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extract.go
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extract.go
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package pogs
import (
"errors"
"fmt"
"math"
"reflect"
"github.com/zombiezen/mcm/third_party/golang/capnproto"
"github.com/zombiezen/mcm/third_party/golang/capnproto/internal/nodemap"
"github.com/zombiezen/mcm/third_party/golang/capnproto/std/capnp/schema_bootstrap"
)
// Extract copies s into val, a pointer to a Go struct.
func Extract(val interface{}, typeID uint64, s capnp.Struct) error {
e := new(extracter)
err := e.extractStruct(reflect.ValueOf(val), typeID, s)
if err != nil {
return fmt.Errorf("pogs: extract @%#x: %v", typeID, err)
}
return nil
}
type extracter struct {
nodes nodemap.Map
}
func (e *extracter) extractStruct(val reflect.Value, typeID uint64, s capnp.Struct) error {
if val.Kind() == reflect.Ptr {
if val.Type().Elem().Kind() != reflect.Struct {
return fmt.Errorf("can't extract struct into %v", val.Type())
}
switch {
case !val.CanSet() && val.IsNil():
// Even if the Cap'n Proto pointer isn't valid, this is probably
// the caller's fault and will be a bug at some point.
return errors.New("can't extract struct into nil")
case !s.IsValid() && val.CanSet():
val.Set(reflect.Zero(val.Type()))
return nil
case s.IsValid() && val.CanSet() && val.IsNil():
val.Set(reflect.New(val.Type().Elem()))
}
val = val.Elem()
} else if val.Kind() != reflect.Struct {
return fmt.Errorf("can't extract struct into %v", val.Type())
}
if !val.CanSet() {
return errors.New("can't modify struct, did you pass in a pointer to your struct?")
}
n, err := e.nodes.Find(typeID)
if err != nil {
return err
}
if !n.IsValid() || n.Which() != schema.Node_Which_structNode {
return fmt.Errorf("cannot find struct type %#x", typeID)
}
props, err := mapStruct(val.Type(), n)
if err != nil {
return fmt.Errorf("can't extract %s: %v", val.Type(), err)
}
var discriminant uint16
hasWhich := false
if hasDiscriminant(n) {
discriminant = s.Uint16(capnp.DataOffset(n.StructNode().DiscriminantOffset() * 2))
if err := props.setWhich(val, discriminant); err == nil {
hasWhich = true
} else if !isNoWhichError(err) {
return err
}
}
fields, err := n.StructNode().Fields()
if err != nil {
return err
}
for i := 0; i < fields.Len(); i++ {
f := fields.At(i)
vf := props.makeFieldByOrdinal(val, i)
if !vf.IsValid() {
// Don't have a field for this.
continue
}
if dv := f.DiscriminantValue(); dv != schema.Field_noDiscriminant {
if !hasWhich {
return fmt.Errorf("can't extract %s into %v: has union field but no Which field", shortDisplayName(n), val.Type())
}
if dv != discriminant {
continue
}
}
switch f.Which() {
case schema.Field_Which_slot:
if err := e.extractField(vf, s, f); err != nil {
return err
}
case schema.Field_Which_group:
if err := e.extractStruct(vf, f.Group().TypeId(), s); err != nil {
return err
}
}
}
return nil
}
func (e *extracter) extractField(val reflect.Value, s capnp.Struct, f schema.Field) error {
typ, err := f.Slot().Type()
if err != nil {
return err
}
dv, err := f.Slot().DefaultValue()
if err != nil {
return err
}
if dv.IsValid() && int(typ.Which()) != int(dv.Which()) {
name, _ := f.NameBytes()
