initial commit

1 files changed, 156 insertions, 0 deletions

diff --git a/pkg/binstruct/l2.go b/pkg/binstruct/l2.go
new file mode 100644
index 0000000..005d686
--- /dev/null
+++ b/pkg/binstruct/l2.go
@@ -0,0 +1,156 @@
+package binstruct
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+type End struct{}
+
+type structHandler struct {
+	typ    reflect.Type
+	fields []structField
+	size   int64
+}
+
+type structField struct {
+	tag
+	handler
+	name string
+}
+
+func (sh structHandler) Unmarshal(dat []byte) interface{} {
+	val := reflect.Zero(sh.typ)
+	for i, field := range sh.fields {
+		if field.skip {
+			continue
+		}
+		val.Field(i).Set(reflect.ValueOf(field.Unmarshal(dat[field.off:])))
+	}
+	return val.Interface()
+}
+func (sh structHandler) Marshal(_val interface{}) []byte {
+	val := reflect.ValueOf(_val)
+	ret := make([]byte, 0, sh.size)
+	for i, field := range sh.fields {
+		if field.skip {
+			continue
+		}
+		if int64(len(ret)) != field.off {
+			panic(fmt.Errorf("field %d %q: len(ret)=0x%x but field.off=0x%x", i, field.name, len(ret), field.off))
+		}
+		ret = append(ret, field.Marshal(val.Field(i).Interface())...)
+	}
+	return ret
+}
+func (sh structHandler) Size() int64 {
+	return sh.size
+}
+
+var _ handler = structHandler{}
+
+func genStructHandler(structInfo reflect.Type) (handler, error) {
+	ret := structHandler{
+		typ: structInfo,
+	}
+
+	var curOffset, endOffset int64
+	for i := 0; i < structInfo.NumField(); i++ {
+		var fieldInfo reflect.StructField = structInfo.Field(i)
+
+		fieldTag, err := parseStructTag(fieldInfo.Tag.Get("bin"))
+		if err != nil {
+			return nil, fmt.Errorf("%v: field %q: %w",
+				structInfo, fieldInfo.Name, err)
+		}
+		if fieldTag.skip {
+			ret.fields = append(ret.fields, structField{
+				tag:  fieldTag,
+				name: fieldInfo.Name,
+			})
+			continue
+		}
+
+		if fieldTag.off != curOffset {
+			err := fmt.Errorf("tag says off=0x%x but curOffset=0x%x", fieldTag.off, curOffset)
+			return nil, fmt.Errorf("%v: field %q: %w",
+				structInfo, fieldInfo.Name, err)
+		}
+		if fieldInfo.Type == reflect.TypeOf(End{}) {
+			endOffset = curOffset
+		}
+
+		fieldHandler, err := getHandler(fieldInfo.Type)
+		if err != nil {
+			return nil, fmt.Errorf("%v: field %q: %w",
+				structInfo, fieldInfo.Name, err)
+		}
+
+		if fieldTag.siz != fieldHandler.Size() {
+			err := fmt.Errorf("tag says siz=0x%x but handler.Size()=0x%x", fieldTag.siz, fieldHandler.Size())
+			return nil, fmt.Errorf("%v: field %q: %w",
+				structInfo, fieldInfo.Name, err)
+		}
+		curOffset += fieldTag.siz
+
+		ret.fields = append(ret.fields, structField{
+			tag:     fieldTag,
+			handler: fieldHandler,
+			name:    fieldInfo.Name,
+		})
+	}
+	ret.size = curOffset
+
+	if ret.size != endOffset {
+		return nil, fmt.Errorf("%v: .size=%v but endOffset=%v",
+			structInfo, ret.size, endOffset)
+	}
+
+	return ret, nil
+}
+
+type tag struct {
+	skip bool
+
+	off  int64
+	siz  int64
+	desc string
+}
+
+func parseStructTag(str string) (tag, error) {
+	var ret tag
+	for _, part := range strings.Split(str, ",") {
+		part = strings.TrimSpace(part)
+		if part == "" {
+			continue
+		}
+		if part == "-" {
+			return tag{skip: true}, nil
+		}
+		keyval := strings.SplitN(part, "=", 2)
+		if len(keyval) != 2 {
+			return tag{}, fmt.Errorf("option is not a key=value pair: %q", part)
+		}
+		key := keyval[0]
+		val := keyval[1]
+		switch key {
+		case "off":
+			vint, err := strconv.ParseInt(val, 16, 64)
+			if err != nil {
+				return tag{}, err
+			}
+			ret.off = vint
+		case "siz":
+			vint, err := strconv.ParseInt(val, 16, 64)
+			if err != nil {
+				return tag{}, err
+			}
+			ret.siz = vint
+		case "desc":
+			ret.desc = val
+		}
+	}
+	return ret, nil
+}