ZMQII-26: Use zero-copy for large messages (rx side)

src/decoder.hpp

@@ -22,8 +22,11 @@
 
 #include <stddef.h>
 #include <string.h>
+#include <stdlib.h>
 #include <algorithm>
 
+#include "err.hpp"
+
 namespace zmq
 {
 
@@ -42,31 +45,80 @@ namespace zmq
     {
     public:
 
-        inline decoder_t () :
-            read_ptr (NULL),
+        inline decoder_t (size_t bufsize_) :
+            read_pos (NULL),
             to_read (0),
-            next (NULL)
+            next (NULL),
+            bufsize (bufsize_)
+        {
+            buf = (unsigned char*) malloc (bufsize_);
+            zmq_assert (buf);
+        }
+
+        inline ~decoder_t ()
+        {
+            free (buf);
+        }
+
+        //  Returns a buffer to be filled with binary data.
+        inline void get_buffer (unsigned char **data_, size_t *size_)
         {
+            //  If we are expected to read large message, we'll opt for zero-
+            //  copy, i.e. we'll ask caller to fill the data directly to the
+            //  message. Note that subsequent read(s) are non-blocking, thus
+            //  each single read reads at most SO_RCVBUF bytes at once not
+            //  depending on how large is the chunk returned from here.
+            //  As a consequence, large messages being received won't block
+            //  other engines running in the same I/O thread for excessive
+            //  amounts of time.
+            if (to_read >= bufsize) {
+                *data_ = read_pos;
+                *size_ = to_read;
+                return;
+            }
+
+            *data_ = buf;
+            *size_ = bufsize;
         }
 
-        //  Push the binary data to the decoder. Returns number of bytes
-        // actually parsed.
-        inline size_t write (unsigned char *data_, size_t size_)
+        //  Processes the data in the buffer previously allocated using
+        //  get_buffer function. size_ argument specifies nemuber of bytes
+        //  actually filled into the buffer. Function returns number of
+        //  bytes actually processed.
+        inline size_t process_buffer (unsigned char *data_, size_t size_)
         {
+            //  In case of zero-copy simply adjust the pointers, no copying
+            //  is required. Also, run the state machine in case all the data
+            //  were processed.
+            if (data_ == read_pos) {
+                read_pos += size_;
+                to_read -= size_;
+
+                while (!to_read)
+                    if (!(static_cast <T*> (this)->*next) ())
+                        return size_;
+                return size_;
+            }
+
             size_t pos = 0;
             while (true) {
-                size_t to_copy = std::min (to_read, size_ - pos);
-                if (read_ptr) {
-                    memcpy (read_ptr, data_ + pos, to_copy);
-                    read_ptr += to_copy;
-                }
-                pos += to_copy;
-                to_read -= to_copy;
+
+                //  Try to get more space in the message to fill in.
+                //  If none is available, return.
                 while (!to_read)
                     if (!(static_cast <T*> (this)->*next) ())
                         return pos;
+
+                //  If there are no more data in the buffer, return.
                 if (pos == size_)
                     return pos;
+
+                //  Copy the data from buffer to the message.
+                size_t to_copy = std::min (to_read, size_ - pos);
+                memcpy (read_pos, data_ + pos, to_copy);
+                read_pos += to_copy;
+                pos += to_copy;
+                to_read -= to_copy;
             }
         }
 
@@ -78,20 +130,23 @@ namespace zmq
 
         //  This function should be called from derived class to read data
         //  from the buffer and schedule next state machine action.
-        inline void next_step (void *read_ptr_, size_t to_read_,
+        inline void next_step (void *read_pos_, size_t to_read_,
             step_t next_)
         {
-            read_ptr = (unsigned char*) read_ptr_;
+            read_pos = (unsigned char*) read_pos_;
             to_read = to_read_;
             next = next_;
         }
 
     private:
 
-        unsigned char *read_ptr;
+        unsigned char *read_pos;
         size_t to_read;
         step_t next;
 
+        size_t bufsize;
+        unsigned char *buf;
+
         decoder_t (const decoder_t&);
         void operator = (const decoder_t&);
     };

src/encoder.hpp

@@ -22,8 +22,11 @@
 
 #include <stddef.h>
 #include <string.h>
+#include <stdlib.h>
 #include <algorithm>
 
+#include "err.hpp"
+
 namespace zmq
 {
 
@@ -35,68 +38,81 @@ namespace zmq
     {
     public:
 
-        inline encoder_t ()
+        inline encoder_t (size_t bufsize_) :
+            bufsize (bufsize_)
         {
+            buf = (unsigned char*) malloc (bufsize_);
+            zmq_assert (buf);
         }
 
