[PATCH 4/7] proxy_pass: split out body and trailer reading in response

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

Hopefully this increases readability as well and allows
us to make easier adjustments to support new features in
the future.
---
 lib/yahns/proxy_http_response.rb | 105 +++++++++++++++++++++------------------
 1 file changed, 58 insertions(+), 47 deletions(-)

diff --git a/lib/yahns/proxy_http_response.rb b/lib/yahns/proxy_http_response.rb
index 00915df..52a8aff 100644
--- a/lib/yahns/proxy_http_response.rb
+++ b/lib/yahns/proxy_http_response.rb
@@ -124,63 +124,74 @@ def proxy_res_headers(res)
     [ alive, wbuf, have_body ]
   end
 
+  def proxy_read_body(tip, kcar, req_res, alive, wbuf)
+    chunk = ''.dup if kcar.chunked?
+    len = kcar.body_bytes_left
+    rbuf = Thread.current[:yahns_rbuf]
+
+    case tmp = tip.shift || req_res.kgio_tryread(0x2000, rbuf)
+    when String
+      if len
+        kcar.body_bytes_left -= tmp.size # progress for body_eof? => true
+      elsif chunk
+        kcar.filter_body(chunk, rbuf = tmp) # progress for body_eof? => true
+        next if chunk.empty? # call req_res.kgio_tryread for more
+        tmp = chunk_out(chunk)
+      elsif alive # HTTP/1.0 upstream, HTTP/1.1 client
+        tmp = chunk_out(tmp)
+      # else # HTTP/1.0 upstream, HTTP/1.0 client, do nothing
+      end
+      wbuf = proxy_write(wbuf, tmp, alive)
+      chunk.clear if chunk
+    when nil # EOF
+      # HTTP/1.1 upstream, unexpected premature EOF:
+      return proxy_err_response(nil, req_res, nil, wbuf) if len || chunk
+
+      # HTTP/1.0 upstream:
+      wbuf = proxy_write(wbuf, "0\r\n\r\n".freeze, true) if alive
+      req_res.shutdown
+      break
+    when :wait_readable
+      return wait_on_upstream(req_res, alive, wbuf)
+    end until kcar.body_eof?
+
+    if chunk
+      # tip is an empty array and becomes trailer storage
+      req_res.proxy_trailers = [ rbuf.dup, tip ]
+      return proxy_read_trailers(kcar, req_res, alive, wbuf)
+    end
+    wbuf ? proxy_busy_mod_blocked(wbuf, wbuf.busy) : proxy_busy_mod_done(alive)
+  end
+
+  def proxy_read_trailers(kcar, req_res, alive, wbuf)
+    chunk, tlr = req_res.proxy_trailers
+    rbuf = Thread.current[:yahns_rbuf]
+
+    until kcar.trailers(tlr, chunk)
+      case rv = req_res.kgio_tryread(0x2000, rbuf)
+      when String
+        chunk << rv
+      when :wait_readable
+        return wait_on_upstream(req_res, alive, wbuf)
+      when nil # premature EOF
+        return proxy_err_response(nil, req_res, nil, wbuf)
+      end # no loop here
+    end
+    wbuf = proxy_write(wbuf, trailer_out(tlr), alive)
+    wbuf ? proxy_busy_mod_blocked(wbuf, wbuf.busy) : proxy_busy_mod_done(alive)
+  end
+
   # start streaming the response once upstream is done sending headers to us.
   # returns :wait_readable if we need to read more from req_res
   # returns :ignore if we yield control to the client(self)
   # returns nil if completely done
   def proxy_response_start(res, tip, kcar, req_res)
     alive, wbuf, have_body = proxy_res_headers(res)
-    rbuf = Thread.current[:yahns_rbuf]
     tip = tip.empty? ? [] : [ tip ]
 
     if have_body
       req_res.proxy_trailers = nil # define to avoid uninitialized warnings
-      chunk = ''.dup if kcar.chunked?
-      tlr = nil
-      len = kcar.body_bytes_left
-
-      case tmp = tip.shift || req_res.kgio_tryread(0x2000, rbuf)
-      when String
-        if len
-          kcar.body_bytes_left -= tmp.size # progress for body_eof? => true
-        elsif chunk
-          kcar.filter_body(chunk, rbuf = tmp) # progress for body_eof? => true
-          next if chunk.empty? # read req_res.kgio_tryread for more
-          tmp = chunk_out(chunk)
-        elsif alive # HTTP/1.0 upstream, HTTP/1.1 client
-          tmp = chunk_out(tmp)
-        # else # HTTP/1.0 upstream, HTTP/1.0 client, do nothing
-        end
-        wbuf = proxy_write(wbuf, tmp, alive)
-        chunk.clear if chunk
-      when nil # EOF
-        # HTTP/1.1 upstream, unexpected premature EOF:
-        return proxy_err_response(nil, req_res, nil, wbuf) if len || chunk
-
-        # HTTP/1.0 upstream:
-        wbuf = proxy_write(wbuf, "0\r\n\r\n".freeze, true) if alive
-        req_res.shutdown
-        break
-      when :wait_readable
-        return wait_on_upstream(req_res, alive, wbuf)
-      end until kcar.body_eof?
-
-      if chunk
-        chunk = rbuf
-        req_res.proxy_trailers = [ chunk, tlr = [] ]
-        rbuf = Thread.current[:yahns_rbuf] = ''.dup
-        until kcar.trailers(tlr, chunk)
-          case rv = req_res.kgio_tryread(0x2000, rbuf)
-          when String
-            chunk << rv
-          when :wait_readable
-            return wait_on_upstream(req_res, alive, wbuf)
-          when nil # premature EOF
-            return proxy_err_response(nil, req_res, nil, wbuf)
-          end # no loop here
-        end
-        wbuf = proxy_write(wbuf, trailer_out(tlr), alive)
-      end
+      return proxy_read_body(tip, kcar, req_res, alive, wbuf)
     end
 
     # all done reading response from upstream, req_res will be discarded