Initial commit

lib/jsmodbus/handler/server/ReadInputRegisters.js

@@ -0,0 +1,52 @@
+'use strict';
+
+const Stampit = require('stampit');
+const Put     = require('put');
+
+module.exports = Stampit()
+    .init(function () {
+        const FC = 4;
+        let init = () => {
+            this.log.debug('initiating read input registers request handler.');
+            this.responseDelay = this.responseDelay || 0;
+            this.setRequestHandler(FC, onRequest);
+        };
+    
+        let _onRequest = (pdu, cb) => {
+            this.log.debug('handling read input registers request.');
+            if (pdu.length !== 5) {
+                cb(Put().word8(0x84).word8(0x02).buffer());
+            } else {
+                const fc          = pdu.readUInt8(0);
+                const start       = pdu.readUInt16BE(1);
+                const byteStart   = start * 2;
+                const quantity    = pdu.readUInt16BE(3);
+
+                this.emit('readInputRegistersRequest', byteStart, quantity);
+
+                let mem = this.getInput();
+
+                if (!quantity || byteStart + (quantity * 2) > mem.length) {
+                    cb(Put().word8(0x84).word8(0x02).buffer());
+                } else {
+                    let response = Put().word8(0x04).word8(quantity * 2);
+
+                    for (let i = byteStart; i < byteStart + (quantity * 2); i += 2) {
+                        response.word16be(mem.readUInt16BE(i));
+                    }
+
+                    cb(response.buffer());
+                }
+            }
+        };
+
+        let onRequest = (pdu, cb) => {
+            if (this.responseDelay) {
+                setTimeout(_onRequest, this.responseDelay, pdu, cb);
+            } else {
+                setImmediate(_onRequest, pdu, cb);
+            }
+        };
+
+        init();
+    });