1 files changed, 368 insertions, 0 deletions
diff --git a/models/dbfs/dbfile.go b/models/dbfs/dbfile.go
new file mode 100644
index 00000000..dd27b5c3
--- /dev/null
+++ b/models/dbfs/dbfile.go
@@ -0,0 +1,368 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package dbfs
+
+import (
+	"context"
+	"errors"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+
+	"code.gitea.io/gitea/models/db"
+)
+
+var defaultFileBlockSize int64 = 32 * 1024
+
+type File interface {
+	io.ReadWriteCloser
+	io.Seeker
+	fs.File
+}
+
+type file struct {
+	ctx       context.Context
+	metaID    int64
+	fullPath  string
+	blockSize int64
+
+	allowRead  bool
+	allowWrite bool
+	offset     int64
+}
+
+var _ File = (*file)(nil)
+
+func (f *file) readAt(fileMeta *dbfsMeta, offset int64, p []byte) (n int, err error) {
+	if offset >= fileMeta.FileSize {
+		return 0, io.EOF
+	}
+
+	blobPos := int(offset % f.blockSize)
+	blobOffset := offset - int64(blobPos)
+	blobRemaining := int(f.blockSize) - blobPos
+	needRead := len(p)
+	if needRead > blobRemaining {
+		needRead = blobRemaining
+	}
+	if blobOffset+int64(blobPos)+int64(needRead) > fileMeta.FileSize {
+		needRead = int(fileMeta.FileSize - blobOffset - int64(blobPos))
+	}
+	if needRead <= 0 {
+		return 0, io.EOF
+	}
+	var fileData dbfsData
+	ok, err := db.GetEngine(f.ctx).Where("meta_id = ? AND blob_offset = ?", f.metaID, blobOffset).Get(&fileData)
+	if err != nil {
+		return 0, err
+	}
+	blobData := fileData.BlobData
+	if !ok {
+		blobData = nil
+	}
+
+	canCopy := len(blobData) - blobPos
+	if canCopy <= 0 {
+		canCopy = 0
+	}
+	realRead := needRead
+	if realRead > canCopy {
+		realRead = canCopy
+	}
+	if realRead > 0 {
+		copy(p[:realRead], fileData.BlobData[blobPos:blobPos+realRead])
+	}
+	for i := realRead; i < needRead; i++ {
+		p[i] = 0
+	}
+	return needRead, nil
+}
+
+func (f *file) Read(p []byte) (n int, err error) {
+	if f.metaID == 0 || !f.allowRead {
+		return 0, os.ErrInvalid
+	}
+
+	fileMeta, err := findFileMetaByID(f.ctx, f.metaID)
+	if err != nil {
+		return 0, err
+	}
+	n, err = f.readAt(fileMeta, f.offset, p)
+	f.offset += int64(n)
+	return n, err
+}
+
+func (f *file) Write(p []byte) (n int, err error) {
+	if f.metaID == 0 || !f.allowWrite {
+		return 0, os.ErrInvalid
+	}
+
+	fileMeta, err := findFileMetaByID(f.ctx, f.metaID)
+	if err != nil {
+		return 0, err
+	}
+
+	needUpdateSize := false
+	written := 0
+	for len(p) > 0 {
+		blobPos := int(f.offset % f.blockSize)
+		blobOffset := f.offset - int64(blobPos)
+		blobRemaining := int(f.blockSize) - blobPos
+		needWrite := len(p)
+		if needWrite > blobRemaining {
+			needWrite = blobRemaining
+		}
+		buf := make([]byte, f.blockSize)
+		readBytes, err := f.readAt(fileMeta, blobOffset, buf)
+		if err != nil && !errors.Is(err, io.EOF) {
+			return written, err
+		}
+		copy(buf[blobPos:blobPos+needWrite], p[:needWrite])
+		if blobPos+needWrite > readBytes {
+			buf = buf[:blobPos+needWrite]
+		} else {
+			buf = buf[:readBytes]
+		}
+
+		fileData := dbfsData{
+			MetaID:     fileMeta.ID,
+			BlobOffset: blobOffset,
+			BlobData:   buf,
+		}
+		if res, err := db.GetEngine(f.ctx).Exec("UPDATE dbfs_data SET revision=revision+1, blob_data=? WHERE meta_id=? AND blob_offset=?", buf, fileMeta.ID, blobOffset); err != nil {
+			return written, err
+		} else if updated, err := res.RowsAffected(); err != nil {
+			return written, err
+		} else if updated == 0 {
+			if _, err = db.GetEngine(f.ctx).Insert(&fileData); err != nil {
+				return written, err
+			}
+		}
+		written += needWrite
+		f.offset += int64(needWrite)
+		if f.offset > fileMeta.FileSize {
+			fileMeta.FileSize = f.offset
+			needUpdateSize = true
+		}
+		p = p[needWrite:]
+	}
+
+	fileMetaUpdate := dbfsMeta{
+		ModifyTimestamp: timeToFileTimestamp(time.Now()),
+	}
+	if needUpdateSize {
+		fileMetaUpdate.FileSize = f.offset
+	}
+	if _, err := db.GetEngine(f.ctx).ID(fileMeta.ID).Update(fileMetaUpdate); err != nil {
+		return written, err
+	}
+	return written, nil
+}
+
+func (f *file) Seek(n int64, whence int) (int64, error) {
+	if f.metaID == 0 {
+		return 0, os.ErrInvalid
+	}
+
+	newOffset := f.offset
+	switch whence {
+	case io.SeekStart:
+		newOffset = n
+	case io.SeekCurrent:
+		newOffset += n
+	case io.SeekEnd:
+		size, err := f.size()
+		if err != nil {
