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vm.go
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vm.go
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package exec
import (
"fmt"
flatbuffers "github.com/google/flatbuffers/go"
"github.com/pkg/errors"
"github.com/regeda/expr/bytecode"
"github.com/regeda/expr/compiler"
"github.com/regeda/expr/delegate"
"github.com/regeda/expr/memory"
)
type VM struct {
globals Globals
memory memory.Memory
stack stack
prog bytecode.Program
}
type Opt func(*VM)
func WithMemory(m memory.Memory) Opt {
return func(vm *VM) {
vm.memory = m
}
}
func WithStackSize(n uint32) Opt {
return func(vm *VM) {
vm.stack = make(stack, 0, n)
}
}
func WithRegistry(reg delegate.Registry) Opt {
return func(vm *VM) {
vm.globals.SetRegistry(reg)
}
}
func New(opts ...Opt) *VM {
vm := &VM{}
for _, opt := range opts {
opt(vm)
}
return vm
}
func (v *VM) reset() {
v.memory.Reset()
v.stack.reset()
}
func (v *VM) checkVersion() error {
var ver bytecode.Version
if v.prog.Ver(&ver) == nil {
return errNoVersion
}
majorVer := ver.Major()
if majorVer > compiler.MajorVersion {
return fmt.Errorf("bytecode version %d is not supported, compiler version %d", majorVer, compiler.MajorVersion)
}
return nil
}
func (v *VM) terminate() (memory.Addr, error) {
val, err := v.stack.pop(1)
if err != nil {
return memory.Nil, err
}
return val[0], nil
}
func (v *VM) Exec(bcode []byte) (memory.Addr, error) {
v.reset()
v.prog.Init(bcode, flatbuffers.GetUOffsetT(bcode))
if err := v.checkVersion(); err != nil {
return memory.Nil, err
}
framesLen := v.prog.FramesLength()
if framesLen == 0 {
return memory.Nil, errNoFrames
}
var frame bytecode.Frame
for i := 0; i < framesLen; i++ {
if !v.prog.Frames(&frame, i) {
return memory.Nil, errUnexpectedEOF
}
addr, err := v.execFrame(&frame)
if err != nil {
return memory.Nil, errors.Wrapf(err, "failed to exec frame at %d", i)
}
v.stack.push(addr)
}
return v.terminate()
}
func (v *VM) popType(n uint32, t memory.Type) ([]memory.Addr, error) {
argv, err := v.stack.pop(n)
if err != nil {
return nil, err
}
for _, arg := range argv {
if !arg.TypeOf(t) {
return nil, fmt.Errorf("unexpected type %v instead of %v", arg.Type(), t)
}
}
return argv, nil
}
func (v *VM) execFrame(frame *bytecode.Frame) (memory.Addr, error) {
opType := frame.OpType()
switch opType {
case bytecode.OpOpPushTrue:
return memory.True, nil
case bytecode.OpOpPushFalse:
return memory.False, nil
case bytecode.OpOpAdd:
argv, err := v.popType(2, memory.TypeInt64)
if err != nil {
return memory.Nil, err
}
return v.memory.AllocInt64(argv[0].Int64() + argv[1].Int64()), nil
case bytecode.OpOpSub:
argv, err := v.popType(2, memory.TypeInt64)
if err != nil {
return memory.Nil, err
}
return v.memory.AllocInt64(argv[0].Int64() - argv[1].Int64()), nil
case bytecode.OpOpMul:
argv, err := v.popType(2, memory.TypeInt64)
if err != nil {
return memory.Nil, err
}
return v.memory.AllocInt64(argv[0].Int64() * argv[1].Int64()), nil
case bytecode.OpOpDiv:
argv, err := v.popType(2, memory.TypeInt64)
if err != nil {
return memory.Nil, err
}
div := argv[1].Int64()
if div == 0 {
return memory.Nil, errDivByZero
}
return v.memory.AllocInt64(argv[0].Int64() / div), nil
case bytecode.OpOpPushStr:
var tab flatbuffers.Table
if !frame.Op(&tab) {
return memory.Nil, errNoOperation
}
var op bytecode.OpPushStr
op.Init(tab.Bytes, tab.Pos)
return v.memory.AllocBytesAddr(op.Val()), nil
case bytecode.OpOpPushInt:
var tab flatbuffers.Table
if !frame.Op(&tab) {
return memory.Nil, errNoOperation
}
var op bytecode.OpPushInt
op.Init(tab.Bytes, tab.Pos)
return v.memory.AllocInt64(op.Val()), nil
case bytecode.OpOpPushVector:
var tab flatbuffers.Table
if !frame.Op(&tab) {
return memory.Nil, errNoOperation
}
var op bytecode.OpPushVector
op.Init(tab.Bytes, tab.Pos)
elems, err := v.stack.pop(uint32(op.Elems()))
if err != nil {
return memory.Nil, err
}
return v.memory.CopyVector(elems...), nil
case bytecode.OpOpInvoke:
var tab flatbuffers.Table
if !frame.Op(&tab) {
return memory.Nil, errNoOperation
}
var op bytecode.OpInvoke
op.Init(tab.Bytes, tab.Pos)
fn := op.Name()
if fn == nil {
return memory.Nil, errEmptyDelegatorName
}
delegator, ok := v.globals.delegators.Get(string(fn))
if !ok {
return memory.Nil, fmt.Errorf("delegator <%s> not exists", fn)
}
args := op.Args()
argv, err := v.stack.pop(uint32(args))
if err != nil {
return memory.Nil, err
}
return delegator.Delegate(&v.memory, argv)
default:
return memory.Nil, fmt.Errorf("unexpected frame type %s", opType)
}
}