syntax parser: reintroduce header regex in .hdr files

Replacing header patterns with signature patterns was a mistake, since
both have their own uses. So restore support for header regex, while
keeping support for signature regex as well.

pkg/highlight/parser.go

@@ -39,6 +39,7 @@ type Def struct {
 type Header struct {
 	FileType       string
 	FileNameRegex  *regexp.Regexp
+	HeaderRegex    *regexp.Regexp
 	SignatureRegex *regexp.Regexp
 }
 
@@ -46,6 +47,7 @@ type HeaderYaml struct {
 	FileType string `yaml:"filetype"`
 	Detect   struct {
 		FNameRegexStr     string `yaml:"filename"`
+		HeaderRegexStr    string `yaml:"header"`
 		SignatureRegexStr string `yaml:"signature"`
 	} `yaml:"detect"`
 }
@@ -96,18 +98,22 @@ func init() {
 // A yaml file might take ~400us to parse while a header file only takes ~20us
 func MakeHeader(data []byte) (*Header, error) {
 	lines := bytes.Split(data, []byte{'\n'})
-	if len(lines) < 3 {
+	if len(lines) < 4 {
 		return nil, errors.New("Header file has incorrect format")
 	}
 	header := new(Header)
 	var err error
 	header.FileType = string(lines[0])
 	fnameRegexStr := string(lines[1])
-	signatureRegexStr := string(lines[2])
+	headerRegexStr := string(lines[2])
+	signatureRegexStr := string(lines[3])
 
 	if fnameRegexStr != "" {
 		header.FileNameRegex, err = regexp.Compile(fnameRegexStr)
 	}
+	if err == nil && headerRegexStr != "" {
+		header.HeaderRegex, err = regexp.Compile(headerRegexStr)
+	}
 	if err == nil && signatureRegexStr != "" {
 		header.SignatureRegex, err = regexp.Compile(signatureRegexStr)
 	}
@@ -134,6 +140,9 @@ func MakeHeaderYaml(data []byte) (*Header, error) {
 	if hdrYaml.Detect.FNameRegexStr != "" {
 		header.FileNameRegex, err = regexp.Compile(hdrYaml.Detect.FNameRegexStr)
 	}
+	if err == nil && hdrYaml.Detect.HeaderRegexStr != "" {
+		header.HeaderRegex, err = regexp.Compile(hdrYaml.Detect.HeaderRegexStr)
+	}
 	if err == nil && hdrYaml.Detect.SignatureRegexStr != "" {
 		header.SignatureRegex, err = regexp.Compile(hdrYaml.Detect.SignatureRegexStr)
 	}
@@ -154,6 +163,14 @@ func (header *Header) MatchFileName(filename string) bool {
 	return false
 }
 
+func (header *Header) MatchFileHeader(firstLine []byte) bool {
+	if header.HeaderRegex != nil {
+		return header.HeaderRegex.Match(firstLine)
+	}
+
+	return false
+}
+
 // HasFileSignature checks the presence of a stored signature
 func (header *Header) HasFileSignature() bool {
 	return header.SignatureRegex != nil

runtime/syntax/make_headers.go

@@ -18,6 +18,7 @@ type HeaderYaml struct {
 	FileType string `yaml:"filetype"`
 	Detect   struct {
 		FNameRgx     string `yaml:"filename"`
+		HeaderRgx    string `yaml:"header"`
 		SignatureRgx string `yaml:"signature"`
 	} `yaml:"detect"`
 }
@@ -25,6 +26,7 @@ type HeaderYaml struct {
 type Header struct {
 	FileType     string
 	FNameRgx     string
+	HeaderRgx    string
 	SignatureRgx string
 }
 
@@ -59,6 +61,7 @@ func encode(name string, c HeaderYaml) {
 	f, _ := os.Create(name + ".hdr")
 	f.WriteString(c.FileType + "\n")
 	f.WriteString(c.Detect.FNameRgx + "\n")
+	f.WriteString(c.Detect.HeaderRgx + "\n")
 	f.WriteString(c.Detect.SignatureRgx + "\n")
 	f.Close()
 }
@@ -70,7 +73,8 @@ func decode(name string) Header {
 	var hdr Header
 	hdr.FileType = string(strs[0])
 	hdr.FNameRgx = string(strs[1])
-	hdr.SignatureRgx = string(strs[2])
+	hdr.HeaderRgx = string(strs[2])
+	hdr.SignatureRgx = string(strs[3])
 	fmt.Printf("took %v\n", time.Since(start))
 
 	return hdr