implemented http server

internal/http/headers.go

@@ -0,0 +1,70 @@
+package http
+
+import (
+	"net/url"
+	sh "serveg/internal/string_helper"
+	"strings"
+)
+
+// ContentDisposition builds a Content-Disposition header value (RFC 6266).
+// dispositionType is "inline" or "attachment".
+// filename is an ASCII fallback for old clients,
+// filename* is the exact UTF-8 name.
+//
+//	ContentDisposition("inline", "отчёт 1.txt") ->
+//	inline; filename="_____ 1.txt"; filename*=UTF-8''%D0%BE%D1%82%D1%87%D1%91%D1%82%201.txt
+func ContentDisposition(dispositionType, fileName string) string {
+	var sb sh.StringBuilder
+	sb.Grow(len(dispositionType) + len(fileName)*4 + 32)
+	sb.AddS(dispositionType)
+	sb.AddS(`; filename="`).AddS(AsciiFallbackName(fileName)).AddB('"')
+	sb.AddS(`; filename*=UTF-8''`).AddS(PercentEncodeHeaderValue(fileName))
+	return sb.StringUnsafe()
+}
+
+// percent-encodes characters that are not allowed in urls
+func PercentEcodeUrl(p string) string {
+	u := url.URL{Path: p}
+	return u.EscapedPath()
+}
+
+// PercentEncodeHeaderValue percent-encodes characters that are not allowed in header values
+func PercentEncodeHeaderValue(s string) string {
+	const hexDigits = "0123456789ABCDEF"
+	var sb sh.StringBuilder
+	sb.Grow(len(s))
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if isAttrChar(c) {
+			sb.AddB(c)
+		} else {
+			sb.AddB('%').AddB(hexDigits[c>>4]).AddB(hexDigits[c&0x0F])
+		}
+	}
+	return sb.StringUnsafe()
+}
+
+// attr-char = ALPHA / DIGIT / "!" / "#" / "$" / "&" / "+" / "-" / "."
+// / "^" / "_" / "`" / "|" / "~"
+func isAttrChar(c byte) bool {
+	switch {
+	case 'a' <= c && c <= 'z', 'A' <= c && c <= 'Z', '0' <= c && c <= '9':
+		return true
+	}
+	return strings.IndexByte("!#$&+-.^_`|~", c) >= 0
+}
+
+// AsciiFallbackName replaces each character that can't be safely put
+// in a quoted-string with '_'. One '_' per character, not per byte.
+func AsciiFallbackName(s string) string {
+	var sb sh.StringBuilder
+	sb.Grow(len(s))
+	// range over string iterates runes, invalid UTF-8 gives utf8.RuneError
+	for _, r := range s {
+		if r < 0x20 || r >= 0x7F || r == '"' || r == '\\' || r == '%' {
+			r = '_'
+		}
+		sb.AddB(byte(r))
+	}
+	return sb.StringUnsafe()
+}