430 lines
12 KiB
Go
430 lines
12 KiB
Go
package gziphandler
|
||
|
||
import (
|
||
"bufio"
|
||
"compress/gzip"
|
||
"fmt"
|
||
"io"
|
||
"net"
|
||
"net/http"
|
||
"strconv"
|
||
"strings"
|
||
"sync"
|
||
)
|
||
|
||
const (
|
||
vary = "Vary"
|
||
acceptEncoding = "Accept-Encoding"
|
||
contentEncoding = "Content-Encoding"
|
||
contentType = "Content-Type"
|
||
contentLength = "Content-Length"
|
||
)
|
||
|
||
type codings map[string]float64
|
||
|
||
const (
|
||
// DefaultQValue is the default qvalue to assign to an encoding if no explicit qvalue is set.
|
||
// This is actually kind of ambiguous in RFC 2616, so hopefully it's correct.
|
||
// The examples seem to indicate that it is.
|
||
DefaultQValue = 1.0
|
||
|
||
// 1500 bytes is the MTU size for the internet since that is the largest size allowed at the network layer.
|
||
// If you take a file that is 1300 bytes and compress it to 800 bytes, it’s still transmitted in that same 1500 byte packet regardless, so you’ve gained nothing.
|
||
// That being the case, you should restrict the gzip compression to files with a size greater than a single packet, 1400 bytes (1.4KB) is a safe value.
|
||
DefaultMinSize = 1400
|
||
)
|
||
|
||
// gzipWriterPools stores a sync.Pool for each compression level for reuse of
|
||
// gzip.Writers. Use poolIndex to covert a compression level to an index into
|
||
// gzipWriterPools.
|
||
var gzipWriterPools [gzip.BestCompression - gzip.BestSpeed + 2]*sync.Pool
|
||
|
||
func init() {
|
||
for i := gzip.BestSpeed; i <= gzip.BestCompression; i++ {
|
||
addLevelPool(i)
|
||
}
|
||
addLevelPool(gzip.DefaultCompression)
|
||
}
|
||
|
||
// poolIndex maps a compression level to its index into gzipWriterPools. It
|
||
// assumes that level is a valid gzip compression level.
|
||
func poolIndex(level int) int {
|
||
// gzip.DefaultCompression == -1, so we need to treat it special.
|
||
if level == gzip.DefaultCompression {
|
||
return gzip.BestCompression - gzip.BestSpeed + 1
|
||
}
|
||
return level - gzip.BestSpeed
|
||
}
|
||
|
||
func addLevelPool(level int) {
|
||
gzipWriterPools[poolIndex(level)] = &sync.Pool{
|
||
New: func() interface{} {
|
||
// NewWriterLevel only returns error on a bad level, we are guaranteeing
|
||
// that this will be a valid level so it is okay to ignore the returned
|
||
// error.
|
||
w, _ := gzip.NewWriterLevel(nil, level)
|
||
return w
|
||
},
|
||
}
|
||
}
|
||
|
||
// GzipResponseWriter provides an http.ResponseWriter interface, which gzips
|
||
// bytes before writing them to the underlying response. This doesn't close the
|
||
// writers, so don't forget to do that.
|
||
// It can be configured to skip response smaller than minSize.
|
||
type GzipResponseWriter struct {
|
||
http.ResponseWriter
|
||
index int // Index for gzipWriterPools.
|
||
gw *gzip.Writer
|
||
|
||
code int // Saves the WriteHeader value.
|
||
|
||
minSize int // Specifed the minimum response size to gzip. If the response length is bigger than this value, it is compressed.
|
||
buf []byte // Holds the first part of the write before reaching the minSize or the end of the write.
|
||
|
||
contentTypes []string // Only compress if the response is one of these content-types. All are accepted if empty.
|
||
}
|
||
|
||
type GzipResponseWriterWithCloseNotify struct {
|
||
*GzipResponseWriter
|
||
}
|
||
|
||
func (w GzipResponseWriterWithCloseNotify) CloseNotify() <-chan bool {
|
||
return w.ResponseWriter.(http.CloseNotifier).CloseNotify()
|
||
}
|
||
|
||
// Write appends data to the gzip writer.
|
||
func (w *GzipResponseWriter) Write(b []byte) (int, error) {
|
||
// If content type is not set.
