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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package main
import (
"bufio"
"context"
"io"
"os"
"time"
"git.lukeshu.com/go/lowmemjson"
"github.com/datawire/dlib/dlog"
"git.lukeshu.com/btrfs-progs-ng/lib/textui"
)
type runeScanner struct {
progress textui.Portion[int64]
progressWriter *textui.Progress[textui.Portion[int64]]
unreadCnt uint64
reader *bufio.Reader
closer io.Closer
}
func newRuneScanner(ctx context.Context, fh *os.File) (*runeScanner, error) {
fi, err := fh.Stat()
if err != nil {
return nil, err
}
ret := &runeScanner{
progress: textui.Portion[int64]{
D: fi.Size(),
},
progressWriter: textui.NewProgress[textui.Portion[int64]](ctx, dlog.LogLevelInfo, 1*time.Second),
reader: bufio.NewReader(fh),
closer: fh,
}
return ret, nil
}
func (rs *runeScanner) ReadRune() (r rune, size int, err error) {
r, size, err = rs.reader.ReadRune()
if rs.unreadCnt > 0 {
rs.unreadCnt--
} else {
rs.progress.N += int64(size)
rs.progressWriter.Set(rs.progress)
}
return
}
func (rs *runeScanner) UnreadRune() error {
rs.unreadCnt++
return rs.reader.UnreadRune()
}
func (rs *runeScanner) Close() error {
rs.progressWriter.Done()
return rs.closer.Close()
}
func readJSONFile[T any](ctx context.Context, filename string) (T, error) {
fh, err := os.Open(filename)
if err != nil {
var zero T
return zero, err
}
buf, err := newRuneScanner(dlog.WithField(ctx, "btrfs.read-json-file", filename), fh)
if err != nil {
var zero T
return zero, err
}
var ret T
if err := lowmemjson.DecodeThenEOF(buf, &ret); err != nil {
var zero T
return zero, err
}
_ = buf.Close()
return ret, nil
}
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