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Two byte alignment issue in the structure #534

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Two byte alignment issue in the structure #534

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e69ba85
Code error for calculating structure length
fxyc87 Jul 17, 2024
4b6ec7a
Two byte alignment issue in the structure
fxyc87 Jul 17, 2024
8d95d45
NetStandard1.3 is no longer supported. Support for enumeration types …
fxyc87 Jul 18, 2024
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17 changes: 12 additions & 5 deletions S7.Net/Types/Struct.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,10 +24,11 @@ public static int GetStructSize(Type structType)
#else
.GetFields();
#endif

foreach (var info in infos)
int count = 0;
foreach (var info in infos)
{
switch (info.FieldType.Name)
count++;
switch (info.FieldType.Name)
{
case "Boolean":
numBytes += 0.125;
Expand Down Expand Up @@ -75,11 +76,15 @@ public static int GetStructSize(Type structType)
break;
default:
numBytes += GetStructSize(info.FieldType);
if (count != infos.Count()) {
if(numBytes % 2 != 0)
numBytes++;//word align
Comment on lines +83 to +85
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Suggested change
if (count != infos.Count()) {
if(numBytes % 2 != 0)
numBytes++;//word align
if (count != infos.Count())
{
if (numBytes % 2 != 0)
numBytes++; //word align

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In a block of the PLC, two structures A and B are defined. Structure A occupies 3-byte space, and structure B also occupies 3-byte space. However, in reality, structure B starts from the fourth byte because the PLC is two-byte aligned internally.

当在PLC一个块中，定义一个结构体A，B，其中A占用3个字节空间，B也占3个字节空间，但实际上B是从第4字节开始的，因为PLC内部是两字节对齐的。
将以上翻译为英文

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The above code has been verified by the project and the test is normal.

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My suggestion is about code style (see the spacing and newline).

}
break;
}
}
return (int)numBytes;
}
return (int)Math.Ceiling(numBytes); //For example: 9 bool data, length = 1.125, but actually occupies 2 bytes
}

/// <summary>
/// Creates a struct of a specified type by an array of bytes.
Expand Down Expand Up @@ -238,6 +243,8 @@ public static int GetStructSize(Type structType)
Buffer.BlockCopy(bytes, (int)Math.Ceiling(numBytes), buffer, 0, buffer.Length);
info.SetValue(structValue, FromBytes(info.FieldType, buffer));
numBytes += buffer.Length;
if(numBytes %2 != 0) //word align
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Suggested change
if(numBytes %2 != 0) //word align
if (numBytes %2 != 0) //word align

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When no user-defined structure is in a block of the PLC, there are no such problems. When a structure exists, there is a two-byte alignment issue.

当在PLC一个块中没有自定义结构体时，这些没有问题，当有结构体存在时，就有2字节对齐问题。

numBytes++;
break;
}
}
Expand Down