[wip] lib/binary: implement BigEndianFile

lib/binary/big_endian_file.go

@@ -0,0 +1,78 @@
+// SPDX-FileCopyrightText: 2024 M. Shulhan <ms@kilabit.info>
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+package binary
+
+import (
+	"fmt"
+	"os"
+	"sync"
+)
+
+// BigEndianFile support reading and writing Go types into file with
+// big-endian byte order.
+// Unlike [binary.Write] in the standard library, the Write method in here
+// support writing struct field with type slice and string.
+type BigEndianFile struct {
+	name string
+	file *os.File
+
+	// val is the backing storage for the file.
+	val []byte
+
+	mtx sync.Mutex
+}
+
+// OpenBigEndianFile open the file for read and write.
+// It will return an error if file does not exists.
+func OpenBigEndianFile(name string) (bef *BigEndianFile, err error) {
+	var logp = `OpenBigEndianFile`
+
+	bef = &BigEndianFile{
+		name: name,
+	}
+
+	bef.file, err = os.OpenFile(name, os.O_RDWR, 0600)
+	if err != nil {
+		return nil, fmt.Errorf(`%s: %w`, logp, err)
+	}
+
+	var fi os.FileInfo
+	fi, err = bef.file.Stat()
+	if err != nil {
+		goto fail
+	}
+
+	bef.val = make([]byte, fi.Size())
+
+	// Read all contents.
+	_, err = bef.file.Read(bef.val)
+	if err != nil {
+		goto fail
+	}
+
+	return bef, nil
+fail:
+	_ = bef.file.Close()
+	return nil, fmt.Errorf(`%s: %w`, logp, err)
+}
+
+func (bef *BigEndianFile) Close() (err error) {
+	bef.mtx.Lock()
+	err = bef.file.Close()
+	bef.mtx.Unlock()
+	return err
+}
+
+func (bef *BigEndianFile) Read(data any) (err error) {
+	return nil
+}
+
+func (bef *BigEndianFile) Seek(off int64, whence int) (n int64, err error) {
+	return n, nil
+}
+
+func (bef *BigEndianFile) Write(data any) (n int64, err error) {
+	return n, nil
+}

lib/binary/big_endian_file_test.go

@@ -0,0 +1,47 @@
+// SPDX-FileCopyrightText: 2024 M. Shulhan <ms@kilabit.info>
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+package binary
+
+import (
+	"testing"
+
+	"git.sr.ht/~shulhan/pakakeh.go/lib/test"
+)
+
+type testBigEndian struct {
+	data any
+	tag  string
+}
+
+func TestOpenBigEndianFile(t *testing.T) {
+	listCase := []struct {
+		name     string
+		expError string
+		expVal   string
+	}{{
+		name:     `notexist`,
+		expError: `OpenBigEndianFile: open notexist: no such file or directory`,
+	}, {
+		name:   `testdata/BigEndianFile/open`,
+		expVal: "Test OpenBigEndianFile\n",
+	}}
+
+	for _, tcase := range listCase {
+		bef, err := OpenBigEndianFile(tcase.name)
+		if err != nil {
+			test.Assert(t, tcase.name+` error`,
+				tcase.expError, err.Error())
+			continue
+		}
+
+		test.Assert(t, `name`, tcase.name, bef.name)
+		test.Assert(t, `val`, tcase.expVal, string(bef.val))
+
+		err = bef.Close()
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}

lib/binary/testdata/BigEndianFile/open

@@ -0,0 +1 @@
+Test OpenBigEndianFile