-        //  The function tries to fill the supplied chunk by binary data.
-        //  If offset is not NULL, it is filled by offset of the first message
-        //  in the batch. If there's no beginning of a message in the batch,
-        //  offset is set to -1. Both data_ and size_ are in/out parameters.
-        //  Upon exit, data_ contains actual position of the data read (may
-        //  be different from the position requested) and size_ contains number
-        //  of bytes actually provided.
-        inline void read (unsigned char **data_, size_t *size_,
+        inline ~encoder_t ()
+        {
+            free (buf);
+        }
+
+        //  The function returns a batch of binary data. If offset is not NULL,
+        //  it is filled by offset of the first message in the batch. If there's
+        //  no beginning of a message in the batch, offset is set to -1.
+        inline void get_buffer (unsigned char **data_, size_t *size_,
             int *offset_ = NULL)
         {
-            int offset = -1;
             size_t pos = 0;
+            if (offset_)
+                *offset_ = -1;
+
+            while (true) {
+
+                //  If there are no more data to return, run the state machine.
+                //  If there are still no data, return what we already have
+                //  in the buffer.
+                if (!to_write) {
+                    if (!(static_cast <T*> (this)->*next) ()) {
+                        *data_ = buf;
+                        *size_ = pos;
+                        return;
+                    }
 
-            while (pos < *size_) {
+                    //  If beginning of the message was processed, adjust the
+                    //  first-message-offset.
+                    if (beginning) { 
+                        if (offset_ && *offset_ == -1)
+                            *offset_ = pos;
+                        beginning = false;
+                    }
+                }
 
-                //  If we are able to fill whole buffer in a single go, let's
-                //  use zero-copy. There's no disadvantage to it as we cannot
-                //  stuck multiple messages into the buffer anyway. Note that
-                //  subsequent write(s) are non-blocking, thus each single
-                //  write writes at most SO_SNDBUF bytes at once not depending
-                //  on how large is the chunk returned from here.
+                //  If there are no data in the buffer yet and we are able to
+                //  fill whole buffer in a single go, let's use zero-copy.
+                //  There's no disadvantage to it as we cannot stuck multiple
+                //  messages into the buffer anyway. Note that subsequent
+                //  write(s) are non-blocking, thus each single write writes
+                //  at most SO_SNDBUF bytes at once not depending on how large
+                //  is the chunk returned from here.
                 //  As a consequence, large messages being sent won't block
                 //  other engines running in the same I/O thread for excessive
                 //  amounts of time.
-                if (pos == 0 && to_write >= *size_) {
+                if (!pos && to_write >= bufsize) {
                     *data_ = write_pos;
-                    write_pos += to_write;
-                    pos = to_write;
+                    *size_ = to_write;
+                    write_pos = NULL;
                     to_write = 0;
-                    break;
+                    return;
                 }
 
-                if (to_write) {
-
-                    size_t to_copy = std::min (to_write, *size_ - pos);
-                    memcpy (*data_ + pos, write_pos, to_copy);
-                    pos += to_copy;
-                    write_pos += to_copy;
-                    to_write -= to_copy;
-                }
-                else {
-                    bool more = (static_cast <T*> (this)->*next) ();
-                    if (beginning && offset == -1) {
-                        offset = pos;
-                        beginning = false;
-                    }
-                    if (!more)
-                        break;
+                //  Copy data to the buffer. If the buffer is full, return.
+                size_t to_copy = std::min (to_write, bufsize - pos);
+                memcpy (buf + pos, write_pos, to_copy);
+                pos += to_copy;
+                write_pos += to_copy;
+                to_write -= to_copy;
+                if (pos == bufsize) {
+                    *data_ = buf;
+                    *size_ = pos;
+                    return;
                 }
             }
-
-            //  Return offset of the first message in the buffer.
-            if (offset_)
-                *offset_ = offset;
-
-            //  Return the size of the filled-in portion of the buffer.
-            *size_ = pos;
         }
+
     protected:
 
         //  Prototype of state machine action.
@@ -121,6 +137,9 @@ namespace zmq
         step_t next;
         bool beginning;
 
+        size_t bufsize;
+        unsigned char *buf;
+
         encoder_t (const encoder_t&);
         void operator = (const encoder_t&);
     };

src/zmq_decoder.cpp

@@ -22,7 +22,8 @@
 #include "wire.hpp"
 #include "err.hpp"
 
-zmq::zmq_decoder_t::zmq_decoder_t () :
+zmq::zmq_decoder_t::zmq_decoder_t (size_t bufsize_) :
+    decoder_t <zmq_decoder_t> (bufsize_),
     destination (NULL)
 {
     zmq_msg_init (&in_progress);

src/zmq_decoder.hpp

@@ -32,7 +32,7 @@ namespace zmq
     {
     public:
 
-        zmq_decoder_t ();
+        zmq_decoder_t (size_t bufsize_);
         ~zmq_decoder_t ();
 
         void set_inout (struct i_inout *destination_);

src/zmq_encoder.cpp

@@ -21,7 +21,8 @@
 #include "i_inout.hpp"
 #include "wire.hpp"
 
-zmq::zmq_encoder_t::zmq_encoder_t () :
+zmq::zmq_encoder_t::zmq_encoder_t (size_t bufsize_) :
+    encoder_t <zmq_encoder_t> (bufsize_),
     source (NULL)
 {
     zmq_msg_init (&in_progress);

src/zmq_encoder.hpp

@@ -32,7 +32,7 @@ namespace zmq
     {
     public:
 
