socket: allow explicit buffer for recv and recv_nonblock

This reduces GC overhead and makes the API more consistent
with IO#read and IO#read_nonblock.

* ext/socket/basicsocket.c (bsock_recv): document outbuf
* ext/socket/unixsocket.c (unix_recvfrom): ditto
* ext/socket/init.c (rsock_strbuf, recvfrom_locktmp): new functions
  (rsock_s_recvfrom): support destination buffer as 3rd arg
  (rsock_s_recvfrom_nonblock): ditto
* string.c (rb_str_locktmp_ensure): export for internal ext
* test/socket/test_nonblock.rb: test recv_nonblock
* test/socket/test_unix.rb: test recv
  [ruby-core:69543] [Feature #11242]

Benchmark results:

             user     system      total        real
alloc    0.130000   0.280000   0.410000 (  0.420656)
extbuf   0.100000   0.220000   0.320000 (  0.318708)

-------------------8<--------------------
require 'socket'
require 'benchmark'
nr = 100000
msg = ' ' * 16384
size = msg.bytesize
buf = ' ' * size
UNIXSocket.pair(:DGRAM) do |a, b|
  Benchmark.bmbm do |x|
    x.report('alloc') do
      nr.times do
        b.send(msg, 0)
        a.recv(size, 0)
      end
    end

    x.report('extbuf') do
      nr.times do
        b.send(msg, 0)
        a.recv(size, 0, buf)
      end
    end
  end
end

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50912 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 4 insertions, 1 deletions

diff --git a/ext/socket/unixsocket.c b/ext/socket/unixsocket.c
index 9a4c2cfc01..9003529042 100644
--- a/ext/socket/unixsocket.c
+++ b/ext/socket/unixsocket.c
@@ -131,7 +131,7 @@ unix_path(VALUE sock)
 
 /*
  * call-seq:
- *   unixsocket.recvfrom(maxlen [, flags]) => [mesg, unixaddress]
+ *   unixsocket.recvfrom(maxlen [, flags[, outbuf]) => [mesg, unixaddress]
  *
  * Receives a message via _unixsocket_.
  *
@@ -139,6 +139,9 @@ unix_path(VALUE sock)
  *
  * _flags_ should be a bitwise OR of Socket::MSG_* constants.
  *
+ * _outbuf_ will contain only the received data after the method call
+ * even if it is not empty at the beginning.
+ *
  *   s1 = Socket.new(:UNIX, :DGRAM, 0)
  *   s1_ai = Addrinfo.unix("/tmp/sock1")
  *   s1.bind(s1_ai)