+			return f.offset, err
+		}
+		newOffset = size + n
+	default:
+		return f.offset, os.ErrInvalid
+	}
+	if newOffset < 0 {
+		return f.offset, os.ErrInvalid
+	}
+	f.offset = newOffset
+	return newOffset, nil
+}
+
+func (f *file) Close() error {
+	return nil
+}
+
+func (f *file) Stat() (os.FileInfo, error) {
+	if f.metaID == 0 {
+		return nil, os.ErrInvalid
+	}
+
+	fileMeta, err := findFileMetaByID(f.ctx, f.metaID)
+	if err != nil {
+		return nil, err
+	}
+	return fileMeta, nil
+}
+
+func timeToFileTimestamp(t time.Time) int64 {
+	return t.UnixMicro()
+}
+
+func fileTimestampToTime(timestamp int64) time.Time {
+	return time.UnixMicro(timestamp)
+}
+
+func (f *file) loadMetaByPath() error {
+	var fileMeta dbfsMeta
+	if ok, err := db.GetEngine(f.ctx).Where("full_path = ?", f.fullPath).Get(&fileMeta); err != nil {
+		return err
+	} else if ok {
+		f.metaID = fileMeta.ID
+		f.blockSize = fileMeta.BlockSize
+	}
+	return nil
+}
+
+func (f *file) open(flag int) (err error) {
+	// see os.OpenFile for flag values
+	if flag&os.O_WRONLY != 0 {
+		f.allowWrite = true
+	} else if flag&os.O_RDWR != 0 {
+		f.allowRead = true
+		f.allowWrite = true
+	} else /* O_RDONLY */ {
+		f.allowRead = true
+	}
+
+	if f.allowWrite {
+		if flag&os.O_CREATE != 0 {
+			if flag&os.O_EXCL != 0 {
+				// file must not exist.
+				if f.metaID != 0 {
+					return os.ErrExist
+				}
+			} else {
+				// create a new file if none exists.
+				if f.metaID == 0 {
+					if err = f.createEmpty(); err != nil {
+						return err
+					}
+				}
+			}
+		}
+		if flag&os.O_TRUNC != 0 {
+			if err = f.truncate(); err != nil {
+				return err
+			}
+		}
+		if flag&os.O_APPEND != 0 {
+			if _, err = f.Seek(0, io.SeekEnd); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	// read only mode
+	if f.metaID == 0 {
+		return os.ErrNotExist
+	}
+	return nil
+}
+
+func (f *file) createEmpty() error {
+	if f.metaID != 0 {
+		return os.ErrExist
+	}
+	now := time.Now()
+	_, err := db.GetEngine(f.ctx).Insert(&dbfsMeta{
+		FullPath:        f.fullPath,
+		BlockSize:       f.blockSize,
+		CreateTimestamp: timeToFileTimestamp(now),
+		ModifyTimestamp: timeToFileTimestamp(now),
+	})
+	if err != nil {
+		return err
+	}
+	return f.loadMetaByPath()
+}
+
+func (f *file) truncate() error {
+	if f.metaID == 0 {
+		return os.ErrNotExist
+	}
+	return db.WithTx(f.ctx, func(ctx context.Context) error {
+		if _, err := db.GetEngine(ctx).Exec("UPDATE dbfs_meta SET file_size = 0 WHERE id = ?", f.metaID); err != nil {
+			return err
+		}
+		if _, err := db.GetEngine(ctx).Delete(&dbfsData{MetaID: f.metaID}); err != nil {
+			return err
+		}
+		return nil
+	})
+}
+
+func (f *file) renameTo(newPath string) error {
+	if f.metaID == 0 {
+		return os.ErrNotExist
+	}
+	newPath = buildPath(newPath)
+	return db.WithTx(f.ctx, func(ctx context.Context) error {
+		if _, err := db.GetEngine(ctx).Exec("UPDATE dbfs_meta SET full_path = ? WHERE id = ?", newPath, f.metaID); err != nil {
+			return err
+		}
+		return nil
+	})
+}
+
+func (f *file) delete() error {
+	if f.metaID == 0 {
+		return os.ErrNotExist
+	}
+	return db.WithTx(f.ctx, func(ctx context.Context) error {
+		if _, err := db.GetEngine(ctx).Delete(&dbfsMeta{ID: f.metaID}); err != nil {
+			return err
+		}
+		if _, err := db.GetEngine(ctx).Delete(&dbfsData{MetaID: f.metaID}); err != nil {
+			return err
+		}
+		return nil
+	})
+}
+
+func (f *file) size() (int64, error) {
+	if f.metaID == 0 {
+		return 0, os.ErrNotExist
+	}
+	fileMeta, err := findFileMetaByID(f.ctx, f.metaID)
+	if err != nil {
+		return 0, err
+	}
+	return fileMeta.FileSize, nil
+}
+
+func findFileMetaByID(ctx context.Context, metaID int64) (*dbfsMeta, error) {
+	var fileMeta dbfsMeta
+	if ok, err := db.GetEngine(ctx).Where("id = ?", metaID).Get(&fileMeta); err != nil {
+		return nil, err
+	} else if ok {
+		return &fileMeta, nil
+	}
+	return nil, nil
+}
+
+func buildPath(path string) string {
+	path = filepath.Clean(path)
+	path = strings.ReplaceAll(path, "\\", "/")
+	path = strings.TrimPrefix(path, "/")
+	return strconv.Itoa(strings.Count(path, "/")) + ":" + path
+}
+
+func newDbFile(ctx context.Context, path string) (*file, error) {
+	path = buildPath(path)
+	f := &file{ctx: ctx, fullPath: path, blockSize: defaultFileBlockSize}
+	return f, f.loadMetaByPath()
+}