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Calculate PDU size constraints

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This commit is contained in:
Michael Croes
2018-06-22 20:49:12 +02:00
parent 47cce5887d
commit 2a4485941f
3 changed files with 37 additions and 14 deletions
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29
S7.Net/PLC.cs
View File

@@ -1,5 +1,8 @@
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Sockets;
using S7.Net.Types;
namespace S7.Net
@@ -178,6 +181,25 @@ namespace S7.Net
}
}
private void AssertPduSizeForRead(ICollection<DataItem> dataItems)
{
// 12 bytes of header data, 12 bytes of parameter data for each dataItem
if ((dataItems.Count + 1) * 12 > MaxPDUSize) throw new Exception("Too many vars requested for read");
// 14 bytes of header data, 4 bytes of result data for each dataItem and the actual data
if (GetDataLength(dataItems) + dataItems.Count * 4 + 14 > MaxPDUSize) throw new Exception("Too much data requested for read");
}
private void AssertPduSizeForWrite(ICollection<DataItem> dataItems)
{
// 12 bytes of header data, 18 bytes of parameter data for each dataItem
if (dataItems.Count * 18 + 12 > MaxPDUSize) throw new Exception("Too many vars supplied for write");
// 12 bytes of header data, 16 bytes of data for each dataItem and the actual data
if (GetDataLength(dataItems) + dataItems.Count * 16 + 12 > MaxPDUSize)
throw new Exception("Too much data supplied for write");
}
private void ConfigureConnection()
{
if (tcpClient == null)
@@ -189,6 +211,13 @@ namespace S7.Net
tcpClient.SendTimeout = WriteTimeout;
}
private int GetDataLength(IEnumerable<DataItem> dataItems)
{
// Odd length variables are 0-padded
return dataItems.Select(di => VarTypeToByteLength(di.VarType, di.Count))
.Sum(len => (len & 1) == 1 ? len + 1 : len);
}
#region IDisposable Support
private bool disposedValue = false; // To detect redundant calls

11
S7.Net/PlcAsynchronous.cs
View File

@@ -205,15 +205,10 @@ namespace S7.Net
/// <param name="dataItems">List of dataitems that contains the list of variables that must be read. Maximum 20 dataitems are accepted.</param>
public async Task<List<DataItem>> ReadMultipleVarsAsync(List<DataItem> dataItems)
{
int cntBytes = dataItems.Sum(dataItem => VarTypeToByteLength(dataItem.VarType, dataItem.Count));
//TODO: Figure out how to use MaxPDUSize here
//Snap7 seems to choke on PDU sizes above 256 even if snap7
//replies with bigger PDU size in connection setup.
if (dataItems.Count > 20)
throw new Exception("Too many vars requested");
if (cntBytes > 222)
throw new Exception("Too many bytes requested"); // TODO: proper TDU check + split in multiple requests
AssertPduSizeForRead(dataItems);
try
{
// first create the header
@@ -410,6 +405,8 @@ namespace S7.Net
/// <returns>Task that completes when response from PLC is parsed.</returns>
public async Task WriteAsync(params DataItem[] dataItems)
{
AssertPduSizeForWrite(dataItems);
var message = new ByteArray();
var length = S7WriteMultiple.CreateRequest(message, dataItems);
await stream.WriteAsync(message.Array, 0, length).ConfigureAwait(false);

11
S7.Net/PlcSynchronous.cs
View File

@@ -374,6 +374,8 @@ namespace S7.Net
/// <param name="dataItems">The DataItem(s) to write to the PLC.</param>
public void Write(params DataItem[] dataItems)
{
AssertPduSizeForWrite(dataItems);
var message = new ByteArray();
var length = S7WriteMultiple.CreateRequest(message, dataItems);
stream.Write(message.Array, 0, length);
@@ -479,15 +481,10 @@ namespace S7.Net
/// <param name="dataItems">List of dataitems that contains the list of variables that must be read. Maximum 20 dataitems are accepted.</param>
public void ReadMultipleVars(List<DataItem> dataItems)
{
int cntBytes = dataItems.Sum(dataItem => VarTypeToByteLength(dataItem.VarType, dataItem.Count));
//TODO: Figure out how to use MaxPDUSize here
//Snap7 seems to choke on PDU sizes above 256 even if snap7
//replies with bigger PDU size in connection setup.
if (dataItems.Count > 20)
throw new Exception("Too many vars requested");
if (cntBytes > 222)
throw new Exception("Too many bytes requested"); // TODO: proper TDU check + split in multiple requests
AssertPduSizeForRead(dataItems);
try
{
// first create the header