96 lines
2.1 KiB
Go
96 lines
2.1 KiB
Go
package assets
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import (
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"bytes"
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"compress/gzip"
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"crypto/md5"
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"embed"
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"fmt"
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"net/http"
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"strings"
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)
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//go:embed *.ico *.html *.css
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var assets embed.FS
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func ReadFile(name string) ([]byte, error) {
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return assets.ReadFile(name)
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}
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type StaticContent struct {
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Type string
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Content []byte
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ETag string
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GZIPContent []byte
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GZIPETag string
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}
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func NewStaticContent(name string, mime string) (*StaticContent, error) {
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// Load data
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data, err := assets.ReadFile(name)
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if err != nil {
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return nil, err
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}
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sc := &StaticContent{Type: mime, Content: data}
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// Set a default Content-Type, if needed
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if sc.Type == "" {
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sc.Type = "application/octet-stream"
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}
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// Populate ETag
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sc.ETag = fmt.Sprintf("%x", md5.Sum(sc.Content))
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var buf bytes.Buffer
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gz, _ := gzip.NewWriterLevel(&buf, gzip.BestCompression)
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defer gz.Close()
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if _, err := gz.Write(sc.Content); err != nil {
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return nil, err
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}
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if err := gz.Flush(); err != nil {
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return nil, err
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}
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// Using gzip encoding adds a minimum of 24 characters to the HTTP
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// header, so only accept gzip encoding if we save that much or more
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if (buf.Len() + 24) < len(sc.Content) {
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sc.GZIPContent = buf.Bytes()
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sc.GZIPETag = fmt.Sprintf("%x", md5.Sum(sc.GZIPContent))
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}
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return sc, nil
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}
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func (sc *StaticContent) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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gzok := strings.Contains(r.Header.Get("Accept-Encoding"), "gzip")
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gzlen := len(sc.GZIPContent)
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// Use the correct etag
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var localETag string
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if gzok && gzlen > 0 {
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localETag = sc.GZIPETag
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} else {
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localETag = sc.ETag
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}
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// Check the etag, maybe we don't need to send content
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remoteETag := r.Header.Get("If-None-Match")
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if localETag == remoteETag {
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w.WriteHeader(http.StatusNotModified)
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return
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}
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w.Header().Set("ETag", localETag)
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w.Header().Set("Content-Type", sc.Type)
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// Finally, write our content
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if gzok && gzlen > 0 {
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w.Header().Set("Content-Encoding", "gzip")
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w.Header().Set("Content-Length", fmt.Sprintf("%d", gzlen))
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w.Write(sc.GZIPContent)
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} else {
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w.Header().Set("Content-Length", fmt.Sprintf("%d", len(sc.Content)))
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w.Write(sc.Content)
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}
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}
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