140 lines
4.5 KiB
Plaintext
140 lines
4.5 KiB
Plaintext
|
|
linebuf - a dbuf replacement for the New World Order(tm)
|
|
|
|
By Adrian Chadd <adrian@creative.net.au>
|
|
|
|
$Id: linebuf.txt 6 2005-09-10 01:02:21Z nenolod $
|
|
|
|
|
|
History
|
|
-------
|
|
|
|
I could probably learn the dbuf history, but basically its evil. The
|
|
general idea is that a dbuf holds incoming and outgoing data streams.
|
|
The trouble is that well.. it was evil. You can check it out by getting
|
|
the old src/dbuf.c and include/dbuf.h files if you really want.
|
|
|
|
|
|
Replacement
|
|
-----------
|
|
|
|
The linebuf system is a replacement for the dbuf code. The general idea here
|
|
is that the data should be buffered in "lines" rather than just linearly
|
|
like in the dbuf code. This lends to easier manipulation at a later date
|
|
(think flushing data lines to a socket, and even "sharing" linebufs to
|
|
reduce the copying required for one to many delivery.)
|
|
|
|
The linebuf system is broken into two structures, the buf_head and buf_line .
|
|
buf_head contains the buffer information (queue head/tail, length, allocated
|
|
length and the write offset for flushing), and buf_line contains the
|
|
line buffer information (buffer and various flags.)
|
|
|
|
linebuf->terminated is *only* set when a CR/LF combination is received.
|
|
|
|
linebuf->overflow is set if we get more data than we should, and we simply
|
|
truncate the incoming data.
|
|
|
|
linebuf->flushing is set when we are currently writing the buffer. We should
|
|
_NEVER_ be appending to a buffer which we're flushing!
|
|
|
|
When you get a buffer through linebuf_get() or write one through
|
|
linebuf_flush(), it will *always* be terminated with a CR/LF (and a NUL if
|
|
its a linebuf_get()).
|
|
|
|
|
|
Linebuf manipulation
|
|
--------------------
|
|
|
|
To use a linebuf, you simply stick a buf_head_t in your structure somewhere.
|
|
You then use the following routines:
|
|
|
|
int
|
|
linebuf_parse(buf_head_t *bufhead, char *buf, int len)
|
|
|
|
Parse the given buf. This routine does some complex manipulation:
|
|
|
|
- if there is an incomplete buffer at the tail, buf is parsed to try and
|
|
fill that incomplete buffer
|
|
- a buffer is completed by a CR/LF/CRLF/LFCR. It accepts everything purely
|
|
because I wanted to be "liberal in what you accept" ..
|
|
- If a buffer is terminated, the linebuf is flagged terminated
|
|
- If more data is trying to be squeezed into the buffer than space LEFT
|
|
in the buffer, we skip to the next "CRLF", and tag the buffer terminated
|
|
_and_ overflowed.
|
|
- We treat multiple runs of CR/LF/CRLF/LFCR as a single CRLF. This is just
|
|
a little extra goody to stop people sending hundreds of "CRLF"s and creating
|
|
unnecessary buffers.
|
|
- The number of lines parsed is returned (so you can implement per-line flood
|
|
protection ..)
|
|
|
|
|
|
void
|
|
linebuf_put(buf_head_t *bufhead, char *buf, int len)
|
|
|
|
Parse the given buf, ASSUMING it is a single buffer line. This is useful
|
|
for server-generated messages where you know you have a single line, and
|
|
you don't want to go through the overhead of parsing the data just for
|
|
this.
|
|
|
|
|
|
int
|
|
linebuf_get(buf_head_t *bufhead, char *buf, int maxlen)
|
|
|
|
Get a single line from the buffer. This removes data from the head of the
|
|
buffer. If the first buffer is empty or is not terminated, 0 is returned
|
|
which indicates that there is no data to parse. Terminated buffers are
|
|
returned (CR/LF/NUL), and the length INCLUDING the CR/LF/NUL is returned.
|
|
The buffer is copied and the linebuf is then deallocated.
|
|
|
|
|
|
int
|
|
linebuf_flush(int fd, buf_head_t *bufhead)
|
|
|
|
Attempt to flush some data to the given socket. bufhead->writeofs tracks
|
|
where in the head buffer we currently are. If the buffer is not terminated,
|
|
-1 is returned with errno == EWOULDBLOCK to simulate a "retry me" condition.
|
|
(See TODO..)
|
|
|
|
linebuf_flush() returns whatever write() returns, and sets (ie doesn't touch
|
|
after write()) errno accordingly.
|
|
|
|
|
|
int
|
|
linebuf_len(buf_head_t *bufhead)
|
|
|
|
Return the length of the buffer, in bytes. This should be used when calculating
|
|
how big a buffer is for statistics.
|
|
|
|
|
|
int
|
|
linebuf_alloclen(buf_head_t *bufhead)
|
|
|
|
Return how big the *allocated* space is. This is much more suitable for
|
|
anti-flood checking, as someone might be sending a whole bunch of 1-byte
|
|
linebufs which might not trigger a recvq / sendq limit but might chew up
|
|
way too much memory.
|
|
|
|
|
|
|
|
Notes
|
|
-----
|
|
|
|
* Remember that the trailing NUL isn't covered in the string length.
|
|
|
|
|
|
Limitations
|
|
-----------
|
|
|
|
* all the buffers are a fixed size - here they are current 513 bytes
|
|
(510 bytes + CR/LF/NUL)
|
|
|
|
|
|
TODO
|
|
----
|
|
|
|
* linebuf_flush() should be changed a little so if the buffer isn't
|
|
terminated, we *dont* retry flushing a buffer until we get more data.
|
|
|
|
* Implement a reference-friendly linebuf to reduce copies ..
|
|
|