wip

vendor/github.com/antonmedv/expr/vm/vm.go

@@ -0,0 +1,439 @@
+package vm
+
+import (
+	"fmt"
+	"reflect"
+	"regexp"
+	"strings"
+
+	"github.com/antonmedv/expr/file"
+)
+
+var (
+	MemoryBudget int = 1e6
+)
+
+func Run(program *Program, env interface{}) (interface{}, error) {
+	if program == nil {
+		return nil, fmt.Errorf("program is nil")
+	}
+
+	vm := VM{}
+	return vm.Run(program, env)
+}
+
+type VM struct {
+	stack     []interface{}
+	constants []interface{}
+	bytecode  []byte
+	ip        int
+	pp        int
+	scopes    []Scope
+	debug     bool
+	step      chan struct{}
+	curr      chan int
+	memory    int
+	limit     int
+}
+
+func Debug() *VM {
+	vm := &VM{
+		debug: true,
+		step:  make(chan struct{}, 0),
+		curr:  make(chan int, 0),
+	}
+	return vm
+}
+
+func (vm *VM) Run(program *Program, env interface{}) (out interface{}, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			f := &file.Error{
+				Location: program.Locations[vm.pp],
+				Message:  fmt.Sprintf("%v", r),
+			}
+			err = f.Bind(program.Source)
+		}
+	}()
+
+	vm.limit = MemoryBudget
+	vm.ip = 0
+	vm.pp = 0
+
+	if vm.stack == nil {
+		vm.stack = make([]interface{}, 0, 2)
+	} else {
+		vm.stack = vm.stack[0:0]
+	}
+
+	if vm.scopes != nil {
+		vm.scopes = vm.scopes[0:0]
+	}
+
+	vm.bytecode = program.Bytecode
+	vm.constants = program.Constants
+
+	for vm.ip < len(vm.bytecode) {
+
+		if vm.debug {
+			<-vm.step
+		}
+
+		vm.pp = vm.ip
+		vm.ip++
+		op := vm.bytecode[vm.pp]
+
+		switch op {
+
+		case OpPush:
+			vm.push(vm.constant())
+
+		case OpPop:
+			vm.pop()
+
+		case OpRot:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(b)
+			vm.push(a)
+
+		case OpFetch:
+			vm.push(fetch(env, vm.constant()))
+
+		case OpFetchMap:
+			vm.push(env.(map[string]interface{})[vm.constant().(string)])
+
+		case OpTrue:
+			vm.push(true)
+
+		case OpFalse:
+			vm.push(false)
+
+		case OpNil:
+			vm.push(nil)
+
+		case OpNegate:
+			v := negate(vm.pop())
+			vm.push(v)
+
+		case OpNot:
+			v := vm.pop().(bool)
+			vm.push(!v)
+
+		case OpEqual:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(equal(a, b))
+
+		case OpEqualInt:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(a.(int) == b.(int))
+
+		case OpEqualString:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(a.(string) == b.(string))
+
+		case OpJump:
+			offset := vm.arg()
+			vm.ip += int(offset)
+
+		case OpJumpIfTrue:
+			offset := vm.arg()
+			if vm.current().(bool) {
+				vm.ip += int(offset)
+			}
+
+		case OpJumpIfFalse:
+			offset := vm.arg()
+			if !vm.current().(bool) {
+				vm.ip += int(offset)
+			}
+
+		case OpJumpBackward:
+			offset := vm.arg()
+			vm.ip -= int(offset)
+
+		case OpIn:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(in(a, b))
+
+		case OpLess:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(less(a, b))
+
+		case OpMore:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(more(a, b))
+
+		case OpLessOrEqual:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(lessOrEqual(a, b))
+
+		case OpMoreOrEqual:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(moreOrEqual(a, b))
+
+		case OpAdd:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(add(a, b))
+
+		case OpSubtract:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(subtract(a, b))
+
+		case OpMultiply:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(multiply(a, b))
+
+		case OpDivide:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(divide(a, b))
+
+		case OpModulo:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(modulo(a, b))
+
+		case OpExponent:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(exponent(a, b))
+
+		case OpRange:
+			b := vm.pop()
+			a := vm.pop()
+			min := toInt(a)
+			max := toInt(b)
+			size := max - min + 1
+			if vm.memory+size >= vm.limit {
+				panic("memory budget exceeded")
+			}
+			vm.push(makeRange(min, max))
+			vm.memory += size
+
+		case OpMatches:
+			b := vm.pop()
+			a := vm.pop()
+			match, err := regexp.MatchString(b.(string), a.(string))
+			if err != nil {
+				panic(err)
+			}
+
+			vm.push(match)
+
+		case OpMatchesConst:
+			a := vm.pop()
+			r := vm.constant().(*regexp.Regexp)
+			vm.push(r.MatchString(a.(string)))
+
+		case OpContains:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(strings.Contains(a.(string), b.(string)))
+
+		case OpStartsWith:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(strings.HasPrefix(a.(string), b.(string)))
+
+		case OpEndsWith:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(strings.HasSuffix(a.(string), b.(string)))
+
+		case OpIndex:
+			b := vm.pop()
+			a := vm.pop()
+			vm.push(fetch(a, b))
+
+		case OpSlice:
+			from := vm.pop()
+			to := vm.pop()
+			node := vm.pop()
+			vm.push(slice(node, from, to))
+
+		case OpProperty:
+			a := vm.pop()
+			b := vm.constant()
+			vm.push(fetch(a, b))
+
+		case OpCall:
+			call := vm.constant().(Call)
+			in := make([]reflect.Value, call.Size)
+			for i := call.Size - 1; i >= 0; i-- {
+				param := vm.pop()
+				if param == nil && reflect.TypeOf(param) == nil {
+					// In case of nil value and nil type use this hack,
+					// otherwise reflect.Call will panic on zero value.
