[WIP OPTION #1] fix output buffering with SSL_write

[Eric Wong <e@80x24.org>]

The underlying SSL_write called by the OpenSSL socket when
we use write_nonblock must get the same arguments after a
call returns SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE.

FIXME: this probably breaks badly for embedded strings
(but it's tricky to test...)
---
 lib/yahns/openssl_client.rb      |  5 +++++
 lib/yahns/proxy_http_response.rb |  1 +
 lib/yahns/sendfile_compat.rb     | 23 +++++++++++++++++------
 lib/yahns/wbuf.rb                | 14 +++++++++++++-
 4 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/lib/yahns/openssl_client.rb b/lib/yahns/openssl_client.rb
index bf64255..c5b5c8a 100644
--- a/lib/yahns/openssl_client.rb
+++ b/lib/yahns/openssl_client.rb
@@ -37,6 +37,7 @@ def sync
   def yahns_init_ssl(ssl_ctx)
     @need_accept = true
     @ssl = OpenSSL::SSL::SSLSocket.new(self, ssl_ctx)
+    @ssl_blocked = false
   end
 
   def kgio_trywrite(buf)
@@ -46,6 +47,10 @@ def kgio_trywrite(buf)
     rv
   end
 
+  def kgio_trywritev(buf)
+    abort 'BUG: we cannot use writev with OpenSSL'
+  end
+
   def kgio_syssend(buf, flags)
     kgio_trywrite(buf)
   end
diff --git a/lib/yahns/proxy_http_response.rb b/lib/yahns/proxy_http_response.rb
index 0a7e722..287d039 100644
--- a/lib/yahns/proxy_http_response.rb
+++ b/lib/yahns/proxy_http_response.rb
@@ -11,6 +11,7 @@ module Yahns::HttpResponse # :nodoc:
   # it may return a newly-created wbuf or nil
   def proxy_write(wbuf, buf, alive)
     unless wbuf
+      buf = buf.join if Array === buf && respond_to?(:yahns_init_ssl)
       # no write buffer, try to write directly to the client socket
       case rv = String === buf ? kgio_trywrite(buf) : kgio_trywritev(buf)
       when nil then return # done writing buf, likely
diff --git a/lib/yahns/sendfile_compat.rb b/lib/yahns/sendfile_compat.rb
index 8bd4622..4842cda 100644
--- a/lib/yahns/sendfile_compat.rb
+++ b/lib/yahns/sendfile_compat.rb
@@ -4,21 +4,32 @@
 # frozen_string_literal: true
 
 module Yahns::SendfileCompat # :nodoc:
+  attr_accessor :ssl_blocked
+
   def trysendfile(io, offset, count)
     return 0 if count == 0
-    count = 0x4000 if count > 0x4000
-    buf = Thread.current[:yahns_sfbuf] ||= ''.dup
-    io.pos = offset
-    str = io.read(count, buf) or return # nil for EOF
+
+    if respond_to?(:yahns_init_ssl) && @ssl_blocked
+      str = @ssl_blocked
+      @ssl_blocked = false
+    else
+      count = 0x4000 if count > 0x4000
+      buf = Thread.current[:yahns_sfbuf] ||= ''.dup
+      io.pos = offset
+      str = io.read(count, buf) or return # nil for EOF
+    end
+
     n = 0
     case rv = kgio_trywrite(str)
     when String # partial write, keep trying
-      n += (str.size - rv.size)
+      n += (str.bytesize - rv.size)
       str = rv
     when :wait_writable, :wait_readable
+      @ssl_blocked = str
+      Thread.current[:yahns_sfbuf] = ''.dup
       return n > 0 ? n : rv
     when nil
-      return n + str.size # yay!
+      return n + str.bytesize # yay!
     end while true
   end
 end
diff --git a/lib/yahns/wbuf.rb b/lib/yahns/wbuf.rb
index 1b4ce6e..3dddb95 100644
--- a/lib/yahns/wbuf.rb
+++ b/lib/yahns/wbuf.rb
@@ -48,6 +48,9 @@ def wbuf_writev(buf)
   end
 
   def wbuf_write(c, buf)
+    ssl = c.respond_to?(:yahns_init_ssl)
+    buf = buf.join if ssl && Array === buf
+
     # try to bypass the VFS layer and write directly to the socket
     # if we're all caught up
     case rv = String === buf ? c.kgio_trywrite(buf) : c.kgio_trywritev(buf)
@@ -60,7 +63,16 @@ def wbuf_write(c, buf)
     end until @busy
 
     @tmpio ||= Yahns::TmpIO.new(@tmpdir)
-    @sf_count += String === buf ? @tmpio.write(buf) : wbuf_writev(buf)
+    if @sf_count == 0 && c.respond_to?(:yahns_init_ssl)
+      # We need to maintain a consistent RSTRING_PTR and MRI strings are CoW
+      # XXX: this breaks if we have embedded strings!
+      c.ssl_blocked = buf.dup
+      # we need to maintain placeholder in tmpio so
+      # sf_offset remains consistent for wbuf_flush
+      @sf_count = @tmpio.write(buf)
+    else
+      @sf_count += String === buf ? @tmpio.write(buf) : wbuf_writev(buf)
+    end
 
     # we spent some time copying to the FS, try to write to
     # the socket again in case some space opened up...
-- 
EW