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echo/middleware/compress.go

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package middleware
import (
"bufio"
"bytes"
"compress/gzip"
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"errors"
"io"
"net"
"net/http"
"strings"
"sync"
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"github.com/labstack/echo/v5"
)
const (
gzipScheme = "gzip"
)
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// GzipConfig defines the config for Gzip middleware.
type GzipConfig struct {
// Skipper defines a function to skip middleware.
Skipper Skipper
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// Gzip compression level.
// Optional. Default value -1.
Level int
// Length threshold before gzip compression is applied.
// Optional. Default value 0.
//
// Most of the time you will not need to change the default. Compressing
// a short response might increase the transmitted data because of the
// gzip format overhead. Compressing the response will also consume CPU
// and time on the server and the client (for decompressing). Depending on
// your use case such a threshold might be useful.
//
// See also:
// https://webmasters.stackexchange.com/questions/31750/what-is-recommended-minimum-object-size-for-gzip-performance-benefits
MinLength int
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}
type gzipResponseWriter struct {
io.Writer
http.ResponseWriter
wroteHeader bool
wroteBody bool
minLength int
minLengthExceeded bool
buffer *bytes.Buffer
code int
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}
// Gzip returns a middleware which compresses HTTP response using gzip compression scheme.
func Gzip() echo.MiddlewareFunc {
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return GzipWithConfig(GzipConfig{})
}
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// GzipWithConfig returns a middleware which compresses HTTP response using gzip compression scheme.
func GzipWithConfig(config GzipConfig) echo.MiddlewareFunc {
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return toMiddlewareOrPanic(config)
}
// ToMiddleware converts GzipConfig to middleware or returns an error for invalid configuration
func (config GzipConfig) ToMiddleware() (echo.MiddlewareFunc, error) {
if config.Skipper == nil {
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config.Skipper = DefaultSkipper
}
if config.Level < -2 || config.Level > 9 { // these are consts: gzip.HuffmanOnly and gzip.BestCompression
return nil, errors.New("invalid gzip level")
}
if config.Level == 0 {
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config.Level = -1
}
if config.MinLength < 0 {
config.MinLength = 0
}
pool := gzipCompressPool(config)
bpool := bufferPool()
return func(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) error {
if config.Skipper(c) {
return next(c)
}
res := c.Response()
res.Header().Add(echo.HeaderVary, echo.HeaderAcceptEncoding)
if strings.Contains(c.Request().Header.Get(echo.HeaderAcceptEncoding), gzipScheme) {
i := pool.Get()
w, ok := i.(*gzip.Writer)
if !ok {
return echo.NewHTTPErrorWithInternal(http.StatusInternalServerError, i.(error))
}
rw := res.Writer
w.Reset(rw)
buf := bpool.Get().(*bytes.Buffer)
buf.Reset()
grw := &gzipResponseWriter{Writer: w, ResponseWriter: rw, minLength: config.MinLength, buffer: buf}
defer func() {
// There are different reasons for cases when we have not yet written response to the client and now need to do so.
// a) handler response had only response code and no response body (ala 404 or redirects etc). Response code need to be written now.
// b) body is shorter than our minimum length threshold and being buffered currently and needs to be written
if !grw.wroteBody {
if res.Header().Get(echo.HeaderContentEncoding) == gzipScheme {
res.Header().Del(echo.HeaderContentEncoding)
}
if grw.wroteHeader {
rw.WriteHeader(grw.code)
}
// We have to reset response to it's pristine state when
// nothing is written to body or error is returned.
// See issue #424, #407.
res.Writer = rw
w.Reset(io.Discard)
} else if !grw.minLengthExceeded {
// Write uncompressed response
res.Writer = rw
if grw.wroteHeader {
grw.ResponseWriter.WriteHeader(grw.code)
}
grw.buffer.WriteTo(rw)
w.Reset(io.Discard)
}
w.Close()
bpool.Put(buf)
pool.Put(w)
}()
res.Writer = grw
}
return next(c)
}
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}, nil
}
func (w *gzipResponseWriter) WriteHeader(code int) {
w.Header().Del(echo.HeaderContentLength) // Issue #444
w.wroteHeader = true
// Delay writing of the header until we know if we'll actually compress the response
w.code = code
}
func (w *gzipResponseWriter) Write(b []byte) (int, error) {
if w.Header().Get(echo.HeaderContentType) == "" {
w.Header().Set(echo.HeaderContentType, http.DetectContentType(b))
}
w.wroteBody = true
if !w.minLengthExceeded {
n, err := w.buffer.Write(b)
if w.buffer.Len() >= w.minLength {
w.minLengthExceeded = true
// The minimum length is exceeded, add Content-Encoding header and write the header
w.Header().Set(echo.HeaderContentEncoding, gzipScheme) // Issue #806
if w.wroteHeader {
w.ResponseWriter.WriteHeader(w.code)
}
return w.Writer.Write(w.buffer.Bytes())
}
return n, err
}
return w.Writer.Write(b)
}
func (w *gzipResponseWriter) Flush() {
if !w.minLengthExceeded {
// Enforce compression because we will not know how much more data will come
w.minLengthExceeded = true
w.Header().Set(echo.HeaderContentEncoding, gzipScheme) // Issue #806
if w.wroteHeader {
w.ResponseWriter.WriteHeader(w.code)
}
w.Writer.Write(w.buffer.Bytes())
}
w.Writer.(*gzip.Writer).Flush()
if flusher, ok := w.ResponseWriter.(http.Flusher); ok {
flusher.Flush()
}
}
func (w *gzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
return w.ResponseWriter.(http.Hijacker).Hijack()
}
func (w *gzipResponseWriter) Push(target string, opts *http.PushOptions) error {
if p, ok := w.ResponseWriter.(http.Pusher); ok {
return p.Push(target, opts)
}
return http.ErrNotSupported
}
func gzipCompressPool(config GzipConfig) sync.Pool {
return sync.Pool{
New: func() interface{} {
w, err := gzip.NewWriterLevel(io.Discard, config.Level)
if err != nil {
return err
}
return w
},
}
}
func bufferPool() sync.Pool {
return sync.Pool{
New: func() interface{} {
b := &bytes.Buffer{}
return b
},
}
}