+					in[i] = reflect.ValueOf(&param).Elem()
+				} else {
+					in[i] = reflect.ValueOf(param)
+				}
+			}
+			out := FetchFn(env, call.Name).Call(in)
+			vm.push(out[0].Interface())
+
+		case OpCallFast:
+			call := vm.constant().(Call)
+			in := make([]interface{}, call.Size)
+			for i := call.Size - 1; i >= 0; i-- {
+				in[i] = vm.pop()
+			}
+			fn := FetchFn(env, call.Name).Interface()
+			vm.push(fn.(func(...interface{}) interface{})(in...))
+
+		case OpMethod:
+			call := vm.constants[vm.arg()].(Call)
+			in := make([]reflect.Value, call.Size)
+			for i := call.Size - 1; i >= 0; i-- {
+				param := vm.pop()
+				if param == nil && reflect.TypeOf(param) == nil {
+					// In case of nil value and nil type use this hack,
+					// otherwise reflect.Call will panic on zero value.
+					in[i] = reflect.ValueOf(&param).Elem()
+				} else {
+					in[i] = reflect.ValueOf(param)
+				}
+			}
+			out := FetchFn(vm.pop(), call.Name).Call(in)
+			vm.push(out[0].Interface())
+
+		case OpArray:
+			size := vm.pop().(int)
+			array := make([]interface{}, size)
+			for i := size - 1; i >= 0; i-- {
+				array[i] = vm.pop()
+			}
+			vm.push(array)
+			vm.memory += size
+			if vm.memory >= vm.limit {
+				panic("memory budget exceeded")
+			}
+
+		case OpMap:
+			size := vm.pop().(int)
+			m := make(map[string]interface{})
+			for i := size - 1; i >= 0; i-- {
+				value := vm.pop()
+				key := vm.pop()
+				m[key.(string)] = value
+			}
+			vm.push(m)
+			vm.memory += size
+			if vm.memory >= vm.limit {
+				panic("memory budget exceeded")
+			}
+
+		case OpLen:
+			vm.push(length(vm.current()))
+
+		case OpCast:
+			t := vm.arg()
+			switch t {
+			case 0:
+				vm.push(toInt64(vm.pop()))
+			case 1:
+				vm.push(toFloat64(vm.pop()))
+			}
+
+		case OpStore:
+			scope := vm.Scope()
+			key := vm.constant().(string)
+			value := vm.pop()
+			scope[key] = value
+
+		case OpLoad:
+			scope := vm.Scope()
+			key := vm.constant().(string)
+			vm.push(scope[key])
+
+		case OpInc:
+			scope := vm.Scope()
+			key := vm.constant().(string)
+			i := scope[key].(int)
+			i++
+			scope[key] = i
+
+		case OpBegin:
+			scope := make(Scope)
+			vm.scopes = append(vm.scopes, scope)
+
+		case OpEnd:
+			vm.scopes = vm.scopes[:len(vm.scopes)-1]
+
+		default:
+			panic(fmt.Sprintf("unknown bytecode %#x", op))
+		}
+
+		if vm.debug {
+			vm.curr <- vm.ip
+		}
+	}
+
+	if vm.debug {
+		close(vm.curr)
+		close(vm.step)
+	}
+
+	if len(vm.stack) > 0 {
+		return vm.pop(), nil
+	}
+
+	return nil, nil
+}
+
+func (vm *VM) push(value interface{}) {
+	vm.stack = append(vm.stack, value)
+}
+
+func (vm *VM) current() interface{} {
+	return vm.stack[len(vm.stack)-1]
+}
+
+func (vm *VM) pop() interface{} {
+	value := vm.stack[len(vm.stack)-1]
+	vm.stack = vm.stack[:len(vm.stack)-1]
+	return value
+}
+
+func (vm *VM) arg() uint16 {
+	b0, b1 := vm.bytecode[vm.ip], vm.bytecode[vm.ip+1]
+	vm.ip += 2
+	return uint16(b0) | uint16(b1)<<8
+}
+
+func (vm *VM) constant() interface{} {
+	return vm.constants[vm.arg()]
+}
+
+func (vm *VM) Stack() []interface{} {
+	return vm.stack
+}
+
+func (vm *VM) Scope() Scope {
+	if len(vm.scopes) > 0 {
+		return vm.scopes[len(vm.scopes)-1]
+	}
+	return nil
+}
+
+func (vm *VM) Step() {
+	if vm.ip < len(vm.bytecode) {
+		vm.step <- struct{}{}
+	}
+}
+
+func (vm *VM) Position() chan int {
+	return vm.curr
+}