internal/impl: initial commit

This provides an implementation of the has, get, set, clear methods for each
field in a message. The approach taken here is similar to the table-driven
implementation in the current v1 proto package.

The pointer_reflect.go and pointer_unsafe.go files are a simplified version of
the same files in the v1 implementation. They provide a pointer abstraction
that enables a high-efficiency approach in a non-purego environment.
The unsafe fast-path is not implemented in this commit.

This commit only implements the accessor methods for scalars using pure
Go reflection.

Change-Id: Icdf707e9d4e3385e55434f93b30a341a7680ae11
Reviewed-on: https://go-review.googlesource.com/135136
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/internal/impl/message_test.go b/internal/impl/message_test.go
new file mode 100644
index 0000000..f9d674a
--- /dev/null
+++ b/internal/impl/message_test.go
@@ -0,0 +1,292 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package impl
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+
+	pref "google.golang.org/proto/reflect/protoreflect"
+	ptype "google.golang.org/proto/reflect/prototype"
+)
+
+type (
+	MyBool    bool
+	MyInt32   int32
+	MyInt64   int64
+	MyUint32  uint32
+	MyUint64  uint64
+	MyFloat32 float32
+	MyFloat64 float64
+	MyString  string
+	MyBytes   []byte
+)
+
+type ScalarProto2 struct {
+	Bool    *bool    `protobuf:"1"`
+	Int32   *int32   `protobuf:"2"`
+	Int64   *int64   `protobuf:"3"`
+	Uint32  *uint32  `protobuf:"4"`
+	Uint64  *uint64  `protobuf:"5"`
+	Float32 *float32 `protobuf:"6"`
+	Float64 *float64 `protobuf:"7"`
+	String  *string  `protobuf:"8"`
+	StringA []byte   `protobuf:"9"`
+	Bytes   []byte   `protobuf:"10"`
+	BytesA  *string  `protobuf:"11"`
+
+	MyBool    *MyBool    `protobuf:"12"`
+	MyInt32   *MyInt32   `protobuf:"13"`
+	MyInt64   *MyInt64   `protobuf:"14"`
+	MyUint32  *MyUint32  `protobuf:"15"`
+	MyUint64  *MyUint64  `protobuf:"16"`
+	MyFloat32 *MyFloat32 `protobuf:"17"`
+	MyFloat64 *MyFloat64 `protobuf:"18"`
+	MyString  *MyString  `protobuf:"19"`
+	MyStringA MyBytes    `protobuf:"20"`
+	MyBytes   MyBytes    `protobuf:"21"`
+	MyBytesA  *MyString  `protobuf:"22"`
+}
+
+type ScalarProto3 struct {
+	Bool    bool    `protobuf:"1"`
+	Int32   int32   `protobuf:"2"`
+	Int64   int64   `protobuf:"3"`
+	Uint32  uint32  `protobuf:"4"`
+	Uint64  uint64  `protobuf:"5"`
+	Float32 float32 `protobuf:"6"`
+	Float64 float64 `protobuf:"7"`
+	String  string  `protobuf:"8"`
+	StringA []byte  `protobuf:"9"`
+	Bytes   []byte  `protobuf:"10"`
+	BytesA  string  `protobuf:"11"`
+
+	MyBool    MyBool    `protobuf:"12"`
+	MyInt32   MyInt32   `protobuf:"13"`
+	MyInt64   MyInt64   `protobuf:"14"`
+	MyUint32  MyUint32  `protobuf:"15"`
+	MyUint64  MyUint64  `protobuf:"16"`
+	MyFloat32 MyFloat32 `protobuf:"17"`
+	MyFloat64 MyFloat64 `protobuf:"18"`
+	MyString  MyString  `protobuf:"19"`
+	MyStringA MyBytes   `protobuf:"20"`
+	MyBytes   MyBytes   `protobuf:"21"`
+	MyBytesA  MyString  `protobuf:"22"`
+}
+
+func TestFieldFuncs(t *testing.T) {
+	V := pref.ValueOf
+	type (
+		// has checks that each field matches the list.
+		hasOp []bool
+		// get checks that each field returns values matching the list.
+		getOp []pref.Value
+		// set calls set on each field with the given value in the list.
+		setOp []pref.Value
+		// clear calls clear on each field.
+		clearOp []bool
+		// equal checks that the current message equals the provided value.
