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cache.go
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cache.go
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package httpfs
import (
"bytes"
"context"
"fmt"
"io"
"net/http"
"os"
"path"
"regexp"
"sort"
"strings"
"sync"
"time"
"github.com/kataras/compress"
)
var (
// Images a regexp that can be used on `DefaultCacheOptions.CompressIgnore`
// to ignore already-compressed images (and pdf).
Images = regexp.MustCompile("((.*).pdf|(.*).jpg|(.*).jpeg|(.*).gif|(.*).tif|(.*).tiff)$")
// AllEncodings holds the builtin available compression algorithms (encodings),
// can be used on `DefaultCacheOptions.Encodings` field.
// List of available content encodings:
// - gzip,
// - deflate,
// - br(brotli) and
// - snappy.
AllEncodings = compress.DefaultOffers
// DefaultCacheOptions holds the recommended settings
// for `CacheOptions` to pass on `Cache` function.
DefaultCacheOptions = CacheOptions{
CompressMinSize: 300 * B, // Another good value is 1400.
// .pdf, .jpg, .jpeg, .gif, .png, .tif, .tiff
CompressIgnore: Images,
// gzip, deflate, br(brotli), snappy
Encodings: AllEncodings,
}
)
// CacheOptions holds the options for the cached file system.
// See `Cache` package-level function.
type CacheOptions struct {
// Minimum contents size for compression in bytes.
CompressMinSize int64
// Ignore compress files that match this pattern.
CompressIgnore *regexp.Regexp
// The available sever's encodings to be negotiated with the client's needs,
// common values: gzip, br.
Encodings []string
}
// MustCache same as `Cache` but it panics on init errors.
func MustCache(fs http.FileSystem, options CacheOptions) http.FileSystem {
c, err := Cache(fs, options)
if err != nil {
panic(err)
}
return c
}
// Cache returns a http.FileSystem which serves in-memory cached (compressed) files.
// Look `Verbose` function to print out information while in development status.
func Cache(fs http.FileSystem, options CacheOptions) (http.FileSystem, error) {
start := time.Now()
names, err := findNames(fs, "/")
if err != nil {
return fs, err
}
sort.Slice(names, func(i, j int) bool {
return strings.Count(names[j], "/") > strings.Count(names[i], "/")
})
dirs, err := findDirs(fs, names)
if err != nil {
return fs, err
}
files, err := cacheFiles(context.Background(), fs, names,
options.Encodings, options.CompressMinSize, options.CompressIgnore)
if err != nil {
return fs, err
}
ttc := time.Since(start)
c := &cacheFS{ttc: ttc, n: len(names), dirs: dirs, files: files, algs: options.Encodings}
return c, nil
}
// VerboseFull if enabled then Verbose will print each file's sizes.
var VerboseFull = false
// Verbose accepts a FileSystem (a cached one)
// and prints out the total reduced size per compression.
// See `Cache` function too.
func Verbose(fs http.FileSystem) {
switch v := fs.(type) {
case *cacheFS:
verboseCacheFS(v)
default:
}
}
func verboseCacheFS(fs *cacheFS) {
var (
totalLength int64
totalCompressedLength = make(map[string]int64)
totalCompressedContents int64
)
for name, f := range fs.files {
uncompressed := f.algs[""]
totalLength += int64(len(uncompressed))
if VerboseFull {
fmt.Printf("%s (%s)\n", name, FormatBytes(int64(len(uncompressed))))
}
for alg, contents := range f.algs {
if alg == "" {
continue
}
totalCompressedContents++
if len(alg) < 7 {
alg += strings.Repeat(" ", 7-len(alg))
}
totalCompressedLength[alg] += int64(len(contents))
if VerboseFull {
fmt.Printf("%s (%s)\n", alg, FormatBytes(int64(len(contents))))
}
}
}
fmt.Printf("Time to complete the compression and caching of [%d/%d] files: %s\n", totalCompressedContents/int64(len(fs.algs)), fs.n, fs.ttc)
fmt.Printf("Total size reduced from %s to:\n", FormatBytes(totalLength))
for alg, length := range totalCompressedLength {
// https://en.wikipedia.org/wiki/Data_compression_ratio
reducedRatio := 1 - float64(length)/float64(totalLength)
fmt.Printf("%s (%s) [%.2f%%]\n", alg, FormatBytes(length), reducedRatio*100)
}
}
type cacheFS struct {
ttc time.Duration // time to complete
n int // total files
dirs map[string]*dir
files fileMap
algs []string
}
var _ http.FileSystem = (*cacheFS)(nil)
// Open returns the http.File based on "name".
// If file, it always returns a cached file of uncompressed data.
