| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package compress |
| |
| import ( |
| "bytes" |
| "io" |
| "io/ioutil" |
| |
| "github.com/andybalholm/brotli" |
| "github.com/apache/arrow/go/v6/parquet/internal/debug" |
| ) |
| |
| type brotliCodec struct{} |
| |
| func (brotliCodec) NewReader(r io.Reader) io.ReadCloser { |
| return ioutil.NopCloser(brotli.NewReader(r)) |
| } |
| |
| func (b brotliCodec) EncodeLevel(dst, src []byte, level int) []byte { |
| if level == DefaultCompressionLevel { |
| level = brotli.DefaultCompression |
| } |
| |
| maxlen := int(b.CompressBound(int64(len(src)))) |
| if dst == nil || cap(dst) < maxlen { |
| dst = make([]byte, 0, maxlen) |
| } |
| buf := bytes.NewBuffer(dst[:0]) |
| w := brotli.NewWriterLevel(buf, level) |
| _, err := w.Write(src) |
| if err != nil { |
| panic(err) |
| } |
| if err := w.Close(); err != nil { |
| panic(err) |
| } |
| return buf.Bytes() |
| } |
| |
| func (b brotliCodec) Encode(dst, src []byte) []byte { |
| return b.EncodeLevel(dst, src, brotli.DefaultCompression) |
| } |
| |
| func (brotliCodec) Decode(dst, src []byte) []byte { |
| rdr := brotli.NewReader(bytes.NewReader(src)) |
| if dst != nil { |
| var ( |
| sofar = 0 |
| n = -1 |
| err error = nil |
| ) |
| for n != 0 && err == nil { |
| n, err = rdr.Read(dst[sofar:]) |
| sofar += n |
| } |
| if err != nil && err != io.EOF { |
| panic(err) |
| } |
| return dst[:sofar] |
| } |
| |
| dst, err := ioutil.ReadAll(rdr) |
| if err != nil { |
| panic(err) |
| } |
| |
| return dst |
| } |
| |
| // taken from brotli/enc/encode.c:1426 |
| // BrotliEncoderMaxCompressedSize |
| func (brotliCodec) CompressBound(len int64) int64 { |
| // [window bits / empty metadata] + N * [uncompressed] + [last empty] |
| debug.Assert(len > 0, "brotli compressbound should be > 0") |
| nlarge := len >> 14 |
| overhead := 2 + (4 * nlarge) + 3 + 1 |
| result := len + overhead |
| if len == 0 { |
| return 2 |
| } |
| if result < len { |
| return 0 |
| } |
| return len |
| } |
| |
| func (brotliCodec) NewWriter(w io.Writer) io.WriteCloser { |
| return brotli.NewWriter(w) |
| } |
| |
| func (brotliCodec) NewWriterLevel(w io.Writer, level int) (io.WriteCloser, error) { |
| if level == DefaultCompressionLevel { |
| level = brotli.DefaultCompression |
| } |
| return brotli.NewWriterLevel(w, level), nil |
| } |
| |
| func init() { |
| codecs[Codecs.Brotli] = brotliCodec{} |
| } |