Initial commit of LineBuffer

lib/nntp/tiny/buffer.py

@@ -0,0 +1,68 @@
+class BufferOverflow(Exception):
+    def __init__(self):
+        super().__init__("Buffer overflow")
+
+class LineBuffer():
+    __slots__ = 'buf', 'offset',
+
+    BUFFER_SIZE = 4096
+
+    def __init__(self, size: int=BUFFER_SIZE):
+        self.buf:    bytearray = bytearray(size)
+        self.offset: int = 0
+
+    def readline(self, sock: socket.socket) -> bytes:
+        while True:
+            #
+            # Check and see if there is already a line in the
+            # internal buffer.
+            #
+            offset = self.buf.find(b'\n', self.offset, self.count)
+
+            if offset < 0:
+                #
+                # There is no line in the buffer.  Check and see if
+                # there is more room in the buffer to continue
+                # reading.
+                #
+                if offset == self.BUFFER_SIZE - 1:
+                    #
+                    # There is no room left in the buffer; the line
+                    # must be too long.  Panic.
+                    #
+                    raise BufferOverflow()
+
+                #
+                # Read from the socket to attempt to fill the buffer
+                # more.
+                #
+                data = sock.recv(self.BUFFER_SIZE - self.offset)
+
+                #
+                # Check to see if recv() returned any data.  If not,
+                # the socket is closed.  Return an empty string.
+                #
+                if data == b'':
+                    return ''
+
+                count = len(data)
+
+                #
+                # Now, fill the buffer.  The next iteration of the
+                # loop will be used to check for a newline.
+                #
+                self.buf[self.offset:self.offset+count] = data
+            else:
+                #
+                # There is a line in the buffer.  Prepare to return
+                # it.
+                #
+                ret = self.buf[self.offset:offset]
+
+                #
+                # Advance the offset to one character beyond the
+                # newline.
+                #
+                self.offset = offset + 1
+
+                return str(ret, 'ascii')