// See `Ropen` too.
func (c *cacheFS) Open(name string) (http.File, error) {
// we always fetch with the sep,
// as http requests will do,
// and the filename's info.Name() is always base
// and without separator prefix
// (keep note, we need that fileInfo
// wrapper because go-bindata's Name originally
// returns the fullname while the http.Dir returns the basename).
if name == "" || name[0] != '/' {
name = "/" + name
}
if d, ok := c.dirs[name]; ok {
return d, nil
}
if f, ok := c.files[name]; ok {
return f.Get("")
}
return nil, os.ErrNotExist
}
type ropener interface {
Ropen(name string, r *http.Request) (http.File, error)
}
var _ ropener = (*cacheFS)(nil)
// Ropen returns the http.File based on "name".
// If file, it negotiates the content encoding,
// based on the given algorithms, and
// returns the cached file with compressed data,
// if the encoding was empty then it
// returns the cached file with its original, uncompressed data.
//
// A check of `GetEncoding(file)` is required to set
// response headers.
//
// Note: We don't require a response writer to set the headers
// because the caller of this method may stop the operation
// before file's contents are written to the client.
func (c *cacheFS) Ropen(name string, r *http.Request) (http.File, error) {
if name == "" || name[0] != '/' {
name = "/" + name
}
if d, ok := c.dirs[name]; ok {
return d, nil
}
if f, ok := c.files[name]; ok {
encoding, _ := compress.GetEncoding(r, c.algs)
return f.Get(encoding)
}
return nil, os.ErrNotExist
}
// GetEncoding returns the encoding of an http.File.
// If the "f" file was created by a `Cache` call then
// it returns the content encoding that this file was cached with.
// It returns empty string for files that
// were too small or ignored to be compressed.
//
// It also reports whether the "f" is a cached file or not.
func GetEncoding(f http.File) (string, bool) {
if f == nil {
return "", false
}
ff, ok := f.(*file)
if !ok {
return "", false
}
return ff.alg, true
}
// type fileMap map[string] /* path */ map[string] /*compression alg or empty for original */ []byte /*contents */
type fileMap map[string]*file
func cacheFiles(ctx context.Context, fs http.FileSystem, names []string, compressAlgs []string, compressMinSize int64, compressIgnore *regexp.Regexp) (fileMap, error) {
ctx, cancel := context.WithCancel(ctx)
defer cancel()
list := make(fileMap, len(names))
mutex := new(sync.Mutex)
cache := func(name string) error {
f, err := fs.Open(name)
if err != nil {
return err
}
inf, err := f.Stat()
if err != nil {
f.Close()
return err
}
fi := newFileInfo(path.Base(name), inf.Mode(), inf.ModTime())
contents, err := io.ReadAll(f)
f.Close()
if err != nil {
return err
}
algs := make(map[string][]byte, len(compressAlgs)+1)
algs[""] = contents // original contents.
mutex.Lock()
list[name] = newFile(name, fi, algs)
mutex.Unlock()
if compressMinSize > 0 && compressMinSize > int64(len(contents)) {
return nil
}
if compressIgnore != nil && compressIgnore.MatchString(name) {
return nil
}
// Note:
// We can fire a new goroutine for each compression of the same file
// but this will have an impact on CPU cost if
// thousands of files running 4 compressions at the same time,
// so, unless requested keep it as it's.
buf := new(bytes.Buffer)
for _, alg := range compressAlgs {
select {
case <-ctx.Done():
return ctx.Err() // stop all compressions if at least one file failed to.
default:
}
if alg == "brotli" {
alg = "br"
}
w, err := compress.NewWriter(buf, strings.ToLower(alg), -1)
if err != nil {
return err
}
_, err = w.Write(contents)
w.Close()
if err != nil {
return err
}
bs := buf.Bytes()
dest := make([]byte, len(bs))
copy(dest, bs)
algs[alg] = dest
buf.Reset()
}
return nil
}
var (
err error
wg sync.WaitGroup
errOnce sync.Once
)
for _, name := range names {
wg.Add(1)
go func(name string) {
defer wg.Done()
if fnErr := cache(name); fnErr != nil {
errOnce.Do(func() {
err = fnErr
cancel()
})
}
}(name)
}
wg.Wait()
return list, err
}
type cacheStoreFile interface {
Get(compressionAlgorithm string) (http.File, error)
}
type file struct {
io.ReadSeeker // nil on cache store and filled on file Get.
algs map[string][]byte // non empty for store and nil for files.
alg string // empty for cache store, filled with the compression algorithm of this file (useful to decompress).
name string
baseName string
info os.FileInfo
}
var _ http.File = (*file)(nil)
var _ cacheStoreFile = (*file)(nil)
func newFile(name string, fi os.FileInfo, algs map[string][]byte) *file {
return &file{
name: name,
baseName: path.Base(name),
info: fi,
algs: algs,
}
}
func (f *file) Close() error { return nil }
func (f *file) Readdir(count int) ([]os.FileInfo, error) { return nil, os.ErrNotExist }
func (f *file) Stat() (os.FileInfo, error) { return f.info, nil }
// Get returns a new http.File to be served.
