HTTP reads and writes return bytes transferred (API Change):

* HTTP read and write operations now return the
  number of bytes transferred to or from the stream.

Actions Required:

* Modify HTTP read and/or write completion handlers to receive
  the extra std::size_t bytes_transferred parameter.

example/http/client/async-ssl/http_client_async_ssl.cpp

@@ -125,12 +125,17 @@ public:
             std::bind(
                 &session::on_write,
                 shared_from_this(),
-                std::placeholders::_1));
+                std::placeholders::_1,
+                std::placeholders::_2));
     }
 
     void
-    on_write(boost::system::error_code ec)
+    on_write(
+        boost::system::error_code ec,
+        std::size_t bytes_transferred)
     {
+        boost::ignore_unused(bytes_transferred);
+
         if(ec)
             return fail(ec, "write");
         
@@ -139,12 +144,17 @@ public:
             std::bind(
                 &session::on_read,
                 shared_from_this(),
-                std::placeholders::_1));
+                std::placeholders::_1,
+                std::placeholders::_2));
     }
 
     void
-    on_read(boost::system::error_code ec)
+    on_read(
+        boost::system::error_code ec,
+        std::size_t bytes_transferred)
     {
+        boost::ignore_unused(bytes_transferred);
+
         if(ec)
             return fail(ec, "read");
 

example/http/client/async/http_client_async.cpp

@@ -104,12 +104,17 @@ public:
             std::bind(
                 &session::on_write,
                 shared_from_this(),
-                std::placeholders::_1));
+                std::placeholders::_1,
+                std::placeholders::_2));
     }
 
     void
-    on_write(boost::system::error_code ec)
+    on_write(
+        boost::system::error_code ec,
+        std::size_t bytes_transferred)
     {
+        boost::ignore_unused(bytes_transferred);
+
         if(ec)
             return fail(ec, "write");
         
@@ -118,12 +123,17 @@ public:
             std::bind(
                 &session::on_read,
                 shared_from_this(),
-                std::placeholders::_1));
+                std::placeholders::_1,
+                std::placeholders::_2));
     }
 
     void
-    on_read(boost::system::error_code ec)
+    on_read(
+        boost::system::error_code ec,
+        std::size_t bytes_transferred)
     {
+        boost::ignore_unused(bytes_transferred);
+
         if(ec)
             return fail(ec, "read");
 

example/http/client/crawl/http_crawl.cpp

@@ -297,12 +297,17 @@ public:
             strand_.wrap(std::bind(
                 &worker::on_write,
                 shared_from_this(),
-                std::placeholders::_1)));
+                std::placeholders::_1,
+                std::placeholders::_2)));
     }
 
     void
-    on_write(boost::system::error_code ec)
+    on_write(
+        boost::system::error_code ec,
+        std::size_t bytes_transferred)
     {
+        boost::ignore_unused(bytes_transferred);
+
         if(ec)
         {
             report_.aggregate(
@@ -324,12 +329,17 @@ public:
             strand_.wrap(std::bind(
                 &worker::on_read,
                 shared_from_this(),
-                std::placeholders::_1)));
+                std::placeholders::_1,
+                std::placeholders::_2)));
     }
 
     void
-    on_read(boost::system::error_code ec)
+    on_read(
+        boost::system::error_code ec,
+        std::size_t bytes_transferred)
     {
+        boost::ignore_unused(bytes_transferred);
+
         if(ec)
         {
             report_.aggregate(