Implemented "php" tags for structs (#20)

If you marshal or unmarshal from/into a struct, you may want to use go tags for it, instead of staticly using the struct field names just changing the first letter to upper/lower case.

Example:

    type Target struct {
        FirstName string `php:"vorname"`
        LastName string  `php:"nachname"`
    }

This will correctly be filled with the according fields of serialized php object.
Also unmarshaling will not fail if a struct field does not exist, because you may want to skip some fields from php objects.

consume.go

@@ -2,7 +2,6 @@ package phpserialize
 
 import (
 	"errors"
-	"fmt"
 	"reflect"
 	"strconv"
 )
@@ -170,19 +169,9 @@ func consumeObjectAsMap(data []byte, offset int) (
 	return result, offset + 1, nil
 }
 
-func setField(obj interface{}, name string, value interface{}) error {
-	structValue := reflect.ValueOf(obj).Elem()
-
-	// We need to uppercase the first letter for compatibility.
-	// The Marshal() function does the opposite of this.
-	structFieldValue := structValue.FieldByName(upperCaseFirstLetter(name))
-
+func setField(structFieldValue reflect.Value, value interface{}) error {
 	if !structFieldValue.IsValid() {
-		return fmt.Errorf("no such field: %s in obj", name)
-	}
-
-	if !structFieldValue.CanSet() {
-		return fmt.Errorf("cannot set %s field value", name)
+		return nil
 	}
 
 	val := reflect.ValueOf(value)
@@ -198,7 +187,7 @@ func setField(obj interface{}, name string, value interface{}) error {
 
 	case reflect.Struct:
 		m := val.Interface().(map[interface{}]interface{})
-		fillStruct(structFieldValue.Addr().Interface(), m)
+		fillStruct(structFieldValue, m)
 
 	default:
 		structFieldValue.Set(val)
@@ -208,18 +197,30 @@ func setField(obj interface{}, name string, value interface{}) error {
 }
 
 // https://stackoverflow.com/questions/26744873/converting-map-to-struct
-func fillStruct(obj interface{}, m map[interface{}]interface{}) error {
-	for k, v := range m {
-		err := setField(obj, k.(string), v)
-		if err != nil {
-			return err
+func fillStruct(obj reflect.Value, m map[interface{}]interface{}) error {
+	tt := obj.Type()
+	for i := 0; i < obj.NumField(); i++ {
+		field := obj.Field(i)
+		if !field.CanSet() {
+			continue
+		}
+		var key string
+		if tag := tt.Field(i).Tag.Get("php"); tag == "-" {
+			continue
+		} else if tag != "" {
+			key = tag
+		} else {
+			key = lowerCaseFirstLetter(tt.Field(i).Name)
+		}
+		if v, ok := m[key]; ok {
+			setField(field, v)
 		}
 	}
 
 	return nil
 }
 
-func consumeObject(data []byte, offset int, v interface{}) (int, error) {
+func consumeObject(data []byte, offset int, v reflect.Value) (int, error) {
 	if !checkType(data, 'O', offset) {
 		return -1, errors.New("not an object")
 	}

example/test.go

@@ -1,8 +1,8 @@
 package main
 
 import (
-	"github.com/elliotchance/phpserialize"
 	"fmt"
+	"github.com/elliotchance/phpserialize"
 )
 
 func main() {

serialize.go

@@ -165,7 +165,12 @@ func MarshalStruct(input interface{}, options *MarshalOptions) ([]byte, error) {
 		// with an uppercase letter) we must change it to lower case. If
 		// you really do want it to be upper case you will have to wait
 		// for when tags are supported on individual fields.
-		fieldName := lowerCaseFirstLetter(typeOfValue.Field(i).Name)
+		fieldName := typeOfValue.Field(i).Tag.Get("php")
+		if fieldName == "-" {
+			continue
+		} else if fieldName == "" {
+			fieldName = lowerCaseFirstLetter(typeOfValue.Field(i).Name)
+		}
 		buffer.Write(MarshalString(fieldName))
 
