GODRIVER-3303 Remove redundant code; Add test cases.

mongo/integration/mtest/wiremessage_helpers.go

@@ -49,16 +49,11 @@ func parseOpCompressed(wm []byte) (wiremessage.OpCode, []byte, error) {
 		return originalOpcode, nil, errors.New("failed to read uncompressed size")
 	}
 
-	compressorID, wm, ok := wiremessage.ReadCompressedCompressorID(wm)
+	compressorID, compressedMsg, ok := wiremessage.ReadCompressedCompressorID(wm)
 	if !ok {
 		return originalOpcode, nil, errors.New("failed to read compressor ID")
 	}
 
-	compressedMsg, _, ok := wiremessage.ReadCompressedCompressedMessage(wm, int32(len(wm)))
-	if !ok {
-		return originalOpcode, nil, errors.New("failed to read compressed message")
-	}
-
 	opts := driver.CompressionOpts{
 		Compressor:       compressorID,
 		UncompressedSize: uncompressedSize,

x/mongo/driver/operation.go

@@ -1199,18 +1199,12 @@ func (Operation) decompressWireMessage(wm []byte) (wiremessage.OpCode, []byte, e
 	if !ok {
 		return 0, nil, errors.New("malformed OP_COMPRESSED: missing compressor ID")
 	}
-	compressedSize := len(wm) - 9 // original opcode (4) + uncompressed size (4) + compressor ID (1)
-	// return the original wiremessage
-	msg, _, ok := wiremessage.ReadCompressedCompressedMessage(rem, int32(compressedSize))
-	if !ok {
-		return 0, nil, errors.New("malformed OP_COMPRESSED: insufficient bytes for compressed wiremessage")
-	}
 
 	opts := CompressionOpts{
 		Compressor:       compressorID,
 		UncompressedSize: uncompressedSize,
 	}
-	uncompressed, err := DecompressPayload(msg, opts)
+	uncompressed, err := DecompressPayload(rem, opts)
 	if err != nil {
 		return 0, nil, err
 	}

x/mongo/driver/wiremessage/wiremessage.go

@@ -381,16 +381,9 @@ func ReadMsgSectionSingleDocument(src []byte) (doc bsoncore.Document, rem []byte
 // ReadMsgSectionDocumentSequence reads an identifier and document sequence from src and returns the document sequence
 // data parsed into a slice of BSON documents.
 func ReadMsgSectionDocumentSequence(src []byte) (identifier string, docs []bsoncore.Document, rem []byte, ok bool) {
-	length, rem, ok := readi32(src)
-	if !ok || int(length) > len(src) || length-4 < 0 {
-		return "", nil, rem, false
-	}
-
-	rem, ret := rem[:length-4], rem[length-4:] // reslice so we can just iterate a loop later
-
-	identifier, rem, ok = readcstring(rem)
+	identifier, rem, ret, ok := ReadMsgSectionRawDocumentSequence(src)
 	if !ok {
-		return "", nil, rem, false
+		return "", nil, src, false
 	}
 
 	docs = make([]bsoncore.Document, 0)
@@ -403,7 +396,7 @@ func ReadMsgSectionDocumentSequence(src []byte) (identifier string, docs []bsonc
 		docs = append(docs, doc)
 	}
 	if len(rem) > 0 {
-		return "", nil, append(rem, ret...), false
+		return "", nil, src, false
 	}
 
 	return identifier, docs, ret, true
@@ -414,7 +407,7 @@ func ReadMsgSectionDocumentSequence(src []byte) (identifier string, docs []bsonc
 func ReadMsgSectionRawDocumentSequence(src []byte) (identifier string, data []byte, rem []byte, ok bool) {
 	length, rem, ok := readi32(src)
 	if !ok || int(length) > len(src) || length-4 < 0 {
-		return "", nil, rem, false
+		return "", nil, src, false
 	}
 
 	// After these assignments, rem will be the data containing the identifier string + the document sequence bytes and
@@ -423,7 +416,7 @@ func ReadMsgSectionRawDocumentSequence(src []byte) (identifier string, data []by
 
 	identifier, rem, ok = readcstring(rem)
 	if !ok {
-		return "", nil, rem, false
+		return "", nil, src, false
 	}
 
 	return identifier, rem, rest, true
@@ -546,14 +539,6 @@ func ReadCompressedCompressorID(src []byte) (id CompressorID, rem []byte, ok boo
 	return CompressorID(src[0]), src[1:], true
 }
 
-// ReadCompressedCompressedMessage reads the compressed wiremessage to dst.
-func ReadCompressedCompressedMessage(src []byte, length int32) (msg []byte, rem []byte, ok bool) {
-	if len(src) < int(length) || length < 0 {
-		return nil, src, false
-	}
-	return src[:length], src[length:], true
-}
-
 // ReadKillCursorsZero reads the zero field from src.
 func ReadKillCursorsZero(src []byte) (zero int32, rem []byte, ok bool) {
 	return readi32(src)

x/mongo/driver/wiremessage/wiremessage_test.go

@@ -175,6 +175,22 @@ func TestReadMsgSectionDocumentSequence(t *testing.T) {
 			wantRem:        []byte{0, 1},
 			wantOK:         false,
 		},
+		{
+			desc:           "incorrect size",
+			src:            []byte{3, 0, 0},
+			wantIdentifier: "",
+			wantDocs:       nil,
+			wantRem:        []byte{3, 0, 0},
+			wantOK:         false,
+		},
+		{
+			desc:           "insufficient size",
+			src:            []byte{4, 0, 0},
+			wantIdentifier: "",
+			wantDocs:       nil,
+			wantRem:        []byte{4, 0, 0},
+			wantOK:         false,
+		},
 		{
 			desc:           "nil",
 			src:            nil,