Add a storage layer for attachments (#11387)

* Add a storage layer for attachments * Fix some bug * fix test * Fix copyright head and lint * Fix bug * Add setting for minio and flags for migrate-storage * Add documents * fix lint * Add test for minio store type on attachments * fix test * fix test * Apply suggestions from code review Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com> * Add warning when storage migrated successfully * Fix drone * fix test * rebase * Fix test * display the error on console * Move minio test to amd64 since minio docker don't support arm64 * refactor the codes * add trace * Fix test * remove log on xorm * Fi download bug * Add a storage layer for attachments * Add setting for minio and flags for migrate-storage * fix lint * Add test for minio store type on attachments * Apply suggestions from code review Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com> * Fix drone * fix test * Fix test * display the error on console * Move minio test to amd64 since minio docker don't support arm64 * refactor the codes * add trace * Fix test * Add URL function to serve attachments directly from S3/Minio * Add ability to enable/disable redirection in attachment configuration * Fix typo * Add a storage layer for attachments * Add setting for minio and flags for migrate-storage * fix lint * Add test for minio store type on attachments * Apply suggestions from code review Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com> * Fix drone * fix test * Fix test * display the error on console * Move minio test to amd64 since minio docker don't support arm64 * don't change unrelated files * Fix lint * Fix build * update go.mod and go.sum * Use github.com/minio/minio-go/v6 * Remove unused function * Upgrade minio to v7 and some other improvements * fix lint * Fix go mod Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com> Co-authored-by: Tyler <tystuyfzand@gmail.com>
2020-08-18 12:23:45 +08:00 · 2020-08-18 12:23:45 +08:00 · 62e6c9bc6c
commit 62e6c9bc6c
parent 02fbe1e5dc
330 changed files with 62099 additions and 331 deletions
--- a/vendor/github.com/minio/minio-go/v7/api-select.go
+++ b/vendor/github.com/minio/minio-go/v7/api-select.go
@ -0,0 +1,751 @@
+/*
+ * MinIO Go Library for Amazon S3 Compatible Cloud Storage
+ * (C) 2018-2020 MinIO, Inc.
+ *
+ * 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 minio
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"hash"
+	"hash/crc32"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/minio/minio-go/v7/pkg/encrypt"
+	"github.com/minio/minio-go/v7/pkg/s3utils"
+)
+
+// CSVFileHeaderInfo - is the parameter for whether to utilize headers.
+type CSVFileHeaderInfo string
+
+// Constants for file header info.
+const (
+	CSVFileHeaderInfoNone   CSVFileHeaderInfo = "NONE"
+	CSVFileHeaderInfoIgnore                   = "IGNORE"
+	CSVFileHeaderInfoUse                      = "USE"
+)
+
+// SelectCompressionType - is the parameter for what type of compression is
+// present
+type SelectCompressionType string
+
+// Constants for compression types under select API.
+const (
+	SelectCompressionNONE SelectCompressionType = "NONE"
+	SelectCompressionGZIP                       = "GZIP"
+	SelectCompressionBZIP                       = "BZIP2"
+)
+
+// CSVQuoteFields - is the parameter for how CSV fields are quoted.
+type CSVQuoteFields string
+
+// Constants for csv quote styles.
+const (
+	CSVQuoteFieldsAlways   CSVQuoteFields = "Always"
+	CSVQuoteFieldsAsNeeded                = "AsNeeded"
+)
+
+// QueryExpressionType - is of what syntax the expression is, this should only
+// be SQL
+type QueryExpressionType string
+
+// Constants for expression type.
+const (
+	QueryExpressionTypeSQL QueryExpressionType = "SQL"
+)
+
+// JSONType determines json input serialization type.
+type JSONType string
+
+// Constants for JSONTypes.