 		m, err := Marshal(f.Interface(), options)
@@ -188,11 +193,11 @@ func MarshalStruct(input interface{}, options *MarshalOptions) ([]byte, error) {
 // Marshal is the canonical way to perform the equivalent of serialize() in PHP.
 // It can handle encoding scalar types, slices and maps.
 func Marshal(input interface{}, options *MarshalOptions) ([]byte, error) {
-	
+
 	if options == nil {
 		options = DefaultMarshalOptions()
 	}
-	
+
 	// []byte is a special case because all strings (binary and otherwise)
 	// are handled as strings in PHP.
 	if bytesToEncode, ok := input.([]byte); ok {

serialize_test.go

@@ -13,6 +13,14 @@ type struct1 struct {
 	Baz    string
 }
 
+type structTag struct {
+	Foo     Struct2 `php:"bar"`
+	Bar     int     `php:"foo"`
+	hidden  bool
+	Balu    string `php:"baz"`
+	Ignored string `php:"-"`
+}
+
 type Struct2 struct {
 	Qux float64
 }
@@ -125,6 +133,13 @@ var marshalTests = map[string]marshalTest{
 		nil,
 	},
 
+	// encode object (struct with tags)
+	"structTag{Bar int, Foo Struct2{Qux float64}, hidden bool, Balu string}": {
+		structTag{Struct2{1.23}, 10, true, "yay", ""},
+		[]byte("O:9:\"structTag\":4:{s:3:\"bar\";O:7:\"Struct2\":1:{s:3:\"qux\";d:1.23;}s:3:\"foo\";i:10;s:3:\"baz\";s:3:\"yay\";}"),
+		nil,
+	},
+
 	// stdClassOnly
 	"struct1{Foo int, Bar Struct2{Qux float64}, hidden bool}: OnlyStdClass = true": {
 		struct1{10, Struct2{1.23}, true, "yay"},

unserialize.go

@@ -113,7 +113,7 @@ func UnmarshalAssociativeArray(data []byte) (map[interface{}]interface{}, error)
 	return result, err
 }
 
-func UnmarshalObject(data []byte, v interface{}) error {
+func UnmarshalObject(data []byte, v reflect.Value) error {
 	_, err := consumeObject(data, 0, v)
 	return err
 }
@@ -122,8 +122,7 @@ func Unmarshal(data []byte, v interface{}) error {
 	value := reflect.ValueOf(v).Elem()
 
 	switch value.Kind() {
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32,
-		reflect.Int64:
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 		v, err := UnmarshalInt(data)
 		if err != nil {
 			return err
@@ -195,7 +194,7 @@ func Unmarshal(data []byte, v interface{}) error {
 		return nil
 
 	case reflect.Struct:
-		err := UnmarshalObject(data, v)
+		err := UnmarshalObject(data, value)
 		if err != nil {
 			return err
 		}

unserialize_test.go

@@ -499,6 +499,29 @@ func TestUnmarshalObject(t *testing.T) {
 	}
 }
 
+func TestUnmarshalObjectWithTags(t *testing.T) {
+	data := "O:7:\"struct1\":3:{s:3:\"foo\";i:10;s:3:\"bar\";O:7:\"Struct2\":1:{s:3:\"qux\";d:1.23;}s:3:\"baz\";s:3:\"yay\";}"
+	var result structTag
+	err := phpserialize.Unmarshal([]byte(data), &result)
+	expectErrorToNotHaveOccurred(t, err)
+
+	if result.Bar != 10 {
+		t.Errorf("Expected %v, got %v", 10, result.Bar)
+	}
+
+	if result.Foo.Qux != 1.23 {
+		t.Errorf("Expected %v, got %v", 1.23, result.Foo.Qux)
+	}
+
+	if result.Balu != "yay" {
+		t.Errorf("Expected %v, got %v", "yay", result.Balu)
+	}
+
+	if result.Ignored != "" {
+		t.Errorf("Expected %v, got %v", "yay", result.Ignored)
+	}
+}
+
 func TestUnmarshalObjectIntoMap(t *testing.T) {
 	data := "O:7:\"struct1\":3:{s:3:\"foo\";i:10;s:3:\"bar\";O:7:\"Struct2\":1:{s:3:\"qux\";d:1.23;}s:3:\"baz\";s:3:\"yay\";}"
 	var result map[interface{}]interface{}

util_test.go

@@ -1,9 +1,9 @@
 package phpserialize_test
 
 import (
-	"testing"
 	"github.com/elliotchance/phpserialize"
 	"reflect"
+	"testing"
 )
 
 func TestStringifyKeysOnEmptyMap(t *testing.T) {