|
||
if _, ok := w.Header()[contentType]; !ok {
|
||
// It infer it from the uncompressed body.
|
||
w.Header().Set(contentType, http.DetectContentType(b))
|
||
}
|
||
|
||
// GZIP responseWriter is initialized. Use the GZIP responseWriter.
|
||
if w.gw != nil {
|
||
n, err := w.gw.Write(b)
|
||
return n, err
|
||
}
|
||
|
||
// Save the write into a buffer for later use in GZIP responseWriter (if content is long enough) or at close with regular responseWriter.
|
||
// On the first write, w.buf changes from nil to a valid slice
|
||
w.buf = append(w.buf, b...)
|
||
|
||
// If the global writes are bigger than the minSize and we're about to write
|
||
// a response containing a content type we want to handle, enable
|
||
// compression.
|
||
if len(w.buf) >= w.minSize && handleContentType(w.contentTypes, w) && w.Header().Get(contentEncoding) == "" {
|
||
err := w.startGzip()
|
||
if err != nil {
|
||
return 0, err
|
||
}
|
||
}
|
||
|
||
return len(b), nil
|
||
}
|
||
|
||
// startGzip initialize any GZIP specific informations.
|
||
func (w *GzipResponseWriter) startGzip() error {
|
||
|
||
// Set the GZIP header.
|
||
w.Header().Set(contentEncoding, "gzip")
|
||
|
||
// if the Content-Length is already set, then calls to Write on gzip
|
||
// will fail to set the Content-Length header since its already set
|
||
// See: https://github.com/golang/go/issues/14975.
|
||
w.Header().Del(contentLength)
|
||
|
||
// Write the header to gzip response.
|
||
if w.code != 0 {
|
||
w.ResponseWriter.WriteHeader(w.code)
|
||
}
|
||
|
||
// Initialize the GZIP response.
|
||
w.init()
|
||
|
||
// Flush the buffer into the gzip response.
|
||
n, err := w.gw.Write(w.buf)
|
||
|
||
// This should never happen (per io.Writer docs), but if the write didn't
|
||
// accept the entire buffer but returned no specific error, we have no clue
|
||
// what's going on, so abort just to be safe.
|
||
if err == nil && n < len(w.buf) {
|
||
return io.ErrShortWrite
|
||
}
|
||
|
||
w.buf = nil
|
||
return err
|
||
}
|
||
|
||
// WriteHeader just saves the response code until close or GZIP effective writes.
|
||
func (w *GzipResponseWriter) WriteHeader(code int) {
|
||
if w.code == 0 {
|
||
w.code = code
|
||
}
|
||
}
|
||
|
||
// init graps a new gzip writer from the gzipWriterPool and writes the correct
|
||
// content encoding header.
|
||
func (w *GzipResponseWriter) init() {
|
||
// Bytes written during ServeHTTP are redirected to this gzip writer
|
||
// before being written to the underlying response.
|
||
gzw := gzipWriterPools[w.index].Get().(*gzip.Writer)
|
||
gzw.Reset(w.ResponseWriter)
|
||
w.gw = gzw
|
||
}
|
||
|
||
// Close will close the gzip.Writer and will put it back in the gzipWriterPool.
|
||
func (w *GzipResponseWriter) Close() error {
|
||
if w.gw == nil {
|
||
// Gzip not trigged yet, write out regular response.
|
||
if w.code != 0 {
|
||
w.ResponseWriter.WriteHeader(w.code)
|
||
}
|
||
if w.buf != nil {
|
||
_, writeErr := w.ResponseWriter.Write(w.buf)
|
||
// Returns the error if any at write.
|
||
if writeErr != nil {
|
||
return fmt.Errorf("gziphandler: write to regular responseWriter at close gets error: %q", writeErr.Error())
|
||
}
|
||
}
|
||
return nil
|
||
}
|
||
|
||
err := w.gw.Close()
|
||
gzipWriterPools[w.index].Put(w.gw)
|
||
w.gw = nil
|
||
return err
|
||
}
|
||
|
||
// Flush flushes the underlying *gzip.Writer and then the underlying
|
||
// http.ResponseWriter if it is an http.Flusher. This makes GzipResponseWriter
|
||
// an http.Flusher.
