func (s *session) setOptions(o *opt.Options) {
s.o = &opt.Options{}
if o != nil {
*s.o = *o
}
// Alternative filters.
if filters := o.GetAltFilters(); len(filters) > 0 {
s.o.AltFilters = make([]filter.Filter, len(filters))
for i, filter := range filters {
s.o.AltFilters[i] = &iFilter{filter}
}
}
// Block cache.
switch o.GetBlockCache() {
case nil:
s.o.BlockCache = cache.NewLRUCache(opt.DefaultBlockCacheSize)
case opt.NoCache:
s.o.BlockCache = nil
}
// Comparer.
s.cmp = &iComparer{o.GetComparer()}
s.o.Comparer = s.cmp
// Filter.
if filter := o.GetFilter(); filter != nil {
s.o.Filter = &iFilter{filter}
}
}
// NewWriter creates a new initialized table writer for the file.
//
// Table writer is not goroutine-safe.
func NewWriter(f io.Writer, o *opt.Options) *Writer {
w := &Writer{
writer: f,
cmp: o.GetComparer(),
filter: o.GetFilter(),
compression: o.GetCompression(),
blockSize: o.GetBlockSize(),
comparerScratch: make([]byte, 0),
}
// data block
w.dataBlock.restartInterval = o.GetBlockRestartInterval()
// The first 20-bytes are used for encoding block handle.
w.dataBlock.scratch = w.scratch[20:]
// index block
w.indexBlock.restartInterval = 1
w.indexBlock.scratch = w.scratch[20:]
// filter block
if w.filter != nil {
w.filterBlock.generator = w.filter.NewGenerator()
w.filterBlock.flush(0)
}
return w
}
// NewReader creates a new initialized table reader for the file.
// The cache is optional and can be nil.
func NewReader(f io.ReaderAt, size int64, cache cache.Namespace, o *opt.Options) *Reader {
r := &Reader{
reader: f,
cache: cache,
cmp: o.GetComparer(),
checksum: o.GetStrict(opt.StrictBlockChecksum),
strictIter: o.GetStrict(opt.StrictIterator),
}
if f == nil {
r.err = errors.New("leveldb/table: Reader: nil file")
return r
}
if size < footerLen {
r.err = errors.New("leveldb/table: Reader: invalid table (file size is too small)")
return r
}
var footer [footerLen]byte
if _, err := r.reader.ReadAt(footer[:], size-footerLen); err != nil && err != io.EOF {
r.err = fmt.Errorf("leveldb/table: Reader: invalid table (could not read footer): %v", err)
}
if string(footer[footerLen-len(magic):footerLen]) != magic {
r.err = errors.New("leveldb/table: Reader: invalid table (bad magic number)")
return r
}
// Decode the metaindex block handle.
metaBH, n := decodeBlockHandle(footer[:])
if n == 0 {
r.err = errors.New("leveldb/table: Reader: invalid table (bad metaindex block handle)")
return r
}
// Decode the index block handle.
indexBH, n := decodeBlockHandle(footer[n:])
if n == 0 {
r.err = errors.New("leveldb/table: Reader: invalid table (bad index block handle)")
return r
}
// Read index block.
r.indexBlock, r.err = r.readBlock(indexBH, true)
if r.err != nil {
return r
}
// Read metaindex block.
metaBlock, err := r.readBlock(metaBH, true)
if err != nil {
r.err = err
return r
}
// Set data end.
r.dataEnd = int64(metaBH.offset)
metaIter := metaBlock.newIterator(nil, false, nil)
for metaIter.Next() {
key := string(metaIter.Key())
if !strings.HasPrefix(key, "filter.") {
continue
}
fn := key[7:]
var filter filter.Filter
if f0 := o.GetFilter(); f0 != nil && f0.Name() == fn {
filter = f0
} else {
for _, f0 := range o.GetAltFilters() {
if f0.Name() == fn {
filter = f0
break
}
}
}
if filter != nil {
filterBH, n := decodeBlockHandle(metaIter.Value())
if n == 0 {
continue
}
// Update data end.
r.dataEnd = int64(filterBH.offset)
filterBlock, err := r.readFilterBlock(filterBH, filter)
if err != nil {
continue
}
r.filterBlock = filterBlock
break
}
}
metaIter.Release()
return r
}