Initial commit of Ccnet server.

python/ccnet/packet.py

@@ -0,0 +1,129 @@
+#coding: UTF-8
+
+"""
+Packet level protocol of ccnet.
+
+About various types of id:
+
+  - A slave processor's id has its highest bit set; a master processor has its highest bit clear
+  - The <id> field of a ccnet packet always has its highest bit clear. The
+    <type> field of the packet determines what type of the packet is (a
+    request, a response, or an update)
+"""
+
+import logging
+import struct
+
+from ccnet.utils import recvall, sendall, NetworkError
+
+REQUEST_ID_MASK = 0x7fffffff
+SLAVE_BIT_MASK = 0x80000000
+
+CCNET_MSG_OK        = 0
+CCNET_MSG_HANDSHAKE = 1
+CCNET_MSG_REQUEST   = 2
+CCNET_MSG_RESPONSE  = 3
+CCNET_MSG_UPDATE    = 4
+CCNET_MSG_RELAY     = 5
+
+def to_request_id(id):
+    return id & REQUEST_ID_MASK
+
+to_response_id = to_request_id
+to_update_id = to_request_id
+to_master_id = to_request_id
+to_packet_id = to_request_id
+
+def to_slave_id(id):
+    return id | SLAVE_BIT_MASK
+
+def to_print_id(id):
+    if id & SLAVE_BIT_MASK:
+        return -to_request_id(id)
+    else:
+        return id
+
+# the byte sequence of ccnet packet header
+CCNET_HEADER_FORMAT = '>BBHI'
+# Number of bytes for the header 
+CCNET_HEADER_LENGTH = struct.calcsize(CCNET_HEADER_FORMAT)
+
+CCNET_MAX_PACKET_LENGTH = 65535
+
+class PacketHeader(object):
+    def __init__(self, ver, ptype, length, id):
+        self.ver = ver
+        self.ptype = ptype
+        self.length = length
+        self.id = id
+
+    def to_string(self):
+        return struct.pack(CCNET_HEADER_FORMAT, self.ver, self.ptype, self.length, self.id)
+
+    def __str__(self):
+        return "<PacketHeader: type = %d, length = %d, id = %u>" % (self.ptype, self.length, self.id)
+
+class Packet(object):
+    version = 1
+    def __init__(self, header, body):
+        self.header = header
+        self.body = body
+
+def parse_header(buf):
+    try:
+        ver, ptype, length, id = struct.unpack(CCNET_HEADER_FORMAT, buf)
+    except struct.error, e:
+        raise NetworkError('error when unpack packet header: %s' % e)
+    
+    return PacketHeader(ver, ptype, length, id)
+
+def format_response(code, code_msg, content):
+    body = code
+    if code_msg:
+        body += " " + code_msg
+    body += "\n"
+
+    if content:
+        body += content
+
+    return body
+
+format_update = format_response
+
+def request_to_packet(id, buf):
+    hdr = PacketHeader(1, CCNET_MSG_REQUEST, len(buf), to_request_id(id))
+    return Packet(hdr, buf)
+
+def response_to_packet(id, code, code_msg, content):
+    body = format_response(code, code_msg, content)
+    hdr = PacketHeader(1, CCNET_MSG_RESPONSE, len(body), to_response_id(id))
+    return Packet(hdr, body)
+
+def update_to_packet(id, code, code_msg, content):
+    body = format_update(code, code_msg, content)
+    hdr = PacketHeader(1, CCNET_MSG_UPDATE, len(body), to_update_id(id))
+    return Packet(hdr, body)
+
+def read_packet(fd):
+    hdr = recvall(fd, CCNET_HEADER_LENGTH)
+    if len(hdr) == 0:
+        logging.warning('connection to daemon is lost')
+        raise NetworkError('Connection to daemon is lost')
+    elif len(hdr) < CCNET_HEADER_LENGTH:
+        raise NetworkError('Only read %d bytes header, expected 8' % len(hdr))
+
+    header = parse_header(hdr)
+
+    if header.length == 0:
+        body = ''
+    else:
+        body = recvall(fd, header.length)
+        if len(body) < header.length:
+            raise NetworkError('Only read %d bytes body, expected %d' % (len(body), header.length))
+
+    return Packet(header, body)
+
+def write_packet(fd, packet):
+    hdr = packet.header.to_string()
+    sendall(fd, hdr)
+    sendall(fd, packet.body)