pki/vendor/github.com/labstack/echo/v4/middleware/compress.go

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// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: © 2015 LabStack LLC and Echo contributors
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package middleware
import (
"bufio"
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"bytes"
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"compress/gzip"
"io"
"net"
"net/http"
"strings"
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"sync"
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"github.com/labstack/echo/v4"
)
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// GzipConfig defines the config for Gzip middleware.
type GzipConfig struct {
// Skipper defines a function to skip middleware.
Skipper Skipper
// Gzip compression level.
// Optional. Default value -1.
Level int `yaml:"level"`
// 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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const (
gzipScheme = "gzip"
)
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// DefaultGzipConfig is the default Gzip middleware config.
var DefaultGzipConfig = GzipConfig{
Skipper: DefaultSkipper,
Level: -1,
MinLength: 0,
}
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// Gzip returns a middleware which compresses HTTP response using gzip compression
// scheme.
func Gzip() echo.MiddlewareFunc {
return GzipWithConfig(DefaultGzipConfig)
}
// GzipWithConfig return Gzip middleware with config.
// See: `Gzip()`.
func GzipWithConfig(config GzipConfig) echo.MiddlewareFunc {
// Defaults
if config.Skipper == nil {
config.Skipper = DefaultGzipConfig.Skipper
}
if config.Level == 0 {
config.Level = DefaultGzipConfig.Level
}
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if config.MinLength < 0 {
config.MinLength = DefaultGzipConfig.MinLength
}
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pool := gzipCompressPool(config)
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bpool := bufferPool()
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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) {
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i := pool.Get()
w, ok := i.(*gzip.Writer)
if !ok {
return echo.NewHTTPError(http.StatusInternalServerError, i.(error).Error())
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}
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rw := res.Writer
w.Reset(rw)
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buf := bpool.Get().(*bytes.Buffer)
buf.Reset()
grw := &gzipResponseWriter{Writer: w, ResponseWriter: rw, minLength: config.MinLength, buffer: buf}
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defer func() {
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// 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
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if !grw.wroteBody {
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if res.Header().Get(echo.HeaderContentEncoding) == gzipScheme {
res.Header().Del(echo.HeaderContentEncoding)
}
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if grw.wroteHeader {
rw.WriteHeader(grw.code)
}
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// 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
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w.Reset(io.Discard)
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} 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)
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}
w.Close()
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bpool.Put(buf)
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pool.Put(w)
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}()
res.Writer = grw
}
return next(c)
}
}
}
func (w *gzipResponseWriter) WriteHeader(code int) {
w.Header().Del(echo.HeaderContentLength) // Issue #444
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w.wroteHeader = true
// Delay writing of the header until we know if we'll actually compress the response
w.code = code
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}
func (w *gzipResponseWriter) Write(b []byte) (int, error) {
if w.Header().Get(echo.HeaderContentType) == "" {
w.Header().Set(echo.HeaderContentType, http.DetectContentType(b))
}
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w.wroteBody = true
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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
}
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return w.Writer.Write(b)
}
func (w *gzipResponseWriter) Flush() {
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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())
}
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w.Writer.(*gzip.Writer).Flush()
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_ = responseControllerFlush(w.ResponseWriter)
}
func (w *gzipResponseWriter) Unwrap() http.ResponseWriter {
return w.ResponseWriter
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}
func (w *gzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
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return responseControllerHijack(w.ResponseWriter)
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}
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
}
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func gzipCompressPool(config GzipConfig) sync.Pool {
return sync.Pool{
New: func() interface{} {
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w, err := gzip.NewWriterLevel(io.Discard, config.Level)
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if err != nil {
return err
}
return w
},
}
}
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func bufferPool() sync.Pool {
return sync.Pool{
New: func() interface{} {
b := &bytes.Buffer{}
return b
},
}
}