Cap a send() or wolfSSL_read() length at INT_MAX (#2655)

* Cap a send() or wolfSSL_read() length at INT_MAX

On 64-bit Windows SocketStream::write() handed size to send(), whose
length is an int, so a single write of 4 GiB or more went out as its low
32 bits: a 4 GiB + 1 byte write sent one byte, and write_data() then
retried the remaining 4 GiB as zero-byte sends forever. The INT_MAX cap
that read() has was limited to 32-bit Windows in df20c27 (#1294), when
the body was still written with one unchecked write(); write_data() now
sends the rest, so the cap applies to every Windows build again.

The wolfSSL tls::read() had the same cast, so a read into a buffer over
INT_MAX failed. Cap it as the OpenSSL backend has done since f80864c.

* Drop the 4 GiB write test and shorten comments

The Windows-only test allocated 4 GiB and took about 5 s, which is too
heavy for CI.

---------

Co-authored-by: yhirose <yuji.hirose.bug@gmail.com>

httplib.h

@@ -12876,7 +12876,8 @@ inline ssize_t SocketStream::read(char *ptr, size_t size) {
 inline ssize_t SocketStream::write(const char *ptr, size_t size) {
   if (!wait_writable()) { return -1; }
 
-#if defined(_WIN32) && !defined(_WIN64)
+  // Winsock's send() takes an int length, even on 64-bit Windows
+#ifdef _WIN32
   size =
       (std::min)(size, static_cast<size_t>((std::numeric_limits<int>::max)()));
 #endif
@@ -23054,6 +23055,9 @@ inline ssize_t read(session_t session, void *buf, size_t len, TlsError &err) {
   }
 
   auto wsession = static_cast<impl::WolfSSLSession *>(session);
+  constexpr auto max_len =
+      static_cast<size_t>((std::numeric_limits<int>::max)());
+  if (len > max_len) { len = max_len; }
   int ret = wolfSSL_read(wsession->ssl, buf, static_cast<int>(len));
 
   if (ret > 0) {