// 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 fi, cache and bpool is optional and can be nil.
//
// The returned table reader instance is goroutine-safe.
func NewReader(f io.ReaderAt, size int64, fi *storage.FileInfo, cache *cache.CacheGetter, bpool *util.BufferPool, o *opt.Options) (*Reader, error) {
if f == nil {
return nil, errors.New("leveldb/table: nil file")
}
r := &Reader{
fi: fi,
reader: f,
cache: cache,
bpool: bpool,
o: o,
cmp: o.GetComparer(),
verifyChecksum: o.GetStrict(opt.StrictBlockChecksum),
}
if size < footerLen {
r.err = r.newErrCorrupted(0, size, "table", "too small")
return r, nil
}
footerPos := size - footerLen
var footer [footerLen]byte
if _, err := r.reader.ReadAt(footer[:], footerPos); err != nil && err != io.EOF {
return nil, err
}
if string(footer[footerLen-len(magic):footerLen]) != magic {
r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad magic number")
return r, nil
}
var n int
// Decode the metaindex block handle.
r.metaBH, n = decodeBlockHandle(footer[:])
if n == 0 {
r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad metaindex block handle")
return r, nil
}
// Decode the index block handle.
r.indexBH, n = decodeBlockHandle(footer[n:])
if n == 0 {
r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad index block handle")
return r, nil
}
// Read metaindex block.
metaBlock, err := r.readBlock(r.metaBH, true)
if err != nil {
if errors.IsCorrupted(err) {
r.err = err
return r, nil
} else {
return nil, err
}
}
// Set data end.
r.dataEnd = int64(r.metaBH.offset)
// Read metaindex.
metaIter := r.newBlockIter(metaBlock, nil, nil, true)
for metaIter.Next() {
key := string(metaIter.Key())
if !strings.HasPrefix(key, "filter.") {
continue
}
fn := key[7:]
if f0 := o.GetFilter(); f0 != nil && f0.Name() == fn {
r.filter = f0
} else {
for _, f0 := range o.GetAltFilters() {
if f0.Name() == fn {
r.filter = f0
break
}
}
}
if r.filter != nil {
filterBH, n := decodeBlockHandle(metaIter.Value())
if n == 0 {
continue
}
r.filterBH = filterBH
// Update data end.
r.dataEnd = int64(filterBH.offset)
break
}
}
metaIter.Release()
metaBlock.Release()
// Cache index and filter block locally, since we don't have global cache.
if cache == nil {
r.indexBlock, err = r.readBlock(r.indexBH, true)
if err != nil {
if errors.IsCorrupted(err) {
r.err = err
return r, nil
} else {
return nil, err
}
}
if r.filter != nil {
r.filterBlock, err = r.readFilterBlock(r.filterBH)
if err != nil {
if !errors.IsCorrupted(err) {
return nil, err
}
// Don't use filter then.
r.filter = nil
}
}
}
return r, nil
}