/
zlib.go
81 lines (67 loc) · 2.03 KB
/
zlib.go
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// 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 compression
import (
"bytes"
"compress/zlib"
"io"
)
type zlibProvider struct{}
// NewZLibProvider returns a Provider interface
func NewZLibProvider() Provider {
return &zlibProvider{}
}
func (zlibProvider) CompressMaxSize(originalSize int) int {
// Use formula from ZLib: https://github.com/madler/zlib/blob/cacf7f1d4e3d44d871b605da3b647f07d718623f/deflate.c#L659
return originalSize +
((originalSize + 7) >> 3) + ((originalSize + 63) >> 6) + 11
}
func (zlibProvider) Compress(dst, src []byte) []byte {
var b = bytes.NewBuffer(dst[:0])
w := zlib.NewWriter(b)
if _, err := w.Write(src); err != nil {
return nil
}
if err := w.Close(); err != nil {
return nil
}
return b.Bytes()
}
func (zlibProvider) Decompress(dst, src []byte, originalSize int) ([]byte, error) {
r, err := zlib.NewReader(bytes.NewReader(src))
if err != nil {
return nil, err
}
if cap(dst) >= originalSize {
dst = dst[0:originalSize] // Reuse dst buffer
} else {
dst = make([]byte, originalSize)
}
if _, err = io.ReadFull(r, dst); err != nil {
return nil, err
}
if err = r.Close(); err != nil {
return nil, err
}
return dst, nil
}
func (zlibProvider) Clone() Provider {
return NewZLibProvider()
}
func (zlibProvider) Close() error {
return nil
}