Function parse_header

external/httplib.h:4097–4143

template <typename T>
inline bool parse_header(const char *beg, const char *end, T fn) {
  // Skip trailing spaces and tabs.
  while (beg < end && is_space_or_tab(end[-1])) {
    end--;
  }

  auto p = beg;
  while (p < end && *p != ':') {
    p++;
  }

  if (p == end) { return false; }

  auto key_end = p;

  if (*p++ != ':') { return false; }

  while (p < end && is_space_or_tab(*p)) {
    p++;
  }

  if (p < end) {
    auto key_len = key_end - beg;
    if (!key_len) { return false; }

    auto key = std::string(beg, key_end);
    auto val = case_ignore::equal(key, "Location")
                   ? std::string(p, end)
                   : decode_url(std::string(p, end), false);

    // NOTE: From RFC 9110:
    // Field values containing CR, LF, or NUL characters are
    // invalid and dangerous, due to the varying ways that
    // implementations might parse and interpret those
    // characters; a recipient of CR, LF, or NUL within a field
    // value MUST either reject the message or replace each of
    // those characters with SP before further processing or
    // forwarding of that message.
    static const std::string CR_LF_NUL("\r\n\0", 3);
    if (val.find_first_of(CR_LF_NUL) != std::string::npos) { return false; }

    fn(key, val);
    return true;
  }

  return false;
}

inline bool read_headers(Stream &strm, Headers &headers) {
  const auto bufsiz = 2048;