From 365557f111b453289a5e2ce0cdda0899ae248c71 Mon Sep 17 00:00:00 2001 From: Koichi Sasada Date: Fri, 8 Nov 2019 09:39:28 +0900 Subject: 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. --- io.rb | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 io.rb (limited to 'io.rb') 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 maxlen bytes from ios using + # the read(2) system call after O_NONBLOCK is set for + # the underlying file descriptor. + # + # If the optional outbuf argument is present, + # it must reference a String, which will receive the data. + # The outbuf 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 ios 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 Errno::EBADF. + # + # 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 -- cgit v1.2.3