feat(stream): support using temporary files as large buffer (#1399)

feat(stream): refactor StreamSectionReader to support using temporary files as large buffer

internal/stream/util.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
 
 	"github.com/OpenListTeam/OpenList/v4/internal/conf"
 	"github.com/OpenListTeam/OpenList/v4/internal/model"
@@ -151,32 +152,58 @@ func CacheFullAndHash(stream model.FileStreamer, up *model.UpdateProgress, hashT
 	return tmpF, hex.EncodeToString(h.Sum(nil)), nil
 }
 
-type StreamSectionReader struct {
-	file    model.FileStreamer
-	off     int64
-	bufPool *pool.Pool[[]byte]
+type StreamSectionReaderIF interface {
+	// 线程不安全
+	GetSectionReader(off, length int64) (io.ReadSeeker, error)
+	FreeSectionReader(sr io.ReadSeeker)
+	// 线程不安全
+	DiscardSection(off int64, length int64) error
 }
 
-func NewStreamSectionReader(file model.FileStreamer, maxBufferSize int, up *model.UpdateProgress) (*StreamSectionReader, error) {
-	ss := &StreamSectionReader{file: file}
+func NewStreamSectionReader(file model.FileStreamer, maxBufferSize int, up *model.UpdateProgress) (StreamSectionReaderIF, error) {
 	if file.GetFile() != nil {
-		return ss, nil
+		return &cachedSectionReader{file.GetFile()}, nil
 	}
 
 	maxBufferSize = min(maxBufferSize, int(file.GetSize()))
 	if maxBufferSize > conf.MaxBufferLimit {
-		_, err := file.CacheFullAndWriter(up, nil)
+		f, err := os.CreateTemp(conf.Conf.TempDir, "file-*")
 		if err != nil {
 			return nil, err
 		}
+
+		if f.Truncate((file.GetSize()+int64(maxBufferSize-1))/int64(maxBufferSize)*int64(maxBufferSize)) != nil {
+			// fallback to full cache
+			_, _ = f.Close(), os.Remove(f.Name())
+			cache, err := file.CacheFullAndWriter(up, nil)
+			if err != nil {
+				return nil, err
+			}
+			return &cachedSectionReader{cache}, nil
+		}
+
+		ss := &fileSectionReader{Reader: file, temp: f}
+		ss.bufPool = &pool.Pool[*offsetWriterWithBase]{
+			New: func() *offsetWriterWithBase {
+				base := ss.fileOff
+				ss.fileOff += int64(maxBufferSize)
+				return &offsetWriterWithBase{io.NewOffsetWriter(ss.temp, base), base}
+			},
+		}
+		file.Add(utils.CloseFunc(func() error {
+			ss.bufPool.Reset()
+			return errors.Join(ss.temp.Close(), os.Remove(ss.temp.Name()))
+		}))
 		return ss, nil
 	}
+
+	ss := &directSectionReader{file: file}
 	if conf.MmapThreshold > 0 && maxBufferSize >= conf.MmapThreshold {
 		ss.bufPool = &pool.Pool[[]byte]{
 			New: func() []byte {
 				buf, err := mmap.Alloc(maxBufferSize)
 				if err == nil {
-					file.Add(utils.CloseFunc(func() error {
+					ss.file.Add(utils.CloseFunc(func() error {
 						return mmap.Free(buf)
 					}))
 				} else {
@@ -200,53 +227,113 @@ func NewStreamSectionReader(file model.FileStreamer, maxBufferSize int, up *mode
 	return ss, nil
 }
 
+type cachedSectionReader struct {
+	cache io.ReaderAt
+}
+
+func (*cachedSectionReader) DiscardSection(off int64, length int64) error {
+	return nil
+}
+func (s *cachedSectionReader) GetSectionReader(off, length int64) (io.ReadSeeker, error) {
+	return io.NewSectionReader(s.cache, off, length), nil
+}
+func (*cachedSectionReader) FreeSectionReader(sr io.ReadSeeker) {}
+
+type fileSectionReader struct {
+	io.Reader
+	off     int64
+	temp    *os.File
+	fileOff int64
+	bufPool *pool.Pool[*offsetWriterWithBase]
+}
+
+type offsetWriterWithBase struct {
+	*io.OffsetWriter
+	base int64
+}
+
 // 线程不安全
-func (ss *StreamSectionReader) DiscardSection(off int64, length int64) error {
-	if ss.file.GetFile() == nil {
-		if off != ss.off {
-			return fmt.Errorf("stream not cached: request offset %d != current offset %d", off, ss.off)
-		}
-		_, err := utils.CopyWithBufferN(io.Discard, ss.file, length)
-		if err != nil {
-			return fmt.Errorf("failed to skip data: (expect =%d) %w", length, err)
-		}
+func (ss *fileSectionReader) DiscardSection(off int64, length int64) error {
+	if off != ss.off {
+		return fmt.Errorf("stream not cached: request offset %d != current offset %d", off, ss.off)
+	}
+	_, err := utils.CopyWithBufferN(io.Discard, ss.Reader, length)
+	if err != nil {
+		return fmt.Errorf("failed to skip data: (expect =%d) %w", length, err)
 	}
 	ss.off += length
 	return nil
 }
 
