Two byte alignment issue in the structure #534
Conversation
old code: return (int)numBytes; new code: return (int)Math.Ceiling(numBytes); //For example: 9 bool data, length = 1.125, but actually occupies 2 bytes
| if (count != infos.Count()) { | ||
| if(numBytes % 2 != 0) | ||
| numBytes++;//word align |
There was a problem hiding this comment.
| if (count != infos.Count()) { | |
| if(numBytes % 2 != 0) | |
| numBytes++;//word align | |
| if (count != infos.Count()) | |
| { | |
| if (numBytes % 2 != 0) | |
| numBytes++; //word align |
There was a problem hiding this comment.
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
There was a problem hiding this comment.
The above code has been verified by the project and the test is normal.
There was a problem hiding this comment.
My suggestion is about code style (see the spacing and newline).
| @@ -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 | |||
There was a problem hiding this comment.
| if(numBytes %2 != 0) //word align | |
| if (numBytes %2 != 0) //word align |
There was a problem hiding this comment.
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。
| /// <param name="structType">the type of the struct</param> | ||
| /// <returns>the number of bytes</returns> | ||
| public static int GetStructSize(Type structType) | ||
| /// <summary> |
There was a problem hiding this comment.
Nit: keep the spaces, so undo this change.
| @@ -1,7 +1,7 @@ | |||
| <Project Sdk="Microsoft.NET.Sdk"> | |||
|
|
|||
| <PropertyGroup> | |||
| <TargetFrameworks>net452;net462;netstandard2.0;netstandard1.3;net5.0;net6.0;net7.0</TargetFrameworks> | |||
There was a problem hiding this comment.
I don't know the policy for supporting older targets, but the same could apply to .NET 5 too.
My feeling is that for PLCs quite a lot of older targets are around, because they run and an running system isn't touched (in that area).
So maybe NS 1.3 should be kept too (except everything from these API are covered by net452 or net462 -- which I don't know as NS 1.3 is soo old 😉).
There was a problem hiding this comment.
Sorry, this is not necessary. This happened when I was testing another code and the compilation failed. Later, I forgot to restore it.
No description provided.