return fmt.Errorf("extract field %s: default value is a %v, want %v", name, dv.Which(), typ.Which())
}
if !isTypeMatch(val.Type(), typ) {
name, _ := f.NameBytes()
return fmt.Errorf("can't extract field %s of type %v into a Go %v", name, typ.Which(), val.Type())
}
switch typ.Which() {
case schema.Type_Which_bool:
v := s.Bit(capnp.BitOffset(f.Slot().Offset()))
d := dv.Bool()
val.SetBool(v != d) // != acts as XOR
case schema.Type_Which_int8:
v := int8(s.Uint8(capnp.DataOffset(f.Slot().Offset())))
d := dv.Int8()
val.SetInt(int64(v ^ d))
case schema.Type_Which_int16:
v := int16(s.Uint16(capnp.DataOffset(f.Slot().Offset() * 2)))
d := dv.Int16()
val.SetInt(int64(v ^ d))
case schema.Type_Which_int32:
v := int32(s.Uint32(capnp.DataOffset(f.Slot().Offset() * 4)))
d := dv.Int32()
val.SetInt(int64(v ^ d))
case schema.Type_Which_int64:
v := int64(s.Uint64(capnp.DataOffset(f.Slot().Offset() * 8)))
d := dv.Int64()
val.SetInt(v ^ d)
case schema.Type_Which_uint8:
v := s.Uint8(capnp.DataOffset(f.Slot().Offset()))
d := dv.Uint8()
val.SetUint(uint64(v ^ d))
case schema.Type_Which_uint16:
v := s.Uint16(capnp.DataOffset(f.Slot().Offset() * 2))
d := dv.Uint16()
val.SetUint(uint64(v ^ d))
case schema.Type_Which_enum:
v := s.Uint16(capnp.DataOffset(f.Slot().Offset() * 2))
d := dv.Enum()
val.SetUint(uint64(v ^ d))
case schema.Type_Which_uint32:
v := s.Uint32(capnp.DataOffset(f.Slot().Offset() * 4))
d := dv.Uint32()
val.SetUint(uint64(v ^ d))
case schema.Type_Which_uint64:
v := s.Uint64(capnp.DataOffset(f.Slot().Offset() * 8))
d := dv.Uint64()
val.SetUint(v ^ d)
case schema.Type_Which_float32:
v := s.Uint32(capnp.DataOffset(f.Slot().Offset() * 4))
d := math.Float32bits(dv.Float32())
val.SetFloat(float64(math.Float32frombits(v ^ d)))
case schema.Type_Which_float64:
v := s.Uint64(capnp.DataOffset(f.Slot().Offset() * 8))
d := math.Float64bits(dv.Float64())
val.SetFloat(math.Float64frombits(v ^ d))
case schema.Type_Which_text:
p, err := s.Ptr(uint16(f.Slot().Offset()))
if err != nil {
return err
}
var b []byte
if p.IsValid() {
b = p.TextBytes()
} else {
b, _ = dv.TextBytes()
}
if val.Kind() == reflect.String {
val.SetString(string(b))
} else {
// byte slice, as guaranteed by isTypeMatch
val.SetBytes(b)
}
case schema.Type_Which_data:
p, err := s.Ptr(uint16(f.Slot().Offset()))
if err != nil {
return err
}
var b []byte
if p.IsValid() {
b = p.Data()
} else {
b, _ = dv.Data()
}
val.SetBytes(b)
case schema.Type_Which_structType:
p, err := s.Ptr(uint16(f.Slot().Offset()))
if err != nil {
return err
}
ss := p.Struct()
if !ss.IsValid() {
p, _ = dv.StructValuePtr()
ss = p.Struct()
}
return e.extractStruct(val, typ.StructType().TypeId(), ss)
case schema.Type_Which_list:
p, err := s.Ptr(uint16(f.Slot().Offset()))
if err != nil {
return err
}
l := p.List()
if !l.IsValid() {
p, _ = dv.ListPtr()
l = p.List()
}
return e.extractList(val, typ, l)
default:
return fmt.Errorf("unknown field type %v", typ.Which())
}
return nil
}
func (e *extracter) extractList(val reflect.Value, typ schema.Type, l capnp.List) error {
vt := val.Type()
elem, err := typ.List().ElementType()
if err != nil {
return err
}
if !isTypeMatch(vt, typ) {
// TODO(light): the error won't be that useful for nested lists.
