[#316] locode: Implement NeoFS location database based on BoltDB instance

Define NeoFS location database based on BoltDB. Implement methods to save
the record by key (Put) and to read the record by key (Get).

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/util/locode/db/boltdb/db.go

@@ -0,0 +1,73 @@
+package locodebolt
+
+import (
+	"fmt"
+	"os"
+
+	"go.etcd.io/bbolt"
+)
+
+// Prm groups the required parameters of the DB's constructor.
+//
+// All values must comply with the requirements imposed on them.
+// Passing incorrect parameter values will result in constructor
+// failure (error or panic depending on the implementation).
+type Prm struct {
+	// Path to BoltDB file with NeoFS location database.
+	//
+	// Must not be empty.
+	Path string
+}
+
+// DB is a descriptor of the NeoFS BoltDB location database.
+//
+// For correct operation, DB must be created
+// using the constructor (New) based on the required parameters
+// and optional components.
+//
+// After successful creation,
+// DB must be opened through Open call. After successful opening,
+// DB is ready to work through API (until Close call).
+//
+// Upon completion of work with the DB, it must be closed
+// by Close method.
+type DB struct {
+	path string
+
+	mode os.FileMode
+
+	boltOpts *bbolt.Options
+
+	bolt *bbolt.DB
+}
+
+const invalidPrmValFmt = "invalid parameter %s (%T):%v"
+
+func panicOnPrmValue(n string, v interface{}) {
+	panic(fmt.Sprintf(invalidPrmValFmt, n, v, v))
+}
+
+// New creates a new instance of the DB.
+//
+// Panics if at least one value of the parameters is invalid.
+//
+// The created DB requires calling the Open method in order
+// to initialize required resources.
+func New(prm Prm, opts ...Option) *DB {
+	switch {
+	case prm.Path == "":
+		panicOnPrmValue("Path", prm.Path)
+	}
+
+	o := defaultOpts()
+
+	for i := range opts {
+		opts[i](o)
+	}
+
+	return &DB{
+		path:     prm.Path,
+		mode:     o.mode,
+		boltOpts: o.boltOpts,
+	}
+}