|
||
func (w *GzipResponseWriter) Flush() {
|
||
if w.gw == nil {
|
||
// Only flush once startGzip has been called.
|
||
//
|
||
// Flush is thus a no-op until the written body
|
||
// exceeds minSize.
|
||
return
|
||
}
|
||
|
||
w.gw.Flush()
|
||
|
||
if fw, ok := w.ResponseWriter.(http.Flusher); ok {
|
||
fw.Flush()
|
||
}
|
||
}
|
||
|
||
// Hijack implements http.Hijacker. If the underlying ResponseWriter is a
|
||
// Hijacker, its Hijack method is returned. Otherwise an error is returned.
|
||
func (w *GzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
|
||
if hj, ok := w.ResponseWriter.(http.Hijacker); ok {
|
||
return hj.Hijack()
|
||
}
|
||
return nil, nil, fmt.Errorf("http.Hijacker interface is not supported")
|
||
}
|
||
|
||
// verify Hijacker interface implementation
|
||
var _ http.Hijacker = &GzipResponseWriter{}
|
||
|
||
// MustNewGzipLevelHandler behaves just like NewGzipLevelHandler except that in
|
||
// an error case it panics rather than returning an error.
|
||
func MustNewGzipLevelHandler(level int) func(http.Handler) http.Handler {
|
||
wrap, err := NewGzipLevelHandler(level)
|
||
if err != nil {
|
||
panic(err)
|
||
}
|
||
return wrap
|
||
}
|
||
|
||
// NewGzipLevelHandler returns a wrapper function (often known as middleware)
|
||
// which can be used to wrap an HTTP handler to transparently gzip the response
|
||
// body if the client supports it (via the Accept-Encoding header). Responses will
|
||
// be encoded at the given gzip compression level. An error will be returned only
|
||
// if an invalid gzip compression level is given, so if one can ensure the level
|
||
// is valid, the returned error can be safely ignored.
|
||
func NewGzipLevelHandler(level int) (func(http.Handler) http.Handler, error) {
|
||
return NewGzipLevelAndMinSize(level, DefaultMinSize)
|
||
}
|
||
|
||
// NewGzipLevelAndMinSize behave as NewGzipLevelHandler except it let the caller
|
||
// specify the minimum size before compression.
|
||
func NewGzipLevelAndMinSize(level, minSize int) (func(http.Handler) http.Handler, error) {
|
||
return GzipHandlerWithOpts(CompressionLevel(level), MinSize(minSize))
|
||
}
|
||
|
||
func GzipHandlerWithOpts(opts ...option) (func(http.Handler) http.Handler, error) {
|
||
c := &config{
|
||
level: gzip.DefaultCompression,
|
||
minSize: DefaultMinSize,
|
||
}
|
||
|
||
for _, o := range opts {
|
||
o(c)
|
||
}
|
||
|
||
if err := c.validate(); err != nil {
|
||
return nil, err
|
||
}
|
||
|
||
return func(h http.Handler) http.Handler {
|
||
index := poolIndex(c.level)
|
||
|
||
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
|
||
w.Header().Add(vary, acceptEncoding)
|
||
if acceptsGzip(r) {
|
||
gw := &GzipResponseWriter{
|
||
ResponseWriter: w,
|
||
index: index,
|
||
minSize: c.minSize,
|
||
contentTypes: c.contentTypes,
|
||
}
|
||
defer gw.Close()
|
||
|
||
if _, ok := w.(http.CloseNotifier); ok {
|
||
gwcn := GzipResponseWriterWithCloseNotify{gw}
|
||
h.ServeHTTP(gwcn, r)
|
||
} else {
|
||
h.ServeHTTP(gw, r)
|
||
}
|
||
|
||
} else {
|
||
h.ServeHTTP(w, r)
|
||
}
|
||
})
|
||
}, nil
|
||
}
|
||
|
||
// Used for functional configuration.
