stcp: ed25519 pubkey exchange in handshake, fix instance destroy segfault, fix chat_tcp_test

- u_async.c: process immediate_queue BEFORE epoll_wait in uasync_poll
- stcp_link.c: defensive NULL etcp_conn/etcp_link in stcp_link_close
- utun_instance.c: move stcp_server_list_destroy_all to Phase J (before ETCP),
  add deferred drain in both Phase J and L
- stcp.h/c: STCP_HS_ENC_CLIENT 6→38, STCP_HS_ENC_SERVER 7→39,
  exchange ed25519_pubkey in both handshake directions
- etcp_connections.c: copy peer_ed25519 from STCP to ETCP_CONN in
  etcp_link_enter_ready_tcp; guard link->etcp in tcp_link_close_cb
- chat_sync.c: fix lk->conn NULL dereference for TCP links
- test_stcp.c: update stcp_server_create/stcp_client_connect callsites
- tools/chat_tcp_test: change transport udp→tcp

tools/chatgui/zxing-cpp/core/src/TextEncoder.cpp

@@ -0,0 +1,71 @@
+/*
+* Copyright 2016 Nu-book Inc.
+*/
+// SPDX-License-Identifier: Apache-2.0
+
+#include "TextEncoder.h"
+
+#include "CharacterSet.h"
+#include "ECI.h"
+#include "Utf.h"
+#include "ZXAlgorithms.h"
+#include "Version.h"
+
+#ifdef ZXING_USE_ZINT
+#include <zint.h>
+#else
+#include "libzueci/zueci.h"
+#endif
+
+#include <stdexcept>
+
+namespace ZXing {
+
+void TextEncoder::GetBytes(const std::string& str, CharacterSet charset, std::string& bytes)
+{
+	int eci = ToInt(ToECI(charset));
+	const int str_len = narrow_cast<int>(str.length());
+	int eci_len;
+
+	if (eci == -1)
+		eci = 899; // Binary
+
+	bytes.clear();
+
+#ifdef ZXING_USE_ZINT
+	int error_number = ZBarcode_Dest_Len_ECI(eci, reinterpret_cast<const unsigned char *>(str.data()), str_len, &eci_len);
+	if (error_number >= ZINT_ERROR) // Shouldn't happen
+		throw std::logic_error("Internal error `ZBarcode_Dest_Len_ECI()`");
+
+	bytes.resize(eci_len); // Sufficient but approximate length
+
+	error_number = ZBarcode_UTF8_To_ECI(eci,reinterpret_cast<const unsigned char *>(str.data()), str_len,
+										reinterpret_cast<unsigned char *>(bytes.data()), &eci_len);
+	if (error_number >= ZINT_ERROR) {
+		bytes.clear();
+		throw std::invalid_argument("Unexpected charcode");
+	}
+#else
+	int error_number = zueci_dest_len_eci(eci, reinterpret_cast<const unsigned char *>(str.data()), str_len, &eci_len);
+	if (error_number >= ZUECI_ERROR) // Shouldn't happen
+		throw std::logic_error("Internal error `zueci_dest_len_eci()`");
+
+	bytes.resize(eci_len); // Sufficient but approximate length
+
+	error_number = zueci_utf8_to_eci(eci, reinterpret_cast<const unsigned char *>(str.data()), str_len,
+									 reinterpret_cast<unsigned char *>(bytes.data()), &eci_len);
+	if (error_number >= ZUECI_ERROR) {
+		bytes.clear();
+		throw std::invalid_argument("Unexpected charcode");
+	}
+#endif // ZXING_USE_ZINT
+
+	bytes.resize(eci_len); // Actual length
+}
+
+void TextEncoder::GetBytes(const std::wstring& str, CharacterSet charset, std::string& bytes)
+{
+	GetBytes(ToUtf8(str), charset, bytes);
+}
+
+} // ZXing