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package objectpacker
import (
"bytes"
"encoding/binary"
"fmt"
"github.com/pkg/errors"
"io"
"io/ioutil"
"reflect"
"sort"
)
// MustPackSlice calls PackAny using items and panics if there was an error.
func MustPackSlice(items ...interface{}) []byte {
var buf bytes.Buffer
if err := PackAny(items, &buf); err != nil {
panic(err)
}
return buf.Bytes()
}
// PackAny packs any JSON-encodable value (ex. structs, also ignores interfaces like encoding.TextMarshaler)
// to a BSON-similar format suitable for consistent hashing. Spec:
//
// PackAny(nil) => 0x0
// PackAny(false) => 0x1
// PackAny(true) => 0x2
// PackAny(float64(42)) => 0x3 ieee754_binary64_bigendian(42)
// PackAny("exämple") => 0x4 uint64_bigendian(len([]byte("exämple"))) []byte("exämple")
// PackAny([]uint8{0x42}) => 0x4 uint64_bigendian(len([]uint8{0x42})) []uint8{0x42}
// PackAny([1]uint8{0x42}) => 0x4 uint64_bigendian(len([1]uint8{0x42})) [1]uint8{0x42}
// PackAny([]T{x,y}) => 0x5 uint64_bigendian(len([]T{x,y})) PackAny(x) PackAny(y)
// PackAny(map[K]V{x:y}) => 0x6 uint64_bigendian(len(map[K]V{x:y})) len(map_key(x)) map_key(x) PackAny(y)
// PackAny((*T)(nil)) => 0x0
// PackAny((*T)(0x42)) => PackAny(*(*T)(0x42))
// PackAny(x) => panic()
//
// map_key([1]uint8{0x42}) => [1]uint8{0x42}
// map_key(x) => []byte(fmt.Sprint(x))
func PackAny(in interface{}, out io.Writer) error {
return errors.Wrapf(packValue(reflect.ValueOf(in), out), "can't pack %#v", in)
}
var tByte = reflect.TypeOf(byte(0))
var tBytes = reflect.TypeOf([]uint8(nil))
// packValue does the actual job of packAny and just exists for recursion w/o unnecessary reflect.ValueOf calls.
func packValue(in reflect.Value, out io.Writer) error {
switch kind := in.Kind(); kind {
case reflect.Invalid: // nil
_, err := out.Write([]byte{0})
return err
case reflect.Bool:
if in.Bool() {
_, err := out.Write([]byte{2})
return err
} else {
_, err := out.Write([]byte{1})
return err
}
case reflect.Float64:
if _, err := out.Write([]byte{3}); err != nil {
return err
}
return binary.Write(out, binary.BigEndian, in.Float())
case reflect.Array, reflect.Slice:
if typ := in.Type(); typ.Elem() == tByte {
if kind == reflect.Array {
if !in.CanAddr() {
vNewElem := reflect.New(typ).Elem()
vNewElem.Set(in)
in = vNewElem
}
in = in.Slice(0, in.Len())
}
// Pack []byte as string, not array of numbers.
return packString(in.Convert(tBytes). // Support types.Binary
Interface().([]uint8), out)
}
if _, err := out.Write([]byte{5}); err != nil {
return err
}
l := in.Len()
if err := binary.Write(out, binary.BigEndian, uint64(l)); err != nil {
return err
}
for i := 0; i < l; i++ {
if err := packValue(in.Index(i), out); err != nil {
return err
}
}
// If there aren't any values to pack, ...
if l < 1 {
// ... create one and pack it - panics on disallowed type.
_ = packValue(reflect.Zero(in.Type().Elem()), ioutil.Discard)
}
return nil
case reflect.Interface:
return packValue(in.Elem(), out)
case reflect.Map:
type kv struct {
key []byte
value reflect.Value
}
if _, err := out.Write([]byte{6}); err != nil {
return err
}
l := in.Len()
if err := binary.Write(out, binary.BigEndian, uint64(l)); err != nil {
return err
}
sorted := make([]kv, 0, l)
{
iter := in.MapRange()
for iter.Next() {
var packedKey []byte
if key := iter.Key(); key.Kind() == reflect.Array {
if typ := key.Type(); typ.Elem() == tByte {
if !key.CanAddr() {
vNewElem := reflect.New(typ).Elem()
vNewElem.Set(key)
key = vNewElem
}
packedKey = key.Slice(0, key.Len()).Interface().([]byte)
} else {
// Not just stringify the key (below), but also pack it (here) - panics on disallowed type.
_ = packValue(iter.Key(), ioutil.Discard)
packedKey = []byte(fmt.Sprint(key.Interface()))
}
} else {
// Not just stringify the key (below), but also pack it (here) - panics on disallowed type.
_ = packValue(iter.Key(), ioutil.Discard)
packedKey = []byte(fmt.Sprint(key.Interface()))
}
sorted = append(sorted, kv{packedKey, iter.Value()})
}
}
sort.Slice(sorted, func(i, j int) bool { return bytes.Compare(sorted[i].key, sorted[j].key) < 0 })
for _, kv := range sorted {
if err := binary.Write(out, binary.BigEndian, uint64(len(kv.key))); err != nil {
return err
}
if _, err := out.Write(kv.key); err != nil {
return err
}
if err := packValue(kv.value, out); err != nil {
return err
}
}
// If there aren't any key-value pairs to pack, ...
if l < 1 {
typ := in.Type()
// ... create one and pack it - panics on disallowed type.
_ = packValue(reflect.Zero(typ.Key()), ioutil.Discard)
_ = packValue(reflect.Zero(typ.Elem()), ioutil.Discard)
}
return nil
case reflect.Ptr:
if in.IsNil() {
err := packValue(reflect.Value{}, out)
// Create a fictive referenced value and pack it - panics on disallowed type.
_ = packValue(reflect.Zero(in.Type().Elem()), ioutil.Discard)
return err
} else {
return packValue(in.Elem(), out)
}
case reflect.String:
return packString([]byte(in.String()), out)
default:
panic("bad type: " + in.Kind().String())
}
}
// packString deduplicates string packing of multiple locations in packValue.
func packString(in []byte, out io.Writer) error {
if _, err := out.Write([]byte{4}); err != nil {
return err
}
if err := binary.Write(out, binary.BigEndian, uint64(len(in))); err != nil {
return err
}
_, err := out.Write(in)
return err
}
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