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86 lines (80 loc) · 3.1 KB
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'use strict';
const baEnum = require('./enum');
const DefaultBACnetPort = 47808;
module.exports.encode = (buffer, func, msgLength, originatingIP) => {
buffer[0] = baEnum.BVLL_TYPE_BACNET_IP;
buffer[1] = func;
buffer[2] = (msgLength & 0xFF00) >> 8;
buffer[3] = (msgLength & 0x00FF) >> 0;
if (originatingIP) {
// This is always a FORWARDED_NPDU regardless of the 'func' parameter.
if (func !== baEnum.BvlcResultPurpose.FORWARDED_NPDU) {
throw new Error('Cannot specify originatingIP unless ' +
'BvlcResultPurpose.FORWARDED_NPDU is used.');
}
// Encode the IP address and optional port into bytes.
const [ipstr, portstr] = originatingIP.split(':');
const port = parseInt(portstr) || DefaultBACnetPort;
const ip = ipstr.split('.');
buffer[4] = parseInt(ip[0]);
buffer[5] = parseInt(ip[1]);
buffer[6] = parseInt(ip[2]);
buffer[7] = parseInt(ip[3]);
buffer[8] = (port & 0xFF00) >> 8;
buffer[9] = (port & 0x00FF) >> 0;
return 6 + baEnum.BVLC_HEADER_LENGTH;
} else {
if (func === baEnum.BvlcResultPurpose.FORWARDED_NPDU) {
throw new Error('Must specify originatingIP if ' +
'BvlcResultPurpose.FORWARDED_NPDU is used.');
}
}
return baEnum.BVLC_HEADER_LENGTH;
};
module.exports.decode = (buffer, offset) => {
let len;
const func = buffer[1];
const msgLength = (buffer[2] << 8) | (buffer[3] << 0);
if (buffer[0] !== baEnum.BVLL_TYPE_BACNET_IP || buffer.length !== msgLength) return;
let originatingIP = null;
switch (func) {
case baEnum.BvlcResultPurpose.BVLC_RESULT:
case baEnum.BvlcResultPurpose.ORIGINAL_UNICAST_NPDU:
case baEnum.BvlcResultPurpose.ORIGINAL_BROADCAST_NPDU:
case baEnum.BvlcResultPurpose.DISTRIBUTE_BROADCAST_TO_NETWORK:
case baEnum.BvlcResultPurpose.REGISTER_FOREIGN_DEVICE:
case baEnum.BvlcResultPurpose.READ_FOREIGN_DEVICE_TABLE:
case baEnum.BvlcResultPurpose.DELETE_FOREIGN_DEVICE_TABLE_ENTRY:
case baEnum.BvlcResultPurpose.READ_BROADCAST_DISTRIBUTION_TABLE:
case baEnum.BvlcResultPurpose.WRITE_BROADCAST_DISTRIBUTION_TABLE:
case baEnum.BvlcResultPurpose.READ_BROADCAST_DISTRIBUTION_TABLE_ACK:
case baEnum.BvlcResultPurpose.READ_FOREIGN_DEVICE_TABLE_ACK:
len = 4;
break;
case baEnum.BvlcResultPurpose.FORWARDED_NPDU:
// Work out where the packet originally came from before the BBMD
// forwarded it to us, so we can tell the BBMD where to send any reply to.
const port = (buffer[8] << 8) | buffer[9];
originatingIP = buffer.slice(4, 8).join('.');
// Only add the port if it's not the usual one.
if (port !== DefaultBACnetPort) {
originatingIP += ':' + port;
}
len = 10;
break;
case baEnum.BvlcResultPurpose.SECURE_BVLL:
// unimplemented
return;
default:
return;
}
return {
len: len,
func: func,
msgLength: msgLength,
// Originating IP is set to the IP address of the node that originally
// sent the packet, when it has been forwarded to us by a BBMD (since the
// BBMD's IP address will be in the sender field.
originatingIP: originatingIP,
};
};