+const (
+	JSONDocumentType JSONType = "DOCUMENT"
+	JSONLinesType             = "LINES"
+)
+
+// ParquetInputOptions parquet input specific options
+type ParquetInputOptions struct{}
+
+// CSVInputOptions csv input specific options
+type CSVInputOptions struct {
+	FileHeaderInfo    CSVFileHeaderInfo
+	fileHeaderInfoSet bool
+
+	RecordDelimiter    string
+	recordDelimiterSet bool
+
+	FieldDelimiter    string
+	fieldDelimiterSet bool
+
+	QuoteCharacter    string
+	quoteCharacterSet bool
+
+	QuoteEscapeCharacter    string
+	quoteEscapeCharacterSet bool
+
+	Comments    string
+	commentsSet bool
+}
+
+// SetFileHeaderInfo sets the file header info in the CSV input options
+func (c *CSVInputOptions) SetFileHeaderInfo(val CSVFileHeaderInfo) {
+	c.FileHeaderInfo = val
+	c.fileHeaderInfoSet = true
+}
+
+// SetRecordDelimiter sets the record delimiter in the CSV input options
+func (c *CSVInputOptions) SetRecordDelimiter(val string) {
+	c.RecordDelimiter = val
+	c.recordDelimiterSet = true
+}
+
+// SetFieldDelimiter sets the field delimiter in the CSV input options
+func (c *CSVInputOptions) SetFieldDelimiter(val string) {
+	c.FieldDelimiter = val
+	c.fieldDelimiterSet = true
+}
+
+// SetQuoteCharacter sets the quote character in the CSV input options
+func (c *CSVInputOptions) SetQuoteCharacter(val string) {
+	c.QuoteCharacter = val
+	c.quoteCharacterSet = true
+}
+
+// SetQuoteEscapeCharacter sets the quote escape character in the CSV input options
+func (c *CSVInputOptions) SetQuoteEscapeCharacter(val string) {
+	c.QuoteEscapeCharacter = val
+	c.quoteEscapeCharacterSet = true
+}
+
+// SetComments sets the comments character in the CSV input options
+func (c *CSVInputOptions) SetComments(val string) {
+	c.Comments = val
+	c.commentsSet = true
+}
+
+// MarshalXML - produces the xml representation of the CSV input options struct
+func (c CSVInputOptions) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	if err := e.EncodeToken(start); err != nil {
+		return err
+	}
+	if c.FileHeaderInfo != "" || c.fileHeaderInfoSet {
+		if err := e.EncodeElement(c.FileHeaderInfo, xml.StartElement{Name: xml.Name{Local: "FileHeaderInfo"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.RecordDelimiter != "" || c.recordDelimiterSet {
+		if err := e.EncodeElement(c.RecordDelimiter, xml.StartElement{Name: xml.Name{Local: "RecordDelimiter"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.FieldDelimiter != "" || c.fieldDelimiterSet {
+		if err := e.EncodeElement(c.FieldDelimiter, xml.StartElement{Name: xml.Name{Local: "FieldDelimiter"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.QuoteCharacter != "" || c.quoteCharacterSet {
+		if err := e.EncodeElement(c.QuoteCharacter, xml.StartElement{Name: xml.Name{Local: "QuoteCharacter"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.QuoteEscapeCharacter != "" || c.quoteEscapeCharacterSet {
+		if err := e.EncodeElement(c.QuoteEscapeCharacter, xml.StartElement{Name: xml.Name{Local: "QuoteEscapeCharacter"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.Comments != "" || c.commentsSet {
+		if err := e.EncodeElement(c.Comments, xml.StartElement{Name: xml.Name{Local: "Comments"}}); err != nil {
+			return err
+		}
+	}
+
+	return e.EncodeToken(xml.EndElement{Name: start.Name})
+}
+
+// CSVOutputOptions csv output specific options
+type CSVOutputOptions struct {
+	QuoteFields    CSVQuoteFields
+	quoteFieldsSet bool
+
+	RecordDelimiter    string
+	recordDelimiterSet bool
+
+	FieldDelimiter    string
+	fieldDelimiterSet bool
+
+	QuoteCharacter    string
+	quoteCharacterSet bool
+
+	QuoteEscapeCharacter    string
+	quoteEscapeCharacterSet bool
+}
+
+// SetQuoteFields sets the quote field parameter in the CSV output options
+func (c *CSVOutputOptions) SetQuoteFields(val CSVQuoteFields) {
+	c.QuoteFields = val
+	c.quoteFieldsSet = true
+}
+
+// SetRecordDelimiter sets the record delimiter character in the CSV output options
+func (c *CSVOutputOptions) SetRecordDelimiter(val string) {