-// 线程不安全
-func (ss *StreamSectionReader) GetSectionReader(off, length int64) (*SectionReader, error) {
-	var cache io.ReaderAt = ss.file.GetFile()
-	var buf []byte
-	if cache == nil {
-		if off != ss.off {
-			return nil, fmt.Errorf("stream not cached: request offset %d != current offset %d", off, ss.off)
-		}
-		tempBuf := ss.bufPool.Get()
-		buf = tempBuf[:length]
-		n, err := io.ReadFull(ss.file, buf)
-		if int64(n) != length {
-			return nil, fmt.Errorf("failed to read all data: (expect =%d, actual =%d) %w", length, n, err)
-		}
-		ss.off += int64(n)
-		off = 0
-		cache = bytes.NewReader(buf)
-	}
-	return &SectionReader{io.NewSectionReader(cache, off, length), buf}, nil
+type fileBufferSectionReader struct {
+	io.ReadSeeker
+	fileBuf *offsetWriterWithBase
 }
 
-func (ss *StreamSectionReader) FreeSectionReader(sr *SectionReader) {
-	if sr != nil {
-		if sr.buf != nil {
-			ss.bufPool.Put(sr.buf[0:cap(sr.buf)])
-			sr.buf = nil
-		}
+func (ss *fileSectionReader) GetSectionReader(off, length int64) (io.ReadSeeker, error) {
+	if off != ss.off {
+		return nil, fmt.Errorf("stream not cached: request offset %d != current offset %d", off, ss.off)
+	}
+	fileBuf := ss.bufPool.Get()
+	_, _ = fileBuf.Seek(0, io.SeekStart)
+	n, err := utils.CopyWithBufferN(fileBuf, ss.Reader, length)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read all data: (expect =%d, actual =%d) %w", length, n, err)
+	}
+	ss.off += length
+	return &fileBufferSectionReader{io.NewSectionReader(ss.temp, fileBuf.base, length), fileBuf}, nil
+}
+
+func (ss *fileSectionReader) FreeSectionReader(rs io.ReadSeeker) {
+	if sr, ok := rs.(*fileBufferSectionReader); ok {
+		ss.bufPool.Put(sr.fileBuf)
+		sr.fileBuf = nil
 		sr.ReadSeeker = nil
 	}
 }
 
-type SectionReader struct {
+type directSectionReader struct {
+	file    model.FileStreamer
+	off     int64
+	bufPool *pool.Pool[[]byte]
+}
+
+// 线程不安全
+func (ss *directSectionReader) DiscardSection(off int64, length int64) error {
+	if off != ss.off {
+		return fmt.Errorf("stream not cached: request offset %d != current offset %d", off, ss.off)
+	}
+	_, err := utils.CopyWithBufferN(io.Discard, ss.file, length)
+	if err != nil {
+		return fmt.Errorf("failed to skip data: (expect =%d) %w", length, err)
+	}
+	ss.off += length
+	return nil
+}
+
+type bufferSectionReader struct {
 	io.ReadSeeker
 	buf []byte
 }
+
+// 线程不安全
+func (ss *directSectionReader) GetSectionReader(off, length int64) (io.ReadSeeker, error) {
+	if off != ss.off {
+		return nil, fmt.Errorf("stream not cached: request offset %d != current offset %d", off, ss.off)
+	}
+	tempBuf := ss.bufPool.Get()
+	buf := tempBuf[:length]
+	n, err := io.ReadFull(ss.file, buf)
+	if int64(n) != length {
+		return nil, fmt.Errorf("failed to read all data: (expect =%d, actual =%d) %w", length, n, err)
+	}
+	ss.off += int64(n)
+	return &bufferSectionReader{bytes.NewReader(buf), buf}, nil
+}
+func (ss *directSectionReader) FreeSectionReader(rs io.ReadSeeker) {
+	if sr, ok := rs.(*bufferSectionReader); ok {
+		ss.bufPool.Put(sr.buf[0:cap(sr.buf)])
+		sr.buf = nil
+		sr.ReadSeeker = nil
+	}
+}