-        zmq_encoder_t ();
+        zmq_encoder_t (size_t bufsize_);
         ~zmq_encoder_t ();
 
         void set_inout (struct i_inout *source_);

src/zmq_engine.cpp

@@ -27,21 +27,15 @@
 zmq::zmq_engine_t::zmq_engine_t (io_thread_t *parent_, fd_t fd_,
       const options_t &options_) :
     io_object_t (parent_),
-    inbuf (NULL),
+    inpos (NULL),
     insize (0),
-    inpos (0),
-    outbuf (NULL),
+    decoder (in_batch_size),
+    outpos (NULL),
     outsize (0),
-    outpos (0),
+    encoder (out_batch_size),
     inout (NULL),
     options (options_)
 {
-    //  Allocate read & write buffer.
-    inbuf_storage = (unsigned char*) malloc (in_batch_size);
-    zmq_assert (inbuf_storage);
-    outbuf_storage = (unsigned char*) malloc (out_batch_size);
-    zmq_assert (outbuf_storage);
-
     //  Initialise the underlying socket.
     int rc = tcp_socket.open (fd_, options.sndbuf, options.rcvbuf);
     zmq_assert (rc == 0);
@@ -49,8 +43,6 @@ zmq::zmq_engine_t::zmq_engine_t (io_thread_t *parent_, fd_t fd_,
 
 zmq::zmq_engine_t::~zmq_engine_t ()
 {
-    free (outbuf_storage);
-    free (inbuf_storage);
 }
 
 void zmq::zmq_engine_t::plug (i_inout *inout_)
@@ -80,13 +72,12 @@ void zmq::zmq_engine_t::unplug ()
 
 void zmq::zmq_engine_t::in_event ()
 {
-    //  If there's no data to process in the buffer, read new data.
-    if (inpos == insize) {
+    //  If there's no data to process in the buffer...
+    if (!insize) {
 
-        //  Read as much data as possible to the read buffer.
-        inbuf = inbuf_storage;
-        insize = tcp_socket.read (inbuf, in_batch_size);
-        inpos = 0;
+        //  Retrieve the buffer and read as much data as possible.
+        decoder.get_buffer (&inpos, &insize);
+        insize = tcp_socket.read (inpos, insize);
 
         //  Check whether the peer has closed the connection.
         if (insize == (size_t) -1) {
@@ -96,15 +87,15 @@ void zmq::zmq_engine_t::in_event ()
         }
     }
 
-    //  Following code should be executed even if there's not a single byte in
-    //  the buffer. There still can be a decoded messages stored in the decoder.
-
     //  Push the data to the decoder.
-    int nbytes = decoder.write (inbuf + inpos, insize - inpos);
+    size_t processed = decoder.process_buffer (inpos, insize);
+
+    //  Adjust the buffer.
+    inpos += processed;
+    insize -= processed;
 
-    //  Adjust read position. Stop polling for input if we got stuck.
-    inpos += nbytes;
-    if (inpos < insize)
+    //  Stop polling for input if we got stuck.
+    if (processed < insize)
         reset_pollin (handle);
 
     //  Flush all messages the decoder may have produced.
@@ -114,31 +105,28 @@ void zmq::zmq_engine_t::in_event ()
 void zmq::zmq_engine_t::out_event ()
 {
     //  If write buffer is empty, try to read new data from the encoder.
-    if (outpos == outsize) {
-
-        outbuf = outbuf_storage;
-        outsize = out_batch_size;
-        encoder.read (&outbuf, &outsize);
-        outpos = 0;
-
+    if (!outsize) {
+        encoder.get_buffer (&outpos, &outsize);
+        
         //  If there is no data to send, stop polling for output.
-        if (outsize == 0)
+        if (outsize == 0) {
             reset_pollout (handle);
+            return;
+        }
     }
 
     //  If there are any data to write in write buffer, write as much as
     //  possible to the socket.
-    if (outpos < outsize) {
-        int nbytes = tcp_socket.write (outbuf + outpos, outsize - outpos);
-
-        //  Handle problems with the connection.
-        if (nbytes == -1) {
-            error ();
-            return;
-        }
+    int nbytes = tcp_socket.write (outpos, outsize);
 
-        outpos += nbytes;
+    //  Handle problems with the connection.
+    if (nbytes == -1) {
+        error ();
+        return;
     }
+
+    outpos += nbytes;
+    outsize -= nbytes;
 }
 
 void zmq::zmq_engine_t::revive ()

src/zmq_engine.hpp

@@ -57,21 +57,16 @@ namespace zmq
         tcp_socket_t tcp_socket;
         handle_t handle;
 
-        unsigned char *inbuf_storage;
-        unsigned char *inbuf;
+        unsigned char *inpos;
         size_t insize;
-        size_t inpos;
+        zmq_decoder_t decoder;
 
-        unsigned char *outbuf_storage;
-        unsigned char *outbuf;
+        unsigned char *outpos;
         size_t outsize;
-        size_t outpos;
+        zmq_encoder_t encoder;
 
         i_inout *inout;
 
-        zmq_encoder_t encoder;
-        zmq_decoder_t decoder;
-
         options_t options;
 
         zmq_engine_t (const zmq_engine_t&);