+	c.RecordDelimiter = val
+	c.recordDelimiterSet = true
+}
+
+// SetFieldDelimiter sets the field delimiter character in the CSV output options
+func (c *CSVOutputOptions) SetFieldDelimiter(val string) {
+	c.FieldDelimiter = val
+	c.fieldDelimiterSet = true
+}
+
+// SetQuoteCharacter sets the quote character in the CSV output options
+func (c *CSVOutputOptions) SetQuoteCharacter(val string) {
+	c.QuoteCharacter = val
+	c.quoteCharacterSet = true
+}
+
+// SetQuoteEscapeCharacter sets the quote escape character in the CSV output options
+func (c *CSVOutputOptions) SetQuoteEscapeCharacter(val string) {
+	c.QuoteEscapeCharacter = val
+	c.quoteEscapeCharacterSet = true
+}
+
+// MarshalXML - produces the xml representation of the CSVOutputOptions struct
+func (c CSVOutputOptions) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	if err := e.EncodeToken(start); err != nil {
+		return err
+	}
+
+	if c.QuoteFields != "" || c.quoteFieldsSet {
+		if err := e.EncodeElement(c.QuoteFields, xml.StartElement{Name: xml.Name{Local: "QuoteFields"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.RecordDelimiter != "" || c.recordDelimiterSet {
+		if err := e.EncodeElement(c.RecordDelimiter, xml.StartElement{Name: xml.Name{Local: "RecordDelimiter"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.FieldDelimiter != "" || c.fieldDelimiterSet {
+		if err := e.EncodeElement(c.FieldDelimiter, xml.StartElement{Name: xml.Name{Local: "FieldDelimiter"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.QuoteCharacter != "" || c.quoteCharacterSet {
+		if err := e.EncodeElement(c.QuoteCharacter, xml.StartElement{Name: xml.Name{Local: "QuoteCharacter"}}); err != nil {
+			return err
+		}
+	}
+
+	if c.QuoteEscapeCharacter != "" || c.quoteEscapeCharacterSet {
+		if err := e.EncodeElement(c.QuoteEscapeCharacter, xml.StartElement{Name: xml.Name{Local: "QuoteEscapeCharacter"}}); err != nil {
+			return err
+		}
+	}
+
+	return e.EncodeToken(xml.EndElement{Name: start.Name})
+}
+
+// JSONInputOptions json input specific options
+type JSONInputOptions struct {
+	Type    JSONType
+	typeSet bool
+}
+
+// SetType sets the JSON type in the JSON input options
+func (j *JSONInputOptions) SetType(typ JSONType) {
+	j.Type = typ
+	j.typeSet = true
+}
+
+// MarshalXML - produces the xml representation of the JSONInputOptions struct
+func (j JSONInputOptions) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	if err := e.EncodeToken(start); err != nil {
+		return err
+	}
+
+	if j.Type != "" || j.typeSet {
+		if err := e.EncodeElement(j.Type, xml.StartElement{Name: xml.Name{Local: "Type"}}); err != nil {
+			return err
+		}
+	}
+
+	return e.EncodeToken(xml.EndElement{Name: start.Name})
+}
+
+// JSONOutputOptions - json output specific options
+type JSONOutputOptions struct {
+	RecordDelimiter    string
+	recordDelimiterSet bool
+}
+
+// SetRecordDelimiter sets the record delimiter in the JSON output options
+func (j *JSONOutputOptions) SetRecordDelimiter(val string) {
+	j.RecordDelimiter = val
+	j.recordDelimiterSet = true
+}
+
+// MarshalXML - produces the xml representation of the JSONOutputOptions struct
+func (j JSONOutputOptions) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	if err := e.EncodeToken(start); err != nil {
+		return err
+	}
+
+	if j.RecordDelimiter != "" || j.recordDelimiterSet {
+		if err := e.EncodeElement(j.RecordDelimiter, xml.StartElement{Name: xml.Name{Local: "RecordDelimiter"}}); err != nil {
+			return err
+		}
+	}
+
+	return e.EncodeToken(xml.EndElement{Name: start.Name})
+}
+
+// SelectObjectInputSerialization - input serialization parameters
+type SelectObjectInputSerialization struct {
+	CompressionType SelectCompressionType
+	Parquet         *ParquetInputOptions `xml:"Parquet,omitempty"`
+	CSV             *CSVInputOptions     `xml:"CSV,omitempty"`
+	JSON            *JSONInputOptions    `xml:"JSON,omitempty"`
+}
+
+// SelectObjectOutputSerialization - output serialization parameters.
