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- // Copyright 2021 The Gitea Authors. All rights reserved.
- // SPDX-License-Identifier: MIT
-
- package typesniffer
-
- import (
- "bytes"
- "fmt"
- "io"
- "net/http"
- "regexp"
- "strings"
-
- "code.gitea.io/gitea/modules/util"
- )
-
- // Use at most this many bytes to determine Content Type.
- const sniffLen = 1024
-
- const (
- // SvgMimeType MIME type of SVG images.
- SvgMimeType = "image/svg+xml"
- // ApplicationOctetStream MIME type of binary files.
- ApplicationOctetStream = "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.
- type SniffedType struct {
- contentType string
- }
-
- // IsText etects if content format is plain text.
- func (ct SniffedType) IsText() bool {
- return strings.Contains(ct.contentType, "text/")
- }
-
- // IsImage detects if data is an image format
- func (ct SniffedType) IsImage() bool {
- return strings.Contains(ct.contentType, "image/")
- }
-
- // IsSvgImage detects if data is an SVG image format
- func (ct SniffedType) IsSvgImage() bool {
- return strings.Contains(ct.contentType, SvgMimeType)
- }
-
- // IsPDF detects if data is a PDF format
- func (ct SniffedType) IsPDF() bool {
- return strings.Contains(ct.contentType, "application/pdf")
- }
-
- // IsVideo detects if data is an video format
- func (ct SniffedType) IsVideo() bool {
- return strings.Contains(ct.contentType, "video/")
- }
-
- // IsAudio detects if data is an video format
- func (ct SniffedType) IsAudio() bool {
- return strings.Contains(ct.contentType, "audio/")
- }
-
- // IsRepresentableAsText returns true if file content can be represented as
- // plain text or is empty.
- func (ct SniffedType) IsRepresentableAsText() bool {
- return ct.IsText() || ct.IsSvgImage()
- }
-
- // IsBrowsableBinaryType returns whether a non-text type can be displayed in a browser
- func (ct SniffedType) IsBrowsableBinaryType() bool {
- return ct.IsImage() || ct.IsSvgImage() || ct.IsPDF() || ct.IsVideo() || ct.IsAudio()
- }
-
- // GetMimeType returns the mime type
- func (ct SniffedType) GetMimeType() string {
- return strings.SplitN(ct.contentType, ";", 2)[0]
- }
-
- // DetectContentType extends http.DetectContentType with more content types. Defaults to text/unknown if input is empty.
- func DetectContentType(data []byte) SniffedType {
- if len(data) == 0 {
- return SniffedType{"text/unknown"}
- }
-
- ct := http.DetectContentType(data)
-
- if len(data) > sniffLen {
- data = data[:sniffLen]
- }
-
- // 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 = bytes.TrimSpace(dataProcessed)
- if detectByHTML && svgTagRegex.Match(dataProcessed) ||
- detectByXML && svgTagInXMLRegex.Match(dataProcessed) {
- ct = SvgMimeType
- }
- }
-
- 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.
- // This works especially because audio files contain many unprintable/invalid characters like `0x00`
- ct2 := http.DetectContentType(data[3:])
- if strings.HasPrefix(ct2, "text/") {
- ct = ct2
- }
- }
-
- if ct == "application/ogg" {
- dataHead := data
- if len(dataHead) > 256 {
- dataHead = dataHead[:256] // only need to do a quick check for the file header
- }
- if bytes.Contains(dataHead, []byte("theora")) || bytes.Contains(dataHead, []byte("dirac")) {
- ct = "video/ogg" // ogg is only used for some video formats, and it's not popular
- } else {
- ct = "audio/ogg" // for most cases, it is used as an audio container
- }
- }
- 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
- }
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