+		equalOp struct{ want interface{} }
+
+		testOp interface{} // has | get | set | clear | equal
+	)
+
+	tests := []struct {
+		structType  reflect.Type
+		messageDesc ptype.StandaloneMessage
+		testOps     []testOp
+	}{{
+		structType: reflect.TypeOf(ScalarProto2{}),
+		messageDesc: ptype.StandaloneMessage{
+			Syntax:   pref.Proto2,
+			FullName: "ScalarProto2",
+			Fields: []ptype.Field{
+				{Name: "f1", Number: 1, Cardinality: pref.Optional, Kind: pref.BoolKind, Default: V(bool(true))},
+				{Name: "f2", Number: 2, Cardinality: pref.Optional, Kind: pref.Int32Kind, Default: V(int32(2))},
+				{Name: "f3", Number: 3, Cardinality: pref.Optional, Kind: pref.Int64Kind, Default: V(int64(3))},
+				{Name: "f4", Number: 4, Cardinality: pref.Optional, Kind: pref.Uint32Kind, Default: V(uint32(4))},
+				{Name: "f5", Number: 5, Cardinality: pref.Optional, Kind: pref.Uint64Kind, Default: V(uint64(5))},
+				{Name: "f6", Number: 6, Cardinality: pref.Optional, Kind: pref.FloatKind, Default: V(float32(6))},
+				{Name: "f7", Number: 7, Cardinality: pref.Optional, Kind: pref.DoubleKind, Default: V(float64(7))},
+				{Name: "f8", Number: 8, Cardinality: pref.Optional, Kind: pref.StringKind, Default: V(string("8"))},
+				{Name: "f9", Number: 9, Cardinality: pref.Optional, Kind: pref.StringKind, Default: V(string("9"))},
+				{Name: "f10", Number: 10, Cardinality: pref.Optional, Kind: pref.BytesKind, Default: V([]byte("10"))},
+				{Name: "f11", Number: 11, Cardinality: pref.Optional, Kind: pref.BytesKind, Default: V([]byte("11"))},
+
+				{Name: "f12", Number: 12, Cardinality: pref.Optional, Kind: pref.BoolKind, Default: V(bool(true))},
+				{Name: "f13", Number: 13, Cardinality: pref.Optional, Kind: pref.Int32Kind, Default: V(int32(13))},
+				{Name: "f14", Number: 14, Cardinality: pref.Optional, Kind: pref.Int64Kind, Default: V(int64(14))},
+				{Name: "f15", Number: 15, Cardinality: pref.Optional, Kind: pref.Uint32Kind, Default: V(uint32(15))},
+				{Name: "f16", Number: 16, Cardinality: pref.Optional, Kind: pref.Uint64Kind, Default: V(uint64(16))},
+				{Name: "f17", Number: 17, Cardinality: pref.Optional, Kind: pref.FloatKind, Default: V(float32(17))},
+				{Name: "f18", Number: 18, Cardinality: pref.Optional, Kind: pref.DoubleKind, Default: V(float64(18))},
+				{Name: "f19", Number: 19, Cardinality: pref.Optional, Kind: pref.StringKind, Default: V(string("19"))},
+				{Name: "f20", Number: 20, Cardinality: pref.Optional, Kind: pref.StringKind, Default: V(string("20"))},
+				{Name: "f21", Number: 21, Cardinality: pref.Optional, Kind: pref.BytesKind, Default: V([]byte("21"))},
+				{Name: "f22", Number: 22, Cardinality: pref.Optional, Kind: pref.BytesKind, Default: V([]byte("22"))},
+			},
+		},
+		testOps: []testOp{
+			hasOp([]bool{
+				false, false, false, false, false, false, false, false, false, false, false,
+				false, false, false, false, false, false, false, false, false, false, false,
+			}),
+			getOp([]pref.Value{
+				V(bool(true)), V(int32(2)), V(int64(3)), V(uint32(4)), V(uint64(5)), V(float32(6)), V(float64(7)), V(string("8")), V(string("9")), V([]byte("10")), V([]byte("11")),
+				V(bool(true)), V(int32(13)), V(int64(14)), V(uint32(15)), V(uint64(16)), V(float32(17)), V(float64(18)), V(string("19")), V(string("20")), V([]byte("21")), V([]byte("22")),
+			}),
+			setOp([]pref.Value{
+				V(bool(false)), V(int32(0)), V(int64(0)), V(uint32(0)), V(uint64(0)), V(float32(0)), V(float64(0)), V(string("")), V(string("")), V([]byte(nil)), V([]byte(nil)),