// Caller should check if a specific http.File has this method as well.
func (f *file) Get(alg string) (http.File, error) {
// The "alg" can be empty for non-compressed file contents.
// We don't need a new structure.
if contents, ok := f.algs[alg]; ok {
return &file{
name: f.name,
baseName: f.baseName,
info: f.info,
alg: alg,
ReadSeeker: bytes.NewReader(contents),
}, nil
}
// When client accept compression but cached contents are not compressed,
// e.g. file too small or ignored one.
return f.Get("")
}
/*
Remember, the decompressed data already exist in the empty Get("").
We do NOT need this (unless requested):
func (f *file) Decompress(w io.Writer) (int64, error) {
if f.alg == "" {
return 0, os.ErrNotExist
}
cr, err := compress.NewReader(f, f.alg)
if err != nil {
return 0, err
}
n, err := io.Copy(w, cr)
cr.Close()
return n, err
}
*/
func findNames(fs http.FileSystem, name string) ([]string, error) {
f, err := fs.Open(name)
if err != nil {
return nil, err
}
defer f.Close()
fi, err := f.Stat()
if err != nil {
return nil, err
}
if !fi.IsDir() {
return []string{name}, nil
}
fileinfos, err := f.Readdir(-1)
if err != nil {
return nil, err
}
files := make([]string, 0)
for _, info := range fileinfos {
// Note:
// go-bindata has absolute names with os.Separator,
// http.Dir the basename.
filename := toBaseName(info.Name())
fullname := path.Join(name, filename)
if fullname == name { // prevent looping through itself when fs is cacheFS.
continue
}
rfiles, err := findNames(fs, fullname)
if err != nil {
return nil, err
}
files = append(files, rfiles...)
}
return files, nil
}
type fileInfo struct {
baseName string
modTime time.Time
isDir bool
mode os.FileMode
}
var _ os.FileInfo = (*fileInfo)(nil)
func newFileInfo(baseName string, mode os.FileMode, modTime time.Time) *fileInfo {
return &fileInfo{
baseName: baseName,
modTime: modTime,
mode: mode,
isDir: mode == os.ModeDir,
}
}
func (fi *fileInfo) Close() error { return nil }
func (fi *fileInfo) Name() string { return fi.baseName }
func (fi *fileInfo) Mode() os.FileMode { return fi.mode }
func (fi *fileInfo) ModTime() time.Time { return fi.modTime }
func (fi *fileInfo) IsDir() bool { return fi.isDir }
func (fi *fileInfo) Size() int64 { return 0 }
func (fi *fileInfo) Sys() interface{} { return fi }
type dir struct {
os.FileInfo // *fileInfo
io.ReadSeeker // nil
name string // fullname, for any case.
baseName string
children []os.FileInfo // a slice of *fileInfo
}
var _ os.FileInfo = (*dir)(nil)
var _ http.File = (*dir)(nil)
func (d *dir) Close() error { return nil }
func (d *dir) Name() string { return d.baseName }
func (d *dir) Stat() (os.FileInfo, error) { return d.FileInfo, nil }
func (d *dir) Readdir(count int) ([]os.FileInfo, error) {
return d.children, nil
}
func newDir(fi os.FileInfo, fullname string) *dir {
baseName := path.Base(fullname)
return &dir{
FileInfo: newFileInfo(baseName, os.ModeDir, fi.ModTime()),
name: fullname,
baseName: baseName,
}
}
var _ http.File = (*dir)(nil)
// returns unorderded map of directories both reclusive and flat.
func findDirs(fs http.FileSystem, names []string) (map[string]*dir, error) {
dirs := make(map[string]*dir, 0)
for _, name := range names {
f, err := fs.Open(name)
if err != nil {
return nil, err
}
inf, err := f.Stat()
if err != nil {
return nil, err
}
dirName := path.Dir(name)
d, ok := dirs[dirName]
if !ok {
fi := newFileInfo(path.Base(dirName), os.ModeDir, inf.ModTime())
d = newDir(fi, dirName)
dirs[dirName] = d
}
fi := newFileInfo(path.Base(name), inf.Mode(), inf.ModTime())
// Add the directory file info (=this dir) to the parent one,
// so `ShowList` can render sub-directories of this dir.
parentName := path.Dir(dirName)
if parent, hasParent := dirs[parentName]; hasParent {
parent.children = append(parent.children, d)
}
d.children = append(d.children, fi)
}
return dirs, nil
}