libgo: update to go1.9

[official-gcc.git] / libgo / go / mime / type.go

// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package mime implements parts of the MIME spec.
package mime

import (
        "fmt"
        "strings"
        "sync"
)

var (
        mimeTypes      sync.Map // map[string]string; ".Z" => "application/x-compress"
        mimeTypesLower sync.Map // map[string]string; ".z" => "application/x-compress"

        // extensions maps from MIME type to list of lowercase file
        // extensions: "image/jpeg" => [".jpg", ".jpeg"]
        extensionsMu sync.Mutex // Guards stores (but not loads) on extensions.
        extensions   sync.Map   // map[string][]string; slice values are append-only.
)

func clearSyncMap(m *sync.Map) {
        m.Range(func(k, _ interface{}) bool {
                m.Delete(k)
                return true
        })
}

// setMimeTypes is used by initMime's non-test path, and by tests.
func setMimeTypes(lowerExt, mixExt map[string]string) {
        clearSyncMap(&mimeTypes)
        clearSyncMap(&mimeTypesLower)
        clearSyncMap(&extensions)

        for k, v := range lowerExt {
                mimeTypesLower.Store(k, v)
        }
        for k, v := range mixExt {
                mimeTypes.Store(k, v)
        }

        extensionsMu.Lock()
        defer extensionsMu.Unlock()
        for k, v := range lowerExt {
                justType, _, err := ParseMediaType(v)
                if err != nil {
                        panic(err)
                }
                var exts []string
                if ei, ok := extensions.Load(k); ok {
                        exts = ei.([]string)
                }
                extensions.Store(justType, append(exts, k))
        }
}

var builtinTypesLower = map[string]string{
        ".css":  "text/css; charset=utf-8",
        ".gif":  "image/gif",
        ".htm":  "text/html; charset=utf-8",
        ".html": "text/html; charset=utf-8",
        ".jpg":  "image/jpeg",
        ".js":   "application/x-javascript",
        ".pdf":  "application/pdf",
        ".png":  "image/png",
        ".svg":  "image/svg+xml",
        ".xml":  "text/xml; charset=utf-8",
}

var once sync.Once // guards initMime

var testInitMime, osInitMime func()

func initMime() {
        if fn := testInitMime; fn != nil {
                fn()
        } else {
                setMimeTypes(builtinTypesLower, builtinTypesLower)
                osInitMime()
        }
}

// TypeByExtension returns the MIME type associated with the file extension ext.
// The extension ext should begin with a leading dot, as in ".html".
// When ext has no associated type, TypeByExtension returns "".
//
// Extensions are looked up first case-sensitively, then case-insensitively.
//
// The built-in table is small but on unix it is augmented by the local
// system's mime.types file(s) if available under one or more of these
// names:
//
//   /etc/mime.types
//   /etc/apache2/mime.types
//   /etc/apache/mime.types
//
// On Windows, MIME types are extracted from the registry.
//
// Text types have the charset parameter set to "utf-8" by default.
func TypeByExtension(ext string) string {
        once.Do(initMime)

        // Case-sensitive lookup.
        if v, ok := mimeTypes.Load(ext); ok {
                return v.(string)
        }

        // Case-insensitive lookup.
        // Optimistically assume a short ASCII extension and be
        // allocation-free in that case.
        var buf [10]byte
        lower := buf[:0]
        const utf8RuneSelf = 0x80 // from utf8 package, but not importing it.
        for i := 0; i < len(ext); i++ {
                c := ext[i]
                if c >= utf8RuneSelf {
                        // Slow path.
                        si, _ := mimeTypesLower.Load(strings.ToLower(ext))
                        s, _ := si.(string)
                        return s
                }
                if 'A' <= c && c <= 'Z' {
                        lower = append(lower, c+('a'-'A'))
                } else {
                        lower = append(lower, c)
                }
        }
        si, _ := mimeTypesLower.Load(string(lower))
        s, _ := si.(string)
        return s
}

// ExtensionsByType returns the extensions known to be associated with the MIME
// type typ. The returned extensions will each begin with a leading dot, as in
// ".html". When typ has no associated extensions, ExtensionsByType returns an
// nil slice.
func ExtensionsByType(typ string) ([]string, error) {
        justType, _, err := ParseMediaType(typ)
        if err != nil {
                return nil, err
        }

        once.Do(initMime)
        s, ok := extensions.Load(justType)
        if !ok {
                return nil, nil
        }
        return append([]string{}, s.([]string)...), nil
}

// AddExtensionType sets the MIME type associated with
// the extension ext to typ. The extension should begin with
// a leading dot, as in ".html".
func AddExtensionType(ext, typ string) error {
        if !strings.HasPrefix(ext, ".") {
                return fmt.Errorf("mime: extension %q missing leading dot", ext)
        }
        once.Do(initMime)
        return setExtensionType(ext, typ)
}

func setExtensionType(extension, mimeType string) error {
        justType, param, err := ParseMediaType(mimeType)
        if err != nil {
                return err
        }
        if strings.HasPrefix(mimeType, "text/") && param["charset"] == "" {
                param["charset"] = "utf-8"
                mimeType = FormatMediaType(mimeType, param)
        }
        extLower := strings.ToLower(extension)

        mimeTypes.Store(extension, mimeType)
        mimeTypesLower.Store(extLower, mimeType)

        extensionsMu.Lock()
        defer extensionsMu.Unlock()
        var exts []string
        if ei, ok := extensions.Load(justType); ok {
                exts = ei.([]string)
        }
        for _, v := range exts {
                if v == extLower {
                        return nil
                }
        }
        extensions.Store(justType, append(exts, extLower))
        return nil
}