status-go/protocol/urls/utils.go

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package urls
import (
"bytes"
"encoding/base64"
"strings"
"unicode/utf8"
"github.com/andybalholm/brotli"
)
const (
htmlTagStart = 60 // Unicode `<`
htmlTagEnd = 62 // Unicode `>`
)
// Taken from https://stackoverflow.com/a/64701836
// Aggressively strips HTML tags from a string.
// It will only keep anything between `>` and `<`.
func stripHTMLTags(s string) string {
// Setup a string builder and allocate enough memory for the new string.
var builder strings.Builder
builder.Grow(len(s) + utf8.UTFMax)
in := false // True if we are inside an HTML tag.
start := 0 // The index of the previous start tag character `<`
end := 0 // The index of the previous end tag character `>`
for i, c := range s {
// If this is the last character and we are not in an HTML tag, save it.
if (i+1) == len(s) && end >= start {
builder.WriteString(s[end:])
}
// Keep going if the character is not `<` or `>`
if c != htmlTagStart && c != htmlTagEnd {
continue
}
if c == htmlTagStart {
// Only update the start if we are not in a tag.
// This make sure we strip out `<<br>` not just `<br>`
if !in {
start = i
}
in = true
// Write the valid string between the close and start of the two tags.
builder.WriteString(s[end:start])
continue
}
// else c == htmlTagEnd
in = false
end = i + 1
}
s = builder.String()
return s
}
func encodeDataURL(data []byte) (string, error) {
bb := bytes.NewBuffer([]byte{})
writer := brotli.NewWriter(bb)
_, err := writer.Write(data)
if err != nil {
return "", err
}
err = writer.Close()
if err != nil {
return "", err
}
return base64.URLEncoding.EncodeToString(bb.Bytes()), nil
}
func decodeDataURL(data string) ([]byte, error) {
decoded, err := base64.URLEncoding.DecodeString(data)
if err != nil {
return nil, err
}
output := make([]byte, 4096)
bb := bytes.NewBuffer(decoded)
reader := brotli.NewReader(bb)
n, err := reader.Read(output)
if err != nil {
return nil, err
}
return output[:n], nil
}