1 files changed, 29 insertions, 36 deletions

diff --git a/modules/typesniffer/typesniffer.go b/modules/typesniffer/typesniffer.go
index 8cb3d278ce..2e8d9c4a1e 100644
--- a/modules/typesniffer/typesniffer.go
+++ b/modules/typesniffer/typesniffer.go
@@ -6,18 +6,14 @@ package typesniffer
 import (
 	"bytes"
 	"encoding/binary"
-	"fmt"
-	"io"
 	"net/http"
 	"regexp"
 	"slices"
 	"strings"
-
-	"code.gitea.io/gitea/modules/util"
+	"sync"
 )
 
-// Use at most this many bytes to determine Content Type.
-const sniffLen = 1024
+const SniffContentSize = 1024
 
 const (
 	MimeTypeImageSvg  = "image/svg+xml"
@@ -26,22 +22,30 @@ const (
 	MimeTypeApplicationOctetStream = "application/octet-stream"
 )
 
-var (
-	svgComment       = regexp.MustCompile(`(?s)<!--.*?-->`)
-	svgTagRegex      = regexp.MustCompile(`(?si)\A\s*(?:(<!DOCTYPE\s+svg([\s:]+.*?>|>))\s*)*<svg\b`)
-	svgTagInXMLRegex = regexp.MustCompile(`(?si)\A<\?xml\b.*?\?>\s*(?:(<!DOCTYPE\s+svg([\s:]+.*?>|>))\s*)*<svg\b`)
-)
-
-// SniffedType contains information about a blobs type.
+var globalVars = sync.OnceValue(func() (ret struct {
+	svgComment, svgTagRegex, svgTagInXMLRegex *regexp.Regexp
+},
+) {
+	ret.svgComment = regexp.MustCompile(`(?s)<!--.*?-->`)
+	ret.svgTagRegex = regexp.MustCompile(`(?si)\A\s*(?:(<!DOCTYPE\s+svg([\s:]+.*?>|>))\s*)*<svg\b`)
+	ret.svgTagInXMLRegex = regexp.MustCompile(`(?si)\A<\?xml\b.*?\?>\s*(?:(<!DOCTYPE\s+svg([\s:]+.*?>|>))\s*)*<svg\b`)
+	return ret
+})
+
+// SniffedType contains information about a blob's type.
 type SniffedType struct {
 	contentType string
 }
 
-// IsText etects if content format is plain text.
+// IsText detects if the content format is text family, including text/plain, text/html, text/css, etc.
 func (ct SniffedType) IsText() bool {
 	return strings.Contains(ct.contentType, "text/")
 }
 
+func (ct SniffedType) IsTextPlain() bool {
+	return strings.Contains(ct.contentType, "text/plain")
+}
+
 // IsImage detects if data is an image format
 func (ct SniffedType) IsImage() bool {
 	return strings.Contains(ct.contentType, "image/")
@@ -57,12 +61,12 @@ func (ct SniffedType) IsPDF() bool {
 	return strings.Contains(ct.contentType, "application/pdf")
 }
 
-// IsVideo detects if data is an video format
+// IsVideo detects if data is a video format
 func (ct SniffedType) IsVideo() bool {
 	return strings.Contains(ct.contentType, "video/")
 }
 
-// IsAudio detects if data is an video format
+// IsAudio detects if data is a video format
 func (ct SniffedType) IsAudio() bool {
 	return strings.Contains(ct.contentType, "audio/")
 }
@@ -103,33 +107,34 @@ func detectFileTypeBox(data []byte) (brands []string, found bool) {
 	return brands, true
 }
 
-// DetectContentType extends http.DetectContentType with more content types. Defaults to text/unknown if input is empty.
+// DetectContentType extends http.DetectContentType with more content types. Defaults to text/plain if input is empty.
 func DetectContentType(data []byte) SniffedType {
 	if len(data) == 0 {
-		return SniffedType{"text/unknown"}
+		return SniffedType{"text/plain"}
 	}
 
 	ct := http.DetectContentType(data)
 
-	if len(data) > sniffLen {
-		data = data[:sniffLen]
+	if len(data) > SniffContentSize {
+		data = data[:SniffContentSize]
 	}
 
+	vars := globalVars()
 	// SVG is unsupported by http.DetectContentType, https://github.com/golang/go/issues/15888
 	detectByHTML := strings.Contains(ct, "text/plain") || strings.Contains(ct, "text/html")
 	detectByXML := strings.Contains(ct, "text/xml")
 	if detectByHTML || detectByXML {
-		dataProcessed := svgComment.ReplaceAll(data, nil)
+		dataProcessed := vars.svgComment.ReplaceAll(data, nil)
 		dataProcessed = bytes.TrimSpace(dataProcessed)
-		if detectByHTML && svgTagRegex.Match(dataProcessed) ||
-			detectByXML && svgTagInXMLRegex.Match(dataProcessed) {
+		if detectByHTML && vars.svgTagRegex.Match(dataProcessed) ||
+			detectByXML && vars.svgTagInXMLRegex.Match(dataProcessed) {
 			ct = MimeTypeImageSvg
 		}
 	}
 
 	if strings.HasPrefix(ct, "audio/") && bytes.HasPrefix(data, []byte("ID3")) {
 		// The MP3 detection is quite inaccurate, any content with "ID3" prefix will result in "audio/mpeg".
-		// So remove the "ID3" prefix and detect again, if result is text, then it must be text content.
+		// So remove the "ID3" prefix and detect again, then if the result is "text", it must be text content.
 		// This works especially because audio files contain many unprintable/invalid characters like `0x00`
 		ct2 := http.DetectContentType(data[3:])
 		if strings.HasPrefix(ct2, "text/") {
@@ -155,15 +160,3 @@ func DetectContentType(data []byte) SniffedType {
 	}
 	return SniffedType{ct}
 }
-
-// DetectContentTypeFromReader guesses the content type contained in the reader.
-func DetectContentTypeFromReader(r io.Reader) (SniffedType, error) {
-	buf := make([]byte, sniffLen)
-	n, err := util.ReadAtMost(r, buf)
-	if err != nil {
-		return SniffedType{}, fmt.Errorf("DetectContentTypeFromReader io error: %w", err)
-	}
-	buf = buf[:n]
-
-	return DetectContentType(buf), nil
-}