+type SelectObjectOutputSerialization struct {
+	CSV  *CSVOutputOptions  `xml:"CSV,omitempty"`
+	JSON *JSONOutputOptions `xml:"JSON,omitempty"`
+}
+
+// SelectObjectOptions - represents the input select body
+type SelectObjectOptions struct {
+	XMLName              xml.Name           `xml:"SelectObjectContentRequest" json:"-"`
+	ServerSideEncryption encrypt.ServerSide `xml:"-"`
+	Expression           string
+	ExpressionType       QueryExpressionType
+	InputSerialization   SelectObjectInputSerialization
+	OutputSerialization  SelectObjectOutputSerialization
+	RequestProgress      struct {
+		Enabled bool
+	}
+}
+
+// Header returns the http.Header representation of the SelectObject options.
+func (o SelectObjectOptions) Header() http.Header {
+	headers := make(http.Header)
+	if o.ServerSideEncryption != nil && o.ServerSideEncryption.Type() == encrypt.SSEC {
+		o.ServerSideEncryption.Marshal(headers)
+	}
+	return headers
+}
+
+// SelectObjectType - is the parameter which defines what type of object the
+// operation is being performed on.
+type SelectObjectType string
+
+// Constants for input data types.
+const (
+	SelectObjectTypeCSV     SelectObjectType = "CSV"
+	SelectObjectTypeJSON                     = "JSON"
+	SelectObjectTypeParquet                  = "Parquet"
+)
+
+// preludeInfo is used for keeping track of necessary information from the
+// prelude.
+type preludeInfo struct {
+	totalLen  uint32
+	headerLen uint32
+}
+
+// SelectResults is used for the streaming responses from the server.
+type SelectResults struct {
+	pipeReader *io.PipeReader
+	resp       *http.Response
+	stats      *StatsMessage
+	progress   *ProgressMessage
+}
+
+// ProgressMessage is a struct for progress xml message.
+type ProgressMessage struct {
+	XMLName xml.Name `xml:"Progress" json:"-"`
+	StatsMessage
+}
+
+// StatsMessage is a struct for stat xml message.
+type StatsMessage struct {
+	XMLName        xml.Name `xml:"Stats" json:"-"`
+	BytesScanned   int64
+	BytesProcessed int64
+	BytesReturned  int64
+}
+
+// messageType represents the type of message.
+type messageType string
+
+const (
+	errorMsg  messageType = "error"
+	commonMsg             = "event"
+)
+
+// eventType represents the type of event.
+type eventType string
+
+// list of event-types returned by Select API.
+const (
+	endEvent      eventType = "End"
+	recordsEvent            = "Records"
+	progressEvent           = "Progress"
+	statsEvent              = "Stats"
+)
+
+// contentType represents content type of event.
+type contentType string
+
+const (
+	xmlContent contentType = "text/xml"
+)
+
+// SelectObjectContent is a implementation of http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectSELECTContent.html AWS S3 API.
+func (c Client) SelectObjectContent(ctx context.Context, bucketName, objectName string, opts SelectObjectOptions) (*SelectResults, error) {
+	// Input validation.
+	if err := s3utils.CheckValidBucketName(bucketName); err != nil {
+		return nil, err
+	}
+	if err := s3utils.CheckValidObjectName(objectName); err != nil {
+		return nil, err
+	}
+
+	selectReqBytes, err := xml.Marshal(opts)
+	if err != nil {
+		return nil, err
+	}
+
+	urlValues := make(url.Values)
+	urlValues.Set("select", "")
+	urlValues.Set("select-type", "2")
+
+	// Execute POST on bucket/object.
+	resp, err := c.executeMethod(ctx, http.MethodPost, requestMetadata{
+		bucketName:       bucketName,
+		objectName:       objectName,
+		queryValues:      urlValues,
+		customHeader:     opts.Header(),
+		contentMD5Base64: sumMD5Base64(selectReqBytes),
+		contentSHA256Hex: sum256Hex(selectReqBytes),
+		contentBody:      bytes.NewReader(selectReqBytes),
+		contentLength:    int64(len(selectReqBytes)),
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return NewSelectResults(resp, bucketName)
+}
+
+// NewSelectResults creates a Select Result parser that parses the response
+// and returns a Reader that will return parsed and assembled select output.
