[#316] locode: Implement csv UN/LOCODE table

Define csv UN/LOCODE table. Implement iterator over table entries. Implement
method that resolves country/subdivision code pair to subdivision name.

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

pkg/util/locode/table/csv/calls.go

@@ -0,0 +1,120 @@
+package csvlocode
+
+import (
+	"encoding/csv"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/nspcc-dev/neofs-node/pkg/util/locode"
+	locodedb "github.com/nspcc-dev/neofs-node/pkg/util/locode/db"
+	"github.com/pkg/errors"
+)
+
+var errInvalidRecord = errors.New("invalid table record")
+
+// IterateAll scans table record one-by-one, parses UN/LOCODE record
+// from it and passes it to f.
+//
+// Returns f's errors directly.
+func (t *Table) IterateAll(f func(locode.Record) error) error {
+	const wordsPerRecord = 12
+
+	return t.scanWords(t.paths, wordsPerRecord, func(words []string) error {
+		lc, err := locode.FromString(strings.Join(words[1:3], " "))
+		if err != nil {
+			return err
+		}
+
+		record := locode.Record{
+			Ch:               words[0],
+			LOCODE:           *lc,
+			Name:             words[3],
+			NameWoDiacritics: words[4],
+			SubDiv:           words[5],
+			Function:         words[6],
+			Status:           words[7],
+			Date:             words[8],
+			IATA:             words[9],
+			Coordinates:      words[10],
+			Remarks:          words[11],
+		}
+
+		return f(record)
+	})
+}
+
+// SubDivName scans table record one-by-one, and returns subdivision name
+// on country and subdivision codes match.
+//
+// Returns locodedb.ErrSubDivNotFound if no entry matches.
+func (t *Table) SubDivName(countryCode *locodedb.CountryCode, name string) (subDiv string, err error) {
+	const wordsPerRecord = 4
+
+	err = t.scanWords([]string{t.subDivPath}, wordsPerRecord, func(words []string) error {
+		if words[0] == countryCode.String() && words[1] == name {
+			subDiv = words[2]
+			return errScanInt
+		}
+
+		return nil
+	})
+
+	if err == nil && subDiv == "" {
+		err = locodedb.ErrSubDivNotFound
+	}
+
+	return
+}
+
+var errScanInt = errors.New("interrupt scan")
+
+func (t *Table) scanWords(paths []string, fpr int, wordsHandler func([]string) error) error {
+	var (
+		rdrs    = make([]io.Reader, 0, len(t.paths))
+		closers = make([]io.Closer, 0, len(t.paths))
+	)
+
+	for i := range paths {
+		file, err := os.OpenFile(paths[i], os.O_RDONLY, t.mode)
+		if err != nil {
+			return err
+		}
+
+		rdrs = append(rdrs, file)
+		closers = append(closers, file)
+	}
+
+	defer func() {
+		for i := range closers {
+			_ = closers[i].Close()
+		}
+	}()
+
+	r := csv.NewReader(io.MultiReader(rdrs...))
+	r.ReuseRecord = true
+	r.FieldsPerRecord = fpr
+
+	for {
+		words, err := r.Read()
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				break
+			}
+
+			return err
+		} else if len(words) != fpr {
+			return errInvalidRecord
+		}
+
+		if err := wordsHandler(words); err != nil {
+			if errors.Is(err, errScanInt) {
+				break
+			}
+
+			return err
+		}
+	}
+
+	return nil
+}