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package binstruct
import (
"encoding/binary"
"fmt"
"reflect"
)
type handler interface {
Unmarshal(dat []byte) interface{}
Marshal(val interface{}) []byte
Size() int64
}
type primitive struct {
unmarshal func(dat []byte) interface{}
marshal func(val interface{}) []byte
size int64
}
func (p primitive) Unmarshal(dat []byte) interface{} { return p.unmarshal(dat) }
func (p primitive) Marshal(val interface{}) []byte { return p.marshal(val) }
func (p primitive) Size() int64 { return p.size }
var _ handler = primitive{}
func genHandler(typ reflect.Type) (handler, error) {
switch typ.Kind() {
case reflect.Invalid: // invalid
return nil, fmt.Errorf("unsupported kind: %s: %v", typ.Kind(), typ)
case reflect.Bool, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128: // I don't wanna
return nil, fmt.Errorf("unsupported kind: %s: %v", typ.Kind(), typ)
case reflect.Int, reflect.Uint, reflect.Uintptr: // platform specific
return nil, fmt.Errorf("unsupported kind: %s: %v", typ.Kind(), typ)
case reflect.Chan, reflect.Func, reflect.Interface, reflect.UnsafePointer: // runtime
return nil, fmt.Errorf("unsupported kind: %s: %v", typ.Kind(), typ)
case reflect.Map, reflect.Slice, reflect.String: // dynamic size
return nil, fmt.Errorf("unsupported kind: %s: %v", typ.Kind(), typ)
// uint ////////////////////////////////////////////////////////////////
case reflect.Uint8:
return primitive{
unmarshal: func(dat []byte) interface{} { return dat[0] },
marshal: func(val interface{}) []byte { return []byte{val.(uint8)} },
size: 1,
}, nil
case reflect.Uint16:
return primitive{
unmarshal: func(dat []byte) interface{} { return binary.LittleEndian.Uint16(dat) },
marshal: func(val interface{}) []byte {
var buf [2]byte
binary.LittleEndian.PutUint16(buf[:], val.(uint16))
return buf[:]
},
size: 2,
}, nil
case reflect.Uint32:
return primitive{
unmarshal: func(dat []byte) interface{} { return binary.LittleEndian.Uint32(dat) },
marshal: func(val interface{}) []byte {
var buf [4]byte
binary.LittleEndian.PutUint32(buf[:], val.(uint32))
return buf[:]
},
size: 4,
}, nil
case reflect.Uint64:
return primitive{
unmarshal: func(dat []byte) interface{} { return binary.LittleEndian.Uint64(dat) },
marshal: func(val interface{}) []byte {
var buf [8]byte
binary.LittleEndian.PutUint64(buf[:], val.(uint64))
return buf[:]
},
size: 8,
}, nil
// int /////////////////////////////////////////////////////////////////
case reflect.Int8:
return primitive{
unmarshal: func(dat []byte) interface{} { return int8(dat[0]) },
marshal: func(val interface{}) []byte { return []byte{uint8(val.(int8))} },
size: 1,
}, nil
case reflect.Int16:
return primitive{
unmarshal: func(dat []byte) interface{} { return int16(binary.LittleEndian.Uint16(dat)) },
marshal: func(val interface{}) []byte {
var buf [2]byte
binary.LittleEndian.PutUint16(buf[:], uint16(val.(int16)))
return buf[:]
},
size: 2,
}, nil
case reflect.Int32:
return primitive{
unmarshal: func(dat []byte) interface{} { return int32(binary.LittleEndian.Uint32(dat)) },
marshal: func(val interface{}) []byte {
var buf [4]byte
binary.LittleEndian.PutUint32(buf[:], uint32(val.(int32)))
return buf[:]
},
size: 4,
}, nil
case reflect.Int64:
return primitive{
unmarshal: func(dat []byte) interface{} { return int64(binary.LittleEndian.Uint64(dat)) },
marshal: func(val interface{}) []byte {
var buf [8]byte
binary.LittleEndian.PutUint64(buf[:], uint64(val.(int64)))
return buf[:]
},
size: 8,
}, nil
// composite ///////////////////////////////////////////////////////////
case reflect.Ptr:
inner, err := getHandler(typ.Elem())
if err != nil {
return nil, fmt.Errorf("%v: %w", typ, err)
}
return primitive{
unmarshal: func(dat []byte) interface{} {
return reflect.ValueOf(inner.Unmarshal(dat)).Addr().Interface()
},
marshal: func(val interface{}) []byte {
return inner.Marshal(reflect.ValueOf(val).Elem().Interface())
},
size: inner.Size(),
}, nil
case reflect.Array:
inner, err := getHandler(typ.Elem())
if err != nil {
return nil, fmt.Errorf("%v: %w", typ, err)
}
return primitive{
unmarshal: func(dat []byte) interface{} {
val := reflect.Zero(typ)
for i := 0; i < typ.Len(); i++ {
fmt.Printf("%v[%d]: %v\n", typ, i, val.Index(i))
val.Index(i).Set(reflect.ValueOf(inner.Unmarshal(dat[i*int(inner.Size()):])))
}
return val.Interface()
},
marshal: func(val interface{}) []byte {
_val := reflect.ValueOf(val)
var ret []byte
for i := 0; i < typ.Len(); i++ {
ret = append(ret, inner.Marshal(_val.Index(i).Interface())...)
}
return ret
},
size: inner.Size() * int64(typ.Len()),
}, nil
case reflect.Struct:
return genStructHandler(typ)
// end /////////////////////////////////////////////////////////////////
default:
panic(fmt.Errorf("unknown kind: %v: %v", typ.Kind(), typ))
}
}
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