+func NewSelectResults(resp *http.Response, bucketName string) (*SelectResults, error) {
+	if resp.StatusCode != http.StatusOK {
+		return nil, httpRespToErrorResponse(resp, bucketName, "")
+	}
+
+	pipeReader, pipeWriter := io.Pipe()
+	streamer := &SelectResults{
+		resp:       resp,
+		stats:      &StatsMessage{},
+		progress:   &ProgressMessage{},
+		pipeReader: pipeReader,
+	}
+	streamer.start(pipeWriter)
+	return streamer, nil
+}
+
+// Close - closes the underlying response body and the stream reader.
+func (s *SelectResults) Close() error {
+	defer closeResponse(s.resp)
+	return s.pipeReader.Close()
+}
+
+// Read - is a reader compatible implementation for SelectObjectContent records.
+func (s *SelectResults) Read(b []byte) (n int, err error) {
+	return s.pipeReader.Read(b)
+}
+
+// Stats - information about a request's stats when processing is complete.
+func (s *SelectResults) Stats() *StatsMessage {
+	return s.stats
+}
+
+// Progress - information about the progress of a request.
+func (s *SelectResults) Progress() *ProgressMessage {
+	return s.progress
+}
+
+// start is the main function that decodes the large byte array into
+// several events that are sent through the eventstream.
+func (s *SelectResults) start(pipeWriter *io.PipeWriter) {
+	go func() {
+		for {
+			var prelude preludeInfo
+			var headers = make(http.Header)
+			var err error
+
+			// Create CRC code
+			crc := crc32.New(crc32.IEEETable)
+			crcReader := io.TeeReader(s.resp.Body, crc)
+
+			// Extract the prelude(12 bytes) into a struct to extract relevant information.
+			prelude, err = processPrelude(crcReader, crc)
+			if err != nil {
+				pipeWriter.CloseWithError(err)
+				closeResponse(s.resp)
+				return
+			}
+
+			// Extract the headers(variable bytes) into a struct to extract relevant information
+			if prelude.headerLen > 0 {
+				if err = extractHeader(io.LimitReader(crcReader, int64(prelude.headerLen)), headers); err != nil {
+					pipeWriter.CloseWithError(err)
+					closeResponse(s.resp)
+					return
+				}
+			}
+
+			// Get the actual payload length so that the appropriate amount of
+			// bytes can be read or parsed.
+			payloadLen := prelude.PayloadLen()
+
+			m := messageType(headers.Get("message-type"))
+
+			switch m {
+			case errorMsg:
+				pipeWriter.CloseWithError(errors.New(headers.Get("error-code") + ":\"" + headers.Get("error-message") + "\""))
+				closeResponse(s.resp)
+				return
+			case commonMsg:
+				// Get content-type of the payload.
+				c := contentType(headers.Get("content-type"))
+
+				// Get event type of the payload.
+				e := eventType(headers.Get("event-type"))
+
+				// Handle all supported events.
+				switch e {
+				case endEvent:
+					pipeWriter.Close()
+					closeResponse(s.resp)
+					return
+				case recordsEvent:
+					if _, err = io.Copy(pipeWriter, io.LimitReader(crcReader, payloadLen)); err != nil {
+						pipeWriter.CloseWithError(err)
+						closeResponse(s.resp)
+						return
+					}
+				case progressEvent:
+					switch c {
+					case xmlContent:
+						if err = xmlDecoder(io.LimitReader(crcReader, payloadLen), s.progress); err != nil {
+							pipeWriter.CloseWithError(err)
+							closeResponse(s.resp)
+							return
+						}
+					default:
+						pipeWriter.CloseWithError(fmt.Errorf("Unexpected content-type %s sent for event-type %s", c, progressEvent))
+						closeResponse(s.resp)
+						return
+					}
+				case statsEvent:
+					switch c {
+					case xmlContent:
+						if err = xmlDecoder(io.LimitReader(crcReader, payloadLen), s.stats); err != nil {
+							pipeWriter.CloseWithError(err)
+							closeResponse(s.resp)
+							return
+						}
+					default:
+						pipeWriter.CloseWithError(fmt.Errorf("Unexpected content-type %s sent for event-type %s", c, statsEvent))
+						closeResponse(s.resp)
+						return
+					}
+				}
+			}
+
+			// Ensures that the full message's CRC is correct and
+			// that the message is not corrupted
+			if err := checkCRC(s.resp.Body, crc.Sum32()); err != nil {
+				pipeWriter.CloseWithError(err)
+				closeResponse(s.resp)
+				return
+			}
+
+		}
+	}()
+}
+
+// PayloadLen is a function that calculates the length of the payload.
