Define IO#read/write_nonblock with builtins.

IO#read/write_nonblock methods are defined in prelude.rb with
special private method __read/write_nonblock to reduce keyword
parameters overhead. We can move them into io.rb with builtin
functions.

1 files changed, 123 insertions, 0 deletions

diff --git a/io.rb b/io.rb
new file mode 100644
index 0000000000..1b6dddf9e5
--- /dev/null
+++ b/io.rb
@@ -0,0 +1,123 @@
+class IO
+  # other IO methods are defined in io.c
+
+  # call-seq:
+  #    ios.read_nonblock(maxlen [, options])              -> string
+  #    ios.read_nonblock(maxlen, outbuf [, options])      -> outbuf
+  #
+  # Reads at most <i>maxlen</i> bytes from <em>ios</em> using
+  # the read(2) system call after O_NONBLOCK is set for
+  # the underlying file descriptor.
+  #
+  # If the optional <i>outbuf</i> argument is present,
+  # it must reference a String, which will receive the data.
+  # The <i>outbuf</i> will contain only the received data after the method call
+  # even if it is not empty at the beginning.
+  #
+  # read_nonblock just calls the read(2) system call.
+  # It causes all errors the read(2) system call causes: Errno::EWOULDBLOCK, Errno::EINTR, etc.
+  # The caller should care such errors.
+  #
+  # If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN,
+  # it is extended by IO::WaitReadable.
+  # So IO::WaitReadable can be used to rescue the exceptions for retrying
+  # read_nonblock.
+  #
+  # read_nonblock causes EOFError on EOF.
+  #
+  # On some platforms, such as Windows, non-blocking mode is not supported
+  # on IO objects other than sockets. In such cases, Errno::EBADF will
+  # be raised.
+  #
+  # If the read byte buffer is not empty,
+  # read_nonblock reads from the buffer like readpartial.
+  # In this case, the read(2) system call is not called.
+  #
+  # When read_nonblock raises an exception kind of IO::WaitReadable,
+  # read_nonblock should not be called
+  # until io is readable for avoiding busy loop.
+  # This can be done as follows.
+  #
+  #   # emulates blocking read (readpartial).
+  #   begin
+  #     result = io.read_nonblock(maxlen)
+  #   rescue IO::WaitReadable
+  #     IO.select([io])
+  #     retry
+  #   end
+  #
+  # Although IO#read_nonblock doesn't raise IO::WaitWritable.
+  # OpenSSL::Buffering#read_nonblock can raise IO::WaitWritable.
+  # If IO and SSL should be used polymorphically,
+  # IO::WaitWritable should be rescued too.
+  # See the document of OpenSSL::Buffering#read_nonblock for sample code.
+  #
+  # Note that this method is identical to readpartial
+  # except the non-blocking flag is set.
+  #
+  # By specifying a keyword argument _exception_ to +false+, you can indicate
+  # that read_nonblock should not raise an IO::WaitReadable exception, but
+  # return the symbol +:wait_readable+ instead. At EOF, it will return nil
+  # instead of raising EOFError.
+  def read_nonblock(len, buf = nil, exception: true)
+    __builtin_io_read_nonblock(len, buf, exception)
+  end
+
+  # call-seq:
+  #    ios.write_nonblock(string)   -> integer
+  #    ios.write_nonblock(string [, options])   -> integer
+  #
+  # Writes the given string to <em>ios</em> using
+  # the write(2) system call after O_NONBLOCK is set for
+  # the underlying file descriptor.
+  #
+  # It returns the number of bytes written.
+  #
+  # write_nonblock just calls the write(2) system call.
+  # It causes all errors the write(2) system call causes: Errno::EWOULDBLOCK, Errno::EINTR, etc.
+  # The result may also be smaller than string.length (partial write).
+  # The caller should care such errors and partial write.
+  #
+  # If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN,
+  # it is extended by IO::WaitWritable.
+  # So IO::WaitWritable can be used to rescue the exceptions for retrying write_nonblock.
+  #
+  #   # Creates a pipe.
+  #   r, w = IO.pipe
+  #
+  #   # write_nonblock writes only 65536 bytes and return 65536.
+  #   # (The pipe size is 65536 bytes on this environment.)
+  #   s = "a" * 100000
+  #   p w.write_nonblock(s)     #=> 65536
+  #
+  #   # write_nonblock cannot write a byte and raise EWOULDBLOCK (EAGAIN).
+  #   p w.write_nonblock("b")   # Resource temporarily unavailable (Errno::EAGAIN)
+  #
+  # If the write buffer is not empty, it is flushed at first.
+  #
+  # When write_nonblock raises an exception kind of IO::WaitWritable,
+  # write_nonblock should not be called
+  # until io is writable for avoiding busy loop.
+  # This can be done as follows.
+  #
+  #   begin
+  #     result = io.write_nonblock(string)
+  #   rescue IO::WaitWritable, Errno::EINTR
+  #     IO.select(nil, [io])
+  #     retry
+  #   end
+  #
+  # Note that this doesn't guarantee to write all data in string.
+  # The length written is reported as result and it should be checked later.
+  #
+  # On some platforms such as Windows, write_nonblock is not supported
+  # according to the kind of the IO object.
+  # In such cases, write_nonblock raises <code>Errno::EBADF</code>.
+  #
+  # By specifying a keyword argument _exception_ to +false+, you can indicate
+  # that write_nonblock should not raise an IO::WaitWritable exception, but
+  # return the symbol +:wait_writable+ instead.
+  def write_nonblock(buf, exception: true)
+    __builtin_io_write_nonblock(buf, exception)
+  end
+end