/
compression.go
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/
compression.go
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//
// Copyright (c) 2017 Cavium
// Copyright (c) 2021 Intel Corporation
//
// Licensed 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 transforms
import (
"bytes"
"compress/gzip"
"compress/zlib"
"encoding/base64"
"fmt"
"sync"
"github.com/edgexfoundry/go-mod-core-contracts/v3/clients/logger"
"github.com/edgexfoundry/app-functions-sdk-go/v3/pkg/interfaces"
"github.com/edgexfoundry/app-functions-sdk-go/v3/pkg/util"
"github.com/edgexfoundry/go-mod-core-contracts/v3/common"
)
type Compression struct {
gzipWriter *gzip.Writer
zlibWriter *zlib.Writer
mutex sync.Mutex
}
// NewCompression creates, initializes and returns a new instance of Compression
func NewCompression() *Compression {
return &Compression{}
}
// CompressWithGZIP compresses data received as either a string,[]byte, or json.Marshaller using gzip algorithm
// and returns a base64 encoded string as a []byte.
func (compression *Compression) CompressWithGZIP(ctx interfaces.AppFunctionContext, data interface{}) (bool, interface{}) {
// as gzip writer is not allowed to be used by multiple goroutines, to avoid data race, use mutex lock to ensure atomic gzip writer operation.
compression.mutex.Lock()
defer compression.mutex.Unlock()
if data == nil {
// We didn't receive a result
return false, fmt.Errorf("function CompressWithGZIP in pipeline '%s': No Data Received", ctx.PipelineId())
}
ctx.LoggingClient().Debugf("Compression with GZIP in pipeline '%s'", ctx.PipelineId())
rawData, err := util.CoerceType(data)
if err != nil {
return false, err
}
var buf bytes.Buffer
if compression.gzipWriter == nil {
compression.gzipWriter = gzip.NewWriter(&buf)
} else {
compression.gzipWriter.Reset(&buf)
}
_, err = compression.gzipWriter.Write(rawData)
if err != nil {
return false, fmt.Errorf("unable to write GZIP data in pipeline '%s': %s", ctx.PipelineId(), err.Error())
}
err = compression.gzipWriter.Close()
if err != nil {
return false, fmt.Errorf("unable to close GZIP data in pipeline '%s': %s", ctx.PipelineId(), err.Error())
}
// Set response "content-type" header to "text/plain"
ctx.SetResponseContentType(common.ContentTypeText)
return true, bytesBufferToBase64(ctx.LoggingClient(), buf)
}
// CompressWithZLIB compresses data received as either a string,[]byte, or json.Marshaller using zlib algorithm
// and returns a base64 encoded string as a []byte.
func (compression *Compression) CompressWithZLIB(ctx interfaces.AppFunctionContext, data interface{}) (bool, interface{}) {
// as zlib writer is not allowed to be used by multiple goroutines, to avoid data race, use mutex lock to ensure atomic zlib writer operation.
compression.mutex.Lock()
defer compression.mutex.Unlock()
if data == nil {
// We didn't receive a result
return false, fmt.Errorf("function CompressWithZLIB in pipeline '%s': No Data Received", ctx.PipelineId())
}
ctx.LoggingClient().Debugf("Compression with ZLIB in pipeline '%s'", ctx.PipelineId())
byteData, err := util.CoerceType(data)
if err != nil {
return false, err
}
var buf bytes.Buffer
if compression.zlibWriter == nil {
compression.zlibWriter = zlib.NewWriter(&buf)
} else {
compression.zlibWriter.Reset(&buf)
}
_, err = compression.zlibWriter.Write(byteData)
if err != nil {
return false, fmt.Errorf("unable to write ZLIB data in pipeline '%s': %s", ctx.PipelineId(), err.Error())
}
err = compression.zlibWriter.Close()
if err != nil {
return false, fmt.Errorf("unable to close ZLIB data in pipeline '%s': %s", ctx.PipelineId(), err.Error())
}
// Set response "content-type" header to "text/plain"
ctx.SetResponseContentType(common.ContentTypeText)
return true, bytesBufferToBase64(ctx.LoggingClient(), buf)
}
func bytesBufferToBase64(lc logger.LoggingClient, buf bytes.Buffer) []byte {
lc.Debugf("Encoding compressed bytes of length %d vs %d", len(buf.Bytes()), buf.Len())
dst := make([]byte, base64.StdEncoding.EncodedLen(buf.Len()))
base64.StdEncoding.Encode(dst, buf.Bytes())
lc.Debugf("Encoding compressed bytes complete. New length is %d", len(dst))
return dst
}