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package vfsutil
import (
"io"
"github.com/ncruces/go-sqlite3"
"github.com/ncruces/go-sqlite3/vfs"
)
// SliceFile implements [vfs.File] with a byte slice.
// It is suitable for temporary files (such as [vfs.OPEN_TEMP_JOURNAL]),
// but not concurrency safe.
type SliceFile []byte
var (
// Ensure these interfaces are implemented:
_ vfs.FileSizeHint = &SliceFile{}
)
// ReadAt implements [io.ReaderAt].
func (f *SliceFile) ReadAt(b []byte, off int64) (n int, err error) {
if d := *f; off < int64(len(d)) {
n = copy(b, d[off:])
}
if n < len(b) {
err = io.EOF
}
return
}
// WriteAt implements [io.WriterAt].
func (f *SliceFile) WriteAt(b []byte, off int64) (n int, err error) {
d := *f
if off > int64(len(d)) {
d = append(d, make([]byte, off-int64(len(d)))...)
}
d = append(d[:off], b...)
if len(d) > len(*f) {
*f = d
}
return len(b), nil
}
// Size implements [vfs.File].
func (f *SliceFile) Size() (int64, error) {
return int64(len(*f)), nil
}
// Truncate implements [vfs.File].
func (f *SliceFile) Truncate(size int64) error {
if d := *f; size < int64(len(d)) {
*f = d[:size]
}
return nil
}
// SizeHint implements [vfs.FileSizeHint].
func (f *SliceFile) SizeHint(size int64) error {
if d := *f; size > int64(len(d)) {
*f = append(d, make([]byte, size-int64(len(d)))...)
}
return nil
}
// Close implements [io.Closer].
func (*SliceFile) Close() error { return nil }
// Sync implements [vfs.File].
func (*SliceFile) Sync(flags vfs.SyncFlag) error { return nil }
// Lock implements [vfs.File].
func (*SliceFile) Lock(lock vfs.LockLevel) error {
// notest // not concurrency safe
return sqlite3.IOERR_LOCK
}
// Unlock implements [vfs.File].
func (*SliceFile) Unlock(lock vfs.LockLevel) error {
// notest // not concurrency safe
return sqlite3.IOERR_UNLOCK
}
// CheckReservedLock implements [vfs.File].
func (*SliceFile) CheckReservedLock() (bool, error) {
// notest // not concurrency safe
return false, sqlite3.IOERR_CHECKRESERVEDLOCK
}
// SectorSize implements [vfs.File].
func (*SliceFile) SectorSize() int {
// notest // safe default
return 0
}
// DeviceCharacteristics implements [vfs.File].
func (*SliceFile) DeviceCharacteristics() vfs.DeviceCharacteristic {
return vfs.IOCAP_ATOMIC |
vfs.IOCAP_SEQUENTIAL |
vfs.IOCAP_SAFE_APPEND |
vfs.IOCAP_POWERSAFE_OVERWRITE |
vfs.IOCAP_SUBPAGE_READ
}
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