return fmt.Errorf("can't extract %v list into a Go %v", elem.Which(), vt)
}
if !l.IsValid() {
val.Set(reflect.Zero(vt))
return nil
}
n := l.Len()
val.Set(reflect.MakeSlice(vt, n, n))
switch elem.Which() {
case schema.Type_Which_bool:
for i := 0; i < n; i++ {
val.Index(i).SetBool(capnp.BitList{List: l}.At(i))
}
case schema.Type_Which_int8:
for i := 0; i < n; i++ {
val.Index(i).SetInt(int64(capnp.Int8List{List: l}.At(i)))
}
case schema.Type_Which_int16:
for i := 0; i < n; i++ {
val.Index(i).SetInt(int64(capnp.Int16List{List: l}.At(i)))
}
case schema.Type_Which_int32:
for i := 0; i < n; i++ {
val.Index(i).SetInt(int64(capnp.Int32List{List: l}.At(i)))
}
case schema.Type_Which_int64:
for i := 0; i < n; i++ {
val.Index(i).SetInt(capnp.Int64List{List: l}.At(i))
}
case schema.Type_Which_uint8:
for i := 0; i < n; i++ {
val.Index(i).SetUint(uint64(capnp.UInt8List{List: l}.At(i)))
}
case schema.Type_Which_uint16, schema.Type_Which_enum:
for i := 0; i < n; i++ {
val.Index(i).SetUint(uint64(capnp.UInt16List{List: l}.At(i)))
}
case schema.Type_Which_uint32:
for i := 0; i < n; i++ {
val.Index(i).SetUint(uint64(capnp.UInt32List{List: l}.At(i)))
}
case schema.Type_Which_uint64:
for i := 0; i < n; i++ {
val.Index(i).SetUint(capnp.UInt64List{List: l}.At(i))
}
case schema.Type_Which_float32:
for i := 0; i < n; i++ {
val.Index(i).SetFloat(float64(capnp.Float32List{List: l}.At(i)))
}
case schema.Type_Which_float64:
for i := 0; i < n; i++ {
val.Index(i).SetFloat(capnp.Float64List{List: l}.At(i))
}
case schema.Type_Which_text:
if val.Type().Elem().Kind() == reflect.String {
for i := 0; i < n; i++ {
s, err := capnp.TextList{List: l}.At(i)
if err != nil {
// TODO(light): collect errors and finish
return err
}
val.Index(i).SetString(s)
}
} else {
for i := 0; i < n; i++ {
b, err := capnp.TextList{List: l}.BytesAt(i)
if err != nil {
// TODO(light): collect errors and finish
return err
}
val.Index(i).SetBytes(b)
}
}
case schema.Type_Which_data:
for i := 0; i < n; i++ {
b, err := capnp.DataList{List: l}.At(i)
if err != nil {
// TODO(light): collect errors and finish
return err
}
val.Index(i).SetBytes(b)
}
case schema.Type_Which_list:
for i := 0; i < n; i++ {
p, err := capnp.PointerList{List: l}.PtrAt(i)
// TODO(light): collect errors and finish
if err != nil {
return err
}
if err := e.extractList(val.Index(i), elem, p.List()); err != nil {
return err
}
}
case schema.Type_Which_structType:
if val.Type().Elem().Kind() == reflect.Struct {
for i := 0; i < n; i++ {
err := e.extractStruct(val.Index(i), elem.StructType().TypeId(), l.Struct(i))
if err != nil {
return err
}
}
} else {
for i := 0; i < n; i++ {
newval := reflect.New(val.Type().Elem().Elem())
val.Index(i).Set(newval)
err := e.extractStruct(newval, elem.StructType().TypeId(), l.Struct(i))
if err != nil {
return err
}
}
}
default:
return fmt.Errorf("unknown list type %v", elem.Which())
}
return nil
}
var typeMap = map[schema.Type_Which]reflect.Kind{
schema.Type_Which_bool: reflect.Bool,
schema.Type_Which_int8: reflect.Int8,
schema.Type_Which_int16: reflect.Int16,
schema.Type_Which_int32: reflect.Int32,
schema.Type_Which_int64: reflect.Int64,
schema.Type_Which_uint8: reflect.Uint8,
schema.Type_Which_uint16: reflect.Uint16,
schema.Type_Which_uint32: reflect.Uint32,
schema.Type_Which_uint64: reflect.Uint64,
schema.Type_Which_float32: reflect.Float32,
schema.Type_Which_float64: reflect.Float64,
schema.Type_Which_enum: reflect.Uint16,
}
func isTypeMatch(r reflect.Type, s schema.Type) bool {
switch s.Which() {
case schema.Type_Which_text:
return r.Kind() == reflect.String || r.Kind() == reflect.Slice && r.Elem().Kind() == reflect.Uint8
case schema.Type_Which_data:
return r.Kind() == reflect.Slice && r.Elem().Kind() == reflect.Uint8
case schema.Type_Which_structType:
return isStructOrStructPtr(r)
case schema.Type_Which_list:
e, _ := s.List().ElementType()
return r.Kind() == reflect.Slice && isTypeMatch(r.Elem(), e)
}
k, ok := typeMap[s.Which()]
return ok && k == r.Kind()
}