Implement sendmsg/recvmsg for 1.8 using ffi

lib/linux/sendmsg.rb

@@ -0,0 +1,80 @@
+# Patchup to add Socket#sendmsg and Socket#recvmsg for ruby 1.8
+
+if BasicSocket.instance_methods.grep(/^sendmsg$/).empty?
+  require 'ffi'
+
+  class BasicSocket
+    module FFIExt
+      extend FFI::Library
+      ffi_lib FFI::Library::LIBC
+      attach_function :sendmsg, [:int, :buffer_in, :int], :ssize_t
+      attach_function :recvmsg, [:int, :buffer_inout, :int], :ssize_t
+    end
+    
+    class Msghdr < FFI::Struct
+      layout :name, :pointer,
+        :namelen, :socklen_t,
+        :iov, :pointer,
+        :iovlen, :size_t,
+        :control, :pointer,
+        :controllen, :socklen_t,
+        :flags, :int
+    end
+    
+    class IOVec < FFI::Struct
+      layout :base, :pointer,
+        :len, :size_t
+    end
+
+    def sendmsg(mesg, flags=0, dest_sockaddr=nil, *controls)
+      data = FFI::MemoryPointer.new(mesg.bytesize, 1, false)
+      data.put_bytes(0, mesg)
+
+      iov = IOVec.new
+      iov[:base] = data
+      iov[:len] = mesg.bytesize
+      
+      header = Msghdr.new
+      header[:name] = nil     # TODO: dest_sockaddr
+      header[:namelen] = 0    # dest_sockaddr
+      header[:iov] = iov
+      header[:iovlen] = 1
+      header[:control] = nil  # TODO: controls
+      header[:controllen] = 0 # controls
+      header[:flags] = flags
+      
+      Kernel.select(nil, [self])
+      res = FFIExt.sendmsg(fileno, header, flags)
+      raise "sendmsg error: #{res}" if res < 0  # FIXME: read errno
+      # return numbytes_sent
+      res
+    end
+    
+    def recvmsg(maxmesglen=nil, flags=0, maxcontrollen=nil, opts={})
+      data = FFI::MemoryPointer.new(maxmesglen || 4096, 1, false)
+      namebuf = FFI::MemoryPointer.new(64, 1, false)
+      
+      iov = IOVec.new
+      iov[:base] = data
+      iov[:len] = data.size
+      
+      header = Msghdr.new
+      header[:name] = namebuf
+      header[:namelen] = namebuf.size
+      header[:iov] = iov
+      header[:iovlen] = 1
+      header[:flags] = flags
+      
+      Kernel.select([self])
+      res = FFIExt.recvmsg(fileno, header, flags)
+      raise "recvmsg error: #{res}" if res < 0  # FIXME: read errno
+      # return [mesg, sender_addrinfo, rflags, *controls]
+      return [
+        data.get_bytes(0, res),
+        namebuf.get_bytes(0, header[:namelen]),
+        header[:flags]
+        # TODO: controls
+      ]
+    end
+  end
+end