Implement kaitai.Struct common interface

.golangci.yml

@@ -87,3 +87,4 @@ issues:
   # excluded by default patterns execute `golangci-lint run --help`
   exclude:
      - Using the variable on range scope `tt` in function literal
+     - "var-naming: don't use underscores in Go names; method IO_ should be IO"

go.mod

@@ -2,4 +2,7 @@ module github.com/kaitai-io/kaitai_struct_go_runtime
 
 go 1.13
 
-require golang.org/x/text v0.14.0
+require (
+	github.com/stretchr/testify v1.9.0 // indirect
+	golang.org/x/text v0.14.0
+)

go.sum

@@ -1,3 +1,17 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
@@ -30,3 +44,7 @@ golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtn
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

kaitai/struct.go

@@ -0,0 +1,12 @@
+package kaitai
+
+// Struct is the common interface guaranteed to be implemented by all types generated by
+// Kaitai Struct compiler.
+type Struct interface {
+	// IO_ returns the stream object associated with the struct.
+	//
+	// This is deliberately named with a `_` suffix to avoid conflicts with other methods
+	// that may result from the attributes in Kaitai Struct type, e.g. if a user will define
+	// attribute `i_o` this will conflict with the method `IO()`.
+	IO_() *Stream
+}

kaitai/struct_test.go

@@ -0,0 +1,48 @@
+package kaitai
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Declare two struct simulating types generated by Kaitai Struct compiler
+type oneStruct struct {
+	one int
+	_io *Stream
+}
+
+func (s *oneStruct) IO_() *Stream {
+	return s._io
+}
+
+type twoStruct struct {
+	two int
+	_io *Stream
+}
+
+func (s *twoStruct) IO_() *Stream {
+	return s._io
+}
+
+func WorkWithStruct(t *testing.T, s Struct, expectedSize int) {
+	t.Helper()
+	actualSize, err := s.IO_().Size()
+	assert.Nil(t, err)
+	assert.Equal(t, actualSize, int64(expectedSize))
+}
+
+func TestKaitaiStruct(t *testing.T) {
+	// Instantiate streams for the structs
+	oneStream := NewStream(bytes.NewReader([]byte("a quick")))
+	twoStream := NewStream(bytes.NewReader([]byte("brown fox")))
+
+	// Instantiate the structs
+	one := oneStruct{111, oneStream}
+	two := twoStruct{222, twoStream}
+
+	// Check if the structs implement the Struct interface
+	WorkWithStruct(t, &one, 7)
+	WorkWithStruct(t, &two, 9)
+}