type_unix.go

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build unix || (js && wasm) || wasip1
     6  
     7  package mime
     8  
     9  import (
    10  	"bufio"
    11  	"os"
    12  	"strings"
    13  )
    14  
    15  func init() {
    16  	osInitMime = initMimeUnix
    17  }
    18  
    19  // See https://specifications.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-0.21.html
    20  // for the FreeDesktop Shared MIME-info Database specification.
    21  var mimeGlobs = []string{
    22  	"/usr/local/share/mime/globs2",
    23  	"/usr/share/mime/globs2",
    24  }
    25  
    26  // Common locations for mime.types files on unix.
    27  var typeFiles = []string{
    28  	"/etc/mime.types",
    29  	"/etc/apache2/mime.types",
    30  	"/etc/apache/mime.types",
    31  	"/etc/httpd/conf/mime.types",
    32  }
    33  
    34  func loadMimeGlobsFile(filename string) error {
    35  	f, err := os.Open(filename)
    36  	if err != nil {
    37  		return err
    38  	}
    39  	defer f.Close()
    40  
    41  	scanner := bufio.NewScanner(f)
    42  	for scanner.Scan() {
    43  		// Each line should be of format: weight:mimetype:glob[:morefields...]
    44  		fields := strings.Split(scanner.Text(), ":")
    45  		if len(fields) < 3 || len(fields[0]) < 1 || len(fields[2]) < 3 {
    46  			continue
    47  		} else if fields[0][0] == '#' || fields[2][0] != '*' || fields[2][1] != '.' {
    48  			continue
    49  		}
    50  
    51  		extension := fields[2][1:]
    52  		if strings.ContainsAny(extension, "?*[") {
    53  			// Not a bare extension, but a glob. Ignore for now:
    54  			// - we do not have an implementation for this glob
    55  			//   syntax (translation to path/filepath.Match could
    56  			//   be possible)
    57  			// - support for globs with weight ordering would have
    58  			//   performance impact to all lookups to support the
    59  			//   rarely seen glob entries
    60  			// - trying to match glob metacharacters literally is
    61  			//   not useful
    62  			continue
    63  		}
    64  		if _, ok := mimeTypes.Load(extension); ok {
    65  			// We've already seen this extension.
    66  			// The file is in weight order, so we keep
    67  			// the first entry that we see.
    68  			continue
    69  		}
    70  
    71  		setExtensionType(extension, fields[1])
    72  	}
    73  	if err := scanner.Err(); err != nil {
    74  		panic(err)
    75  	}
    76  	return nil
    77  }
    78  
    79  func loadMimeFile(filename string) {
    80  	f, err := os.Open(filename)
    81  	if err != nil {
    82  		return
    83  	}
    84  	defer f.Close()
    85  
    86  	scanner := bufio.NewScanner(f)
    87  	for scanner.Scan() {
    88  		fields := strings.Fields(scanner.Text())
    89  		if len(fields) <= 1 || fields[0][0] == '#' {
    90  			continue
    91  		}
    92  		mimeType := fields[0]
    93  		for _, ext := range fields[1:] {
    94  			if ext[0] == '#' {
    95  				break
    96  			}
    97  			setExtensionType("."+ext, mimeType)
    98  		}
    99  	}
   100  	if err := scanner.Err(); err != nil {
   101  		panic(err)
   102  	}
   103  }
   104  
   105  func initMimeUnix() {
   106  	for _, filename := range mimeGlobs {
   107  		if err := loadMimeGlobsFile(filename); err == nil {
   108  			return // Stop checking more files if mimetype database is found.
   109  		}
   110  	}
   111  
   112  	// Fallback if no system-generated mimetype database exists.
   113  	for _, filename := range typeFiles {
   114  		loadMimeFile(filename)
   115  	}
   116  }
   117  
   118  func initMimeForTests() map[string]string {
   119  	mimeGlobs = []string{""}
   120  	typeFiles = []string{"testdata/test.types"}
   121  	return map[string]string{
   122  		".T1":  "application/test",
   123  		".t2":  "text/test; charset=utf-8",
   124  		".png": "image/png",
   125  	}
   126  }
   127
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