Title:           socket.py WHY
Author:          waterapple
Pastebin link:   http://pastebin.com/5T5zAbQL
First Edit:      Monday 30th of March 2015 12:08:01 AM CDT
Last Edit:       Monday 30th of March 2015 12:08:01 AM CDT

    def read(self, size=-1):
        # Use max, disallow tiny reads in a loop as they are very inefficient.
        # We never leave read() with any leftover data from a new recv() call
        # in our internal buffer.
        rbufsize = max(self._rbufsize, self.default_bufsize)
        # Our use of StringIO rather than lists of string objects returned by
        # recv() minimizes memory usage and fragmentation that occurs when
        # rbufsize is large compared to the typical return value of recv().
        buf = self._rbuf
        buf.seek(0, 2)  # seek end
        if size < 0:
            # Read until EOF
            self._rbuf = StringIO()  # reset _rbuf.  we consume it via buf.
            while True:
                try:
                    data = self._sock.recv(rbufsize)
                except error, e:
                    if e.args[0] == EINTR:
                        continue
                    raise
                if not data:
                    break
                buf.write(data)
            return buf.getvalue()
        else:
            # Read until size bytes or EOF seen, whichever comes first
            buf_len = buf.tell()
            if buf_len >= size:
                # Already have size bytes in our buffer?  Extract and return.
                buf.seek(0)
                rv = buf.read(size)
                self._rbuf = StringIO()
                self._rbuf.write(buf.read())
                return rv
 
            self._rbuf = StringIO()  # reset _rbuf.  we consume it via buf.
            while True:
                left = size - buf_len
                # recv() will malloc the amount of memory given as its
                # parameter even though it often returns much less data
                # than that.  The returned data string is short lived
                # as we copy it into a StringIO and free it.  This avoids
                # fragmentation issues on many platforms.
                try:
                    data = self._sock.recv(left)
                except error, e:
                    if e.args[0] == EINTR:
                        continue
                    raise
                if not data:
                    break
                n = len(data)
                if n == size and not buf_len:
                    # Shortcut.  Avoid buffer data copies when:
                    # - We have no data in our buffer.
                    # AND
                    # - Our call to recv returned exactly the
                    #   number of bytes we were asked to read.
                    return data
                if n == left:
                    buf.write(data)
                    del data  # explicit free
                    break
                assert n <= left, "recv(%d) returned %d bytes" % (left, n)
                buf.write(data)
                buf_len += n
                del data  # explicit free
                #assert buf_len == buf.tell()
            return buf.getvalue()