+				V(bool(false)), V(int32(0)), V(int64(0)), V(uint32(0)), V(uint64(0)), V(float32(0)), V(float64(0)), V(string("")), V(string("")), V([]byte(nil)), V([]byte(nil)),
+			}),
+			hasOp([]bool{
+				true, true, true, true, true, true, true, true, true, true, true,
+				true, true, true, true, true, true, true, true, true, true, true,
+			}),
+			equalOp{&ScalarProto2{
+				new(bool), new(int32), new(int64), new(uint32), new(uint64), new(float32), new(float64), new(string), []byte{}, []byte{}, new(string),
+				new(MyBool), new(MyInt32), new(MyInt64), new(MyUint32), new(MyUint64), new(MyFloat32), new(MyFloat64), new(MyString), MyBytes{}, MyBytes{}, new(MyString),
+			}},
+			clearOp([]bool{
+				true, true, true, true, true, true, true, true, true, true, true,
+				true, true, true, true, true, true, true, true, true, true, true,
+			}),
+			equalOp{&ScalarProto2{}},
+		},
+	}, {
+		structType: reflect.TypeOf(ScalarProto3{}),
+		messageDesc: ptype.StandaloneMessage{
+			Syntax:   pref.Proto3,
+			FullName: "ScalarProto3",
+			Fields: []ptype.Field{
+				{Name: "f1", Number: 1, Cardinality: pref.Optional, Kind: pref.BoolKind},
+				{Name: "f2", Number: 2, Cardinality: pref.Optional, Kind: pref.Int32Kind},
+				{Name: "f3", Number: 3, Cardinality: pref.Optional, Kind: pref.Int64Kind},
+				{Name: "f4", Number: 4, Cardinality: pref.Optional, Kind: pref.Uint32Kind},
+				{Name: "f5", Number: 5, Cardinality: pref.Optional, Kind: pref.Uint64Kind},
+				{Name: "f6", Number: 6, Cardinality: pref.Optional, Kind: pref.FloatKind},
+				{Name: "f7", Number: 7, Cardinality: pref.Optional, Kind: pref.DoubleKind},
+				{Name: "f8", Number: 8, Cardinality: pref.Optional, Kind: pref.StringKind},
+				{Name: "f9", Number: 9, Cardinality: pref.Optional, Kind: pref.StringKind},
+				{Name: "f10", Number: 10, Cardinality: pref.Optional, Kind: pref.BytesKind},
+				{Name: "f11", Number: 11, Cardinality: pref.Optional, Kind: pref.BytesKind},
+
+				{Name: "f12", Number: 12, Cardinality: pref.Optional, Kind: pref.BoolKind},
+				{Name: "f13", Number: 13, Cardinality: pref.Optional, Kind: pref.Int32Kind},
+				{Name: "f14", Number: 14, Cardinality: pref.Optional, Kind: pref.Int64Kind},
+				{Name: "f15", Number: 15, Cardinality: pref.Optional, Kind: pref.Uint32Kind},
+				{Name: "f16", Number: 16, Cardinality: pref.Optional, Kind: pref.Uint64Kind},
+				{Name: "f17", Number: 17, Cardinality: pref.Optional, Kind: pref.FloatKind},
+				{Name: "f18", Number: 18, Cardinality: pref.Optional, Kind: pref.DoubleKind},
+				{Name: "f19", Number: 19, Cardinality: pref.Optional, Kind: pref.StringKind},
+				{Name: "f20", Number: 20, Cardinality: pref.Optional, Kind: pref.StringKind},
+				{Name: "f21", Number: 21, Cardinality: pref.Optional, Kind: pref.BytesKind},
+				{Name: "f22", Number: 22, Cardinality: pref.Optional, Kind: pref.BytesKind},
+			},
+		},
+		testOps: []testOp{
+			hasOp([]bool{
+				false, false, false, false, false, false, false, false, false, false, false,
+				false, false, false, false, false, false, false, false, false, false, false,
+			}),
+			getOp([]pref.Value{
+				V(bool(false)), V(int32(0)), V(int64(0)), V(uint32(0)), V(uint64(0)), V(float32(0)), V(float64(0)), V(string("")), V(string("")), V([]byte(nil)), V([]byte(nil)),
+				V(bool(false)), V(int32(0)), V(int64(0)), V(uint32(0)), V(uint64(0)), V(float32(0)), V(float64(0)), V(string("")), V(string("")), V([]byte(nil)), V([]byte(nil)),
