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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package streamio
import (
"bufio"
"context"
"io"
"os"
"time"
"github.com/datawire/dlib/dlog"
"git.lukeshu.com/btrfs-progs-ng/lib/textui"
)
type RuneScanner interface {
io.RuneScanner
io.Closer
}
type runeScanner struct {
ctx context.Context //nolint:containedctx // For detecting shutdown from methods
done <-chan struct{}
progress textui.Portion[int64]
progressWriter *textui.Progress[textui.Portion[int64]]
unreadCnt uint64
reader *bufio.Reader
closer io.Closer
}
// NewRuneScanner returns an io.RuneScanner (and io.Closer) that
// bufferes a file, similar to bufio.NewReader. There are two
// advantages over bufio.NewReader:
//
// - It takes a Context, and causes reads to fail once the Context is
// canceled; allowing large parse operations to be gracefully cut
// short.
//
// - It logs the progress of reading the file via textui.Progress.
func NewRuneScanner(ctx context.Context, fh *os.File) (RuneScanner, error) {
fi, err := fh.Stat()
if err != nil {
return nil, err
}
ret := &runeScanner{
ctx: ctx,
done: ctx.Done(),
progress: textui.Portion[int64]{
D: fi.Size(),
},
progressWriter: textui.NewProgress[textui.Portion[int64]](ctx, dlog.LogLevelInfo, textui.Tunable(1*time.Second)),
reader: bufio.NewReader(fh),
closer: fh,
}
return ret, nil
}
func isClosed(ch <-chan struct{}) bool {
select {
case <-ch:
return true
default:
return false
}
}
//nolint:gomnd // False positive: gomnd.ignored-functions=[textui.Tunable] doesn't support type params.
var runeThrottle = textui.Tunable[int64](64)
// ReadRune implements io.RuneReader.
func (rs *runeScanner) ReadRune() (r rune, size int, err error) {
// According to the profiler, checking if the rs.ctx.Done()
// channel is closed is faster than checking if rs.ctx.Err()
// is non-nil.
if rs.unreadCnt == 0 && isClosed(rs.done) {
return 0, 0, rs.ctx.Err()
}
r, size, err = rs.reader.ReadRune()
if rs.unreadCnt > 0 {
rs.unreadCnt--
} else {
rs.progress.N += int64(size)
if rs.progress.D < runeThrottle || rs.progress.N%runeThrottle == 0 || rs.progress.N > rs.progress.D-runeThrottle {
rs.progressWriter.Set(rs.progress)
}
}
return
}
// ReadRune implements io.RuneScanner.
func (rs *runeScanner) UnreadRune() error {
if err := rs.reader.UnreadRune(); err != nil {
return err
}
rs.unreadCnt++
return nil
}
// ReadRune implements io.Closer.
func (rs *runeScanner) Close() error {
rs.progressWriter.Done()
return rs.closer.Close()
}
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