deploy: 06a1bdf735

vendor/gopl.io/ch12/sexpr/encode.go

@@ -0,0 +1,97 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 339.
+
+package sexpr
+
+import (
+	"bytes"
+	"fmt"
+	"reflect"
+)
+
+//!+Marshal
+// Marshal encodes a Go value in S-expression form.
+func Marshal(v interface{}) ([]byte, error) {
+	var buf bytes.Buffer
+	if err := encode(&buf, reflect.ValueOf(v)); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+//!-Marshal
+
+// encode writes to buf an S-expression representation of v.
+//!+encode
+func encode(buf *bytes.Buffer, v reflect.Value) error {
+	switch v.Kind() {
+	case reflect.Invalid:
+		buf.WriteString("nil")
+
+	case reflect.Int, reflect.Int8, reflect.Int16,
+		reflect.Int32, reflect.Int64:
+		fmt.Fprintf(buf, "%d", v.Int())
+
+	case reflect.Uint, reflect.Uint8, reflect.Uint16,
+		reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		fmt.Fprintf(buf, "%d", v.Uint())
+
+	case reflect.String:
+		fmt.Fprintf(buf, "%q", v.String())
+
+	case reflect.Ptr:
+		return encode(buf, v.Elem())
+
+	case reflect.Array, reflect.Slice: // (value ...)
+		buf.WriteByte('(')
+		for i := 0; i < v.Len(); i++ {
+			if i > 0 {
+				buf.WriteByte(' ')
+			}
+			if err := encode(buf, v.Index(i)); err != nil {
+				return err
+			}
+		}
+		buf.WriteByte(')')
+
+	case reflect.Struct: // ((name value) ...)
+		buf.WriteByte('(')
+		for i := 0; i < v.NumField(); i++ {
+			if i > 0 {
+				buf.WriteByte(' ')
+			}
+			fmt.Fprintf(buf, "(%s ", v.Type().Field(i).Name)
+			if err := encode(buf, v.Field(i)); err != nil {
+				return err
+			}
+			buf.WriteByte(')')
+		}
+		buf.WriteByte(')')
+
+	case reflect.Map: // ((key value) ...)
+		buf.WriteByte('(')
+		for i, key := range v.MapKeys() {
+			if i > 0 {
+				buf.WriteByte(' ')
+			}
+			buf.WriteByte('(')
+			if err := encode(buf, key); err != nil {
+				return err
+			}
+			buf.WriteByte(' ')
+			if err := encode(buf, v.MapIndex(key)); err != nil {
+				return err
+			}
+			buf.WriteByte(')')
+		}
+		buf.WriteByte(')')
+
+	default: // float, complex, bool, chan, func, interface
+		return fmt.Errorf("unsupported type: %s", v.Type())
+	}
+	return nil
+}
+
+//!-encode