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Merge pull request #290 from scamille/fb-AdjustDataItemsPduCheck

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Adjust AssertPduSize checks for Reading multiple DataItems.
This commit is contained in:
Michael Croes
2020-09-04 21:39:55 +02:00
committed by GitHub
parent c99c3d745a eca2ed6474
commit b16097092b
3 changed files with 11 additions and 11 deletions
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12
S7.Net/PLC.cs
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@@ -183,11 +183,13 @@ 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");
// send request limit: 19 bytes of header data, 12 bytes of parameter data for each dataItem
var requiredRequestSize = 19 + dataItems.Count * 12;
if (requiredRequestSize > MaxPDUSize) throw new Exception($"Too many vars requested for read. Request size ({requiredRequestSize}) is larger than protocol limit ({MaxPDUSize}).");
// response limit: 14 bytes of header data, 4 bytes of result data for each dataItem and the actual data
var requiredResponseSize = GetDataLength(dataItems) + dataItems.Count * 4 + 14;
if (requiredResponseSize > MaxPDUSize) throw new Exception($"Too much data requested for read. Response size ({requiredResponseSize}) is larger than protocol limit ({MaxPDUSize}).");
}
private void AssertPduSizeForWrite(ICollection<DataItem> dataItems)

4
S7.Net/PlcAsynchronous.cs
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@@ -209,9 +209,9 @@ namespace S7.Net
/// You have to create and pass a list of DataItems and you obtain in response the same list with the values.
/// Values are stored in the property "Value" of the dataItem and are already converted.
/// If you don't want the conversion, just create a dataItem of bytes.
/// DataItems must not be more than 20 (protocol restriction) and bytes must not be more than 200 + 22 of header (protocol restriction).
/// The number of DataItems as well as the total size of the requested data can not exceed a certain limit (protocol restriction).
/// </summary>
/// <param name="dataItems">List of dataitems that contains the list of variables that must be read. Maximum 20 dataitems are accepted.</param>
/// <param name="dataItems">List of dataitems that contains the list of variables that must be read.</param>
public async Task<List<DataItem>> ReadMultipleVarsAsync(List<DataItem> dataItems)
{
//Snap7 seems to choke on PDU sizes above 256 even if snap7

6
S7.Net/PlcSynchronous.cs
View File

@@ -500,13 +500,11 @@ namespace S7.Net
/// You have to create and pass a list of DataItems and you obtain in response the same list with the values.
/// Values are stored in the property "Value" of the dataItem and are already converted.
/// If you don't want the conversion, just create a dataItem of bytes.
/// DataItems must not be more than 20 (protocol restriction) and bytes must not be more than 200 + 22 of header (protocol restriction).
/// The number of DataItems as well as the total size of the requested data can not exceed a certain limit (protocol restriction).
/// </summary>
/// <param name="dataItems">List of dataitems that contains the list of variables that must be read. Maximum 20 dataitems are accepted.</param>
/// <param name="dataItems">List of dataitems that contains the list of variables that must be read.</param>
public void ReadMultipleVars(List<DataItem> dataItems)
{
//Snap7 seems to choke on PDU sizes above 256 even if snap7
//replies with bigger PDU size in connection setup.
AssertPduSizeForRead(dataItems);
var stream = GetStreamIfAvailable();