|
||
type config struct {
|
||
minSize int
|
||
level int
|
||
contentTypes []string
|
||
}
|
||
|
||
func (c *config) validate() error {
|
||
if c.level != gzip.DefaultCompression && (c.level < gzip.BestSpeed || c.level > gzip.BestCompression) {
|
||
return fmt.Errorf("invalid compression level requested: %d", c.level)
|
||
}
|
||
|
||
if c.minSize < 0 {
|
||
return fmt.Errorf("minimum size must be more than zero")
|
||
}
|
||
|
||
return nil
|
||
}
|
||
|
||
type option func(c *config)
|
||
|
||
func MinSize(size int) option {
|
||
return func(c *config) {
|
||
c.minSize = size
|
||
}
|
||
}
|
||
|
||
func CompressionLevel(level int) option {
|
||
return func(c *config) {
|
||
c.level = level
|
||
}
|
||
}
|
||
|
||
func ContentTypes(types []string) option {
|
||
return func(c *config) {
|
||
c.contentTypes = []string{}
|
||
for _, v := range types {
|
||
c.contentTypes = append(c.contentTypes, strings.ToLower(v))
|
||
}
|
||
}
|
||
}
|
||
|
||
// GzipHandler wraps an HTTP handler, to transparently gzip the response body if
|
||
// the client supports it (via the Accept-Encoding header). This will compress at
|
||
// the default compression level.
|
||
func GzipHandler(h http.Handler) http.Handler {
|
||
wrapper, _ := NewGzipLevelHandler(gzip.DefaultCompression)
|
||
return wrapper(h)
|
||
}
|
||
|
||
// acceptsGzip returns true if the given HTTP request indicates that it will
|
||
// accept a gzipped response.
|
||
func acceptsGzip(r *http.Request) bool {
|
||
acceptedEncodings, _ := parseEncodings(r.Header.Get(acceptEncoding))
|
||
return acceptedEncodings["gzip"] > 0.0
|
||
}
|
||
|
||
// returns true if we've been configured to compress the specific content type.
|
||
func handleContentType(contentTypes []string, w http.ResponseWriter) bool {
|
||
// If contentTypes is empty we handle all content types.
|
||
if len(contentTypes) == 0 {
|
||
return true
|
||
}
|
||
|
||
ct := strings.ToLower(w.Header().Get(contentType))
|
||
for _, c := range contentTypes {
|
||
if c == ct {
|
||
return true
|
||
}
|
||
}
|
||
|
||
return false
|
||
}
|
||
|
||
// parseEncodings attempts to parse a list of codings, per RFC 2616, as might
|
||
// appear in an Accept-Encoding header. It returns a map of content-codings to
|
||
// quality values, and an error containing the errors encountered. It's probably
|
||
// safe to ignore those, because silently ignoring errors is how the internet
|
||
// works.
|
||
//
|
||
// See: http://tools.ietf.org/html/rfc2616#section-14.3.
|
||
func parseEncodings(s string) (codings, error) {
|
||
c := make(codings)
|
||
var e []string
|
||
|
||
for _, ss := range strings.Split(s, ",") {
|
||
coding, qvalue, err := parseCoding(ss)
|
||
|
||
if err != nil {
|
||
e = append(e, err.Error())
|
||
} else {
|
||
c[coding] = qvalue
|
||
}
|
||
}
|
||
|
||
// TODO (adammck): Use a proper multi-error struct, so the individual errors
|
||
// can be extracted if anyone cares.
|
||
if len(e) > 0 {
|
||
return c, fmt.Errorf("errors while parsing encodings: %s", strings.Join(e, ", "))
|
||
}
|
||
|
||
return c, nil
|
||
}
|
||
|
||
// parseCoding parses a single conding (content-coding with an optional qvalue),
|
||
// as might appear in an Accept-Encoding header. It attempts to forgive minor
|
||
// formatting errors.
|
||
func parseCoding(s string) (coding string, qvalue float64, err error) {
|
||
for n, part := range strings.Split(s, ";") {
|
||
part = strings.TrimSpace(part)
|
||
qvalue = DefaultQValue
|
||
|
||
if n == 0 {
|
||
coding = strings.ToLower(part)
|
||
} else if strings.HasPrefix(part, "q=") {
|
||
qvalue, err = strconv.ParseFloat(strings.TrimPrefix(part, "q="), 64)
|
||
|
||
if qvalue < 0.0 {
|
||
qvalue = 0.0
|
||
} else if qvalue > 1.0 {
|
||
qvalue = 1.0
|
||
}
|
||
}
|
||
}
|
||
|
||
if coding == "" {
|
||
err = fmt.Errorf("empty content-coding")
|
||
}
|
||
|
||
return
|
||
}
|