+func (p preludeInfo) PayloadLen() int64 {
+	return int64(p.totalLen - p.headerLen - 16)
+}
+
+// processPrelude is the function that reads the 12 bytes of the prelude and
+// ensures the CRC is correct while also extracting relevant information into
+// the struct,
+func processPrelude(prelude io.Reader, crc hash.Hash32) (preludeInfo, error) {
+	var err error
+	var pInfo = preludeInfo{}
+
+	// reads total length of the message (first 4 bytes)
+	pInfo.totalLen, err = extractUint32(prelude)
+	if err != nil {
+		return pInfo, err
+	}
+
+	// reads total header length of the message (2nd 4 bytes)
+	pInfo.headerLen, err = extractUint32(prelude)
+	if err != nil {
+		return pInfo, err
+	}
+
+	// checks that the CRC is correct (3rd 4 bytes)
+	preCRC := crc.Sum32()
+	if err := checkCRC(prelude, preCRC); err != nil {
+		return pInfo, err
+	}
+
+	return pInfo, nil
+}
+
+// extracts the relevant information from the Headers.
+func extractHeader(body io.Reader, myHeaders http.Header) error {
+	for {
+		// extracts the first part of the header,
+		headerTypeName, err := extractHeaderType(body)
+		if err != nil {
+			// Since end of file, we have read all of our headers
+			if err == io.EOF {
+				break
+			}
+			return err
+		}
+
+		// reads the 7 present in the header and ignores it.
+		extractUint8(body)
+
+		headerValueName, err := extractHeaderValue(body)
+		if err != nil {
+			return err
+		}
+
+		myHeaders.Set(headerTypeName, headerValueName)
+
+	}
+	return nil
+}
+
+// extractHeaderType extracts the first half of the header message, the header type.
+func extractHeaderType(body io.Reader) (string, error) {
+	// extracts 2 bit integer
+	headerNameLen, err := extractUint8(body)
+	if err != nil {
+		return "", err
+	}
+	// extracts the string with the appropriate number of bytes
+	headerName, err := extractString(body, int(headerNameLen))
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimPrefix(headerName, ":"), nil
+}
+
+// extractsHeaderValue extracts the second half of the header message, the
+// header value
+func extractHeaderValue(body io.Reader) (string, error) {
+	bodyLen, err := extractUint16(body)
+	if err != nil {
+		return "", err
+	}
+	bodyName, err := extractString(body, int(bodyLen))
+	if err != nil {
+		return "", err
+	}
+	return bodyName, nil
+}
+
+// extracts a string from byte array of a particular number of bytes.
+func extractString(source io.Reader, lenBytes int) (string, error) {
+	myVal := make([]byte, lenBytes)
+	_, err := source.Read(myVal)
+	if err != nil {
+		return "", err
+	}
+	return string(myVal), nil
+}
+
+// extractUint32 extracts a 4 byte integer from the byte array.
+func extractUint32(r io.Reader) (uint32, error) {
+	buf := make([]byte, 4)
+	_, err := readFull(r, buf)
+	if err != nil {
+		return 0, err
+	}
+	return binary.BigEndian.Uint32(buf), nil
+}
+
+// extractUint16 extracts a 2 byte integer from the byte array.
+func extractUint16(r io.Reader) (uint16, error) {
+	buf := make([]byte, 2)
+	_, err := readFull(r, buf)
+	if err != nil {
+		return 0, err
+	}
+	return binary.BigEndian.Uint16(buf), nil
+}
+
+// extractUint8 extracts a 1 byte integer from the byte array.
+func extractUint8(r io.Reader) (uint8, error) {
+	buf := make([]byte, 1)
+	_, err := readFull(r, buf)
+	if err != nil {
+		return 0, err
+	}
+	return buf[0], nil
+}
+
+// checkCRC ensures that the CRC matches with the one from the reader.
+func checkCRC(r io.Reader, expect uint32) error {
+	msgCRC, err := extractUint32(r)
+	if err != nil {
+		return err
+	}
+
+	if msgCRC != expect {
+		return fmt.Errorf("Checksum Mismatch, MessageCRC of 0x%X does not equal expected CRC of 0x%X", msgCRC, expect)
+
+	}
+	return nil
+}