco/strawberry/internal/crypto"
 	"github.com/eigerco/strawberry/internal/jamtime"
 	"github.com/eigerco/strawberry/internal/polkavm"
@@ -104,3 +105,66 @@ func TestHistoricalLookup(t *testing.T) {
 	expectedGasRemaining := polkavm.Gas(initialGas) - host_call.HistoricalLookupCost - polkavm.GasCosts[polkavm.Ecalli] - polkavm.GasCosts[polkavm.JumpIndirect]
 	assert.Equal(t, expectedGasRemaining, gasRemaining)
 }
+
+func TestImport(t *testing.T) {
+	pp := &polkavm.Program{
+		Instructions: []polkavm.Instruction{
+			{Opcode: polkavm.Ecalli, Imm: []uint32{0}, Offset: 0, Length: 1},
+			{Opcode: polkavm.JumpIndirect, Imm: []uint32{0}, Reg: []polkavm.Reg{polkavm.RA}, Offset: 1, Length: 2},
+		},
+	}
+
+	memoryMap, err := polkavm.NewMemoryMap(0, 256, 512, 0)
+	require.NoError(t, err)
+
+	initialGas := uint64(100)
+
+	segmentData := [common.SizeOfSegment]byte{}
+	for i := range segmentData {
+		segmentData[i] = byte('A')
+	}
+	importedSegments := []polkavm.Segment{segmentData}
+
+	bo := memoryMap.RWDataAddress + 100
+	bz := uint32(50)
+
+	initialRegs := polkavm.Registers{
+		polkavm.RA: polkavm.VmAddressReturnToHost,
+		polkavm.SP: uint64(memoryMap.StackAddressHigh),
+		polkavm.A0: uint64(0),
+		polkavm.A1: uint64(bo),
+		polkavm.A2: uint64(bz),
+	}
+
+	mem := memoryMap.NewMemory(nil, nil, nil)
+
+	hostCall := func(hostCall uint32, gasCounter polkavm.Gas, regs polkavm.Registers, mem polkavm.Memory, x service.ServiceAccount) (polkavm.Gas, polkavm.Registers, polkavm.Memory, service.ServiceAccount, error) {
+		gasCounterOut, regsOut, memOut, _, err := host_call.Import(
+			gasCounter,
+			regs,
+			mem,
+			polkavm.RefineContextPair{},
+			importedSegments,
+		)
+		require.NoError(t, err)
+		return gasCounterOut, regsOut, memOut, x, err
+	}
+
+	gasRemaining, regsOut, memOut, _, err := interpreter.InvokeHostCall(pp, memoryMap, 0, initialGas, initialRegs, mem, hostCall, service.ServiceAccount{})
+	require.ErrorIs(t, err, polkavm.ErrHalt)
+
+	actualValue := make([]byte, bz)
+	err = memOut.Read(bo, actualValue)
+	require.NoError(t, err)
+
+	expectedData := make([]byte, bz)
+	for i := range expectedData {
+		expectedData[i] = 'A'
+	}
+
+	assert.Equal(t, expectedData, actualValue)
+	assert.Equal(t, uint64(host_call.OK), regsOut[polkavm.A0])
+
+	expectedGasRemaining := polkavm.Gas(initialGas) - host_call.ImportCost - polkavm.GasCosts[polkavm.Ecalli] - polkavm.GasCosts[polkavm.JumpIndirect]
+	assert.Equal(t, expectedGasRemaining, gasRemaining)
+}