+			}),
+			setOp([]pref.Value{
+				V(bool(false)), V(int32(0)), V(int64(0)), V(uint32(0)), V(uint64(0)), V(float32(0)), V(float64(0)), V(string("")), V(string("")), V([]byte(nil)), V([]byte(nil)),
+				V(bool(false)), V(int32(0)), V(int64(0)), V(uint32(0)), V(uint64(0)), V(float32(0)), V(float64(0)), V(string("")), V(string("")), V([]byte(nil)), V([]byte(nil)),
+			}),
+			hasOp([]bool{
+				false, false, false, false, false, false, false, false, false, false, false,
+				false, false, false, false, false, false, false, false, false, false, false,
+			}),
+			equalOp{&ScalarProto3{}},
+			setOp([]pref.Value{
+				V(bool(true)), V(int32(2)), V(int64(3)), V(uint32(4)), V(uint64(5)), V(float32(6)), V(float64(7)), V(string("8")), V(string("9")), V([]byte("10")), V([]byte("11")),
+				V(bool(true)), V(int32(13)), V(int64(14)), V(uint32(15)), V(uint64(16)), V(float32(17)), V(float64(18)), V(string("19")), V(string("20")), V([]byte("21")), V([]byte("22")),
+			}),
+			hasOp([]bool{
+				true, true, true, true, true, true, true, true, true, true, true,
+				true, true, true, true, true, true, true, true, true, true, true,
+			}),
+			equalOp{&ScalarProto3{
+				true, 2, 3, 4, 5, 6, 7, "8", []byte("9"), []byte("10"), "11",
+				true, 13, 14, 15, 16, 17, 18, "19", []byte("20"), []byte("21"), "22",
+			}},
+			clearOp([]bool{
+				true, true, true, true, true, true, true, true, true, true, true,
+				true, true, true, true, true, true, true, true, true, true, true,
+			}),
+			equalOp{&ScalarProto3{}},
+		},
+	}}
+
+	for _, tt := range tests {
+		t.Run(tt.structType.Name(), func(t *testing.T) {
+			// Construct the message descriptor.
+			md, err := ptype.NewMessage(&tt.messageDesc)
+			if err != nil {
+				t.Fatalf("NewMessage error: %v", err)
+			}
+
+			// Generate the field functions from the message descriptor.
+			var mi MessageInfo
+			mi.generateFieldFuncs(tt.structType, md) // must not panic
+
+			// Test the field functions.
+			m := reflect.New(tt.structType)
+			p := pointerOfValue(m)
+			for i, op := range tt.testOps {
+				switch op := op.(type) {
+				case hasOp:
+					got := map[pref.FieldNumber]bool{}
+					want := map[pref.FieldNumber]bool{}
+					for j, ok := range op {
+						n := pref.FieldNumber(j + 1)
+						got[n] = mi.fields[n].has(p)
+						want[n] = ok
+					}
+					if diff := cmp.Diff(want, got); diff != "" {
+						t.Errorf("operation %d, has mismatch (-want, +got):\n%s", i, diff)
+					}
+				case getOp:
+					got := map[pref.FieldNumber]pref.Value{}
+					want := map[pref.FieldNumber]pref.Value{}
+					for j, v := range op {
+						n := pref.FieldNumber(j + 1)
+						got[n] = mi.fields[n].get(p)
+						want[n] = v
+					}
+					xformValue := cmp.Transformer("", func(v pref.Value) interface{} {
+						return v.Interface()
+					})
+					if diff := cmp.Diff(want, got, xformValue); diff != "" {
+						t.Errorf("operation %d, get mismatch (-want, +got):\n%s", i, diff)
+					}
+				case setOp:
+					for j, v := range op {
+						n := pref.FieldNumber(j + 1)
+						mi.fields[n].set(p, v)
+					}
+				case clearOp:
+					for j, ok := range op {
+						n := pref.FieldNumber(j + 1)
+						if ok {
+							mi.fields[n].clear(p)
+						}
+					}
+				case equalOp:
+					got := m.Interface()
+					if diff := cmp.Diff(op.want, got); diff != "" {
+						t.Errorf("operation %d, equal mismatch (-want, +got):\n%s", i, diff)
+					}
+				}
+			}
+		})
+	}
+}