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wire formats in docs clarified

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This commit is contained in:
Martin Sustrik 2010-03-10 12:40:13 +01:00
parent 98801ebcae
commit 8f90ae8dfd
2 changed files with 44 additions and 18 deletions
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40
doc/zmq_pgm.txt
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@ -81,20 +81,42 @@ order specifying either the offset of the first message 'frame' in the datagram
or containing the value 0xFFFF if the datagram contains solely an intermediate
part of a larger message.
A single PGM datagram as used by 0MQ can thus be defined by the following ABNF
grammar:
The payload of a single PGM datagram as used by 0MQ can thus be defined by the
following ABNF grammar:
....
datagram = message / intermediate
message = (frame-offset *data 1*frame) <1>
intermediate = (escape 1*data)
frame-offset = 2OCTET
escape = %xFF %xFF
data = 1*OCTET
datagram = (offset data)
offset = 2OCTET
data = *OCTET
....
<1> 'frame' as defined in linkzmq:zmq_tcp[7].
As already explained above, the data from consecutive datagrams are interpreted
as a bytestream that's parsed according to the grammar described in
linkzmq:zmq_tcp[7].
Each packet thus looks like this:
----
+-----------+------------+------------------+----------------------+
| IP header | PGM header | offset (16 bits) | data |
+-----------+------------+------------------+----------------------+
----
Following example shows how messages are arranged in subsequent packets:
----
+---------------+--------+-----------+-----------------------------+
| PGM/IPheaders | 0x0000 | message 1 | message 2 (part 1) |
+---------------+--------+-----------+-----------------------------+
+---------------+--------+-----------------------------------------+
| PGM/IPheaders | 0xFFFF | message 2 (part 2) |
+---------------+--------+-----------------------------------------+
+---------------+--------+--------------------------+-----------+
| PGM/IPheaders | 0x0008 | message 2 (last 8 bytes) | message 3 |
+---------------+--------+--------------------------+-----------+
----
EXAMPLE
-------

22
doc/zmq_tcp.txt
View File

@ -54,32 +54,35 @@ A 'peer address' may be specified by either of the following:
WIRE FORMAT
-----------
0MQ messages are transmitted over TCP in frames consisting of the message
length followed by the message data. The size of the message data MUST
correspond to the message length. A single 'frame' can be defined by the
length followed by flags byte and the message data. The length MUST correspond
to the length of the remaining part of the frame.
. A single 'frame' can be defined by the
following ABNF grammar:
....
frame = (message-length message-data)
message-length = OCTET / (escape 8OCTET)
frame = (length flags data)
length = OCTET / (escape 8OCTET)
flags = OCTET
escape = %xFF
message-data = *OCTET
data = *OCTET
....
For messages of 0 to 254 octets in length, the message length is represented by
For messages of 0 to 253 octets in length, the message length is represented by
a single octet:
....
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message size | Message body ... |
| Message size | Flags | Message body ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message body ...
+-+-+-+-+-+-+- ...
....
For messages of 255 or more octets in length, the message length is represented
For messages of 254 or more octets in length, the message length is represented
by a single octet with the value `255` followed by the message length
represented as a 64-bit unsigned integer in network byte order:
@ -91,12 +94,13 @@ represented as a 64-bit unsigned integer in network byte order:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message size ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message size | Message body ... |
| Message size | Flags | Message body ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message body ...
+-+-+-+-+-+-+-+ ...
....
The flags field is reserved and MUST be set to 0.
EXAMPLES
--------