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I have a Interface Method defined with following inputs.
VAR_INPUT
//receive buffer
pbyRxBuffer : POINTER TO BYTE;
//size of the receive buffer
udiRxBufferSize : UDINT;
END_VAR
For eg: If i get udiRxBufferSize = 10, then i copy 10 bytes through pointers
Now I am relying on udiRxBufferSize for the actual size of buffer. but what if i get a wrong input from user?? He says 10 bytes, but doesnt actually provide the required size.
Can i somehow check the size of actual variable which is provided in pbyRxBuffer??
Also, i have a query for adding pointers
when I do pbyRxBuffer := pbyRxBuffer+1; codesys always incrents 1 pointer by 1 byte only.(irrespective of whether it is defined as POINTER TO BYTE or POINTER TO ULINT)
is my observation correct??
I was expecting that if the pointer is POINTER TO ULINT, it shoul increase by 1 ULINT
Note : I cannot change the interface
Last edit: codesystart 2021-04-18
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Type safety of pointer.
I do not know of a way to do that without changing the interface to, for example, REFERENCE TO ARRAY [*] OF BYTE;
Incrementing POINTER TO ULINT.
Pointers are always to a byte address. So as you said, puliVar + 1 would now be pointing to a ULINT which overlaps the old one.
If you want to reference a ULINT which is 8bytes after your puliVar, you can use puliVar[1]. The online help for pointer probably explains it more clearly https://help.codesys.com/webapp/_cds_datatype_pointer;product=codesys;version=3.5.16.0
Hello
I have a Interface Method defined with following inputs.
VAR_INPUT
//receive buffer
pbyRxBuffer : POINTER TO BYTE;
//size of the receive buffer
udiRxBufferSize : UDINT;
END_VAR
For eg: If i get udiRxBufferSize = 10, then i copy 10 bytes through pointers
Now I am relying on udiRxBufferSize for the actual size of buffer. but what if i get a wrong input from user?? He says 10 bytes, but doesnt actually provide the required size.
Can i somehow check the size of actual variable which is provided in pbyRxBuffer??
Also, i have a query for adding pointers
when I do pbyRxBuffer := pbyRxBuffer+1; codesys always incrents 1 pointer by 1 byte only.(irrespective of whether it is defined as POINTER TO BYTE or POINTER TO ULINT)
is my observation correct??
I was expecting that if the pointer is POINTER TO ULINT, it shoul increase by 1 ULINT
Note : I cannot change the interface
Last edit: codesystart 2021-04-18
Type safety of pointer.
I do not know of a way to do that without changing the interface to, for example, REFERENCE TO ARRAY [*] OF BYTE;
Incrementing POINTER TO ULINT.
Pointers are always to a byte address. So as you said, puliVar + 1 would now be pointing to a ULINT which overlaps the old one.
If you want to reference a ULINT which is 8bytes after your puliVar, you can use puliVar[1]. The online help for pointer probably explains it more clearly https://help.codesys.com/webapp/_cds_datatype_pointer;product=codesys;version=3.5.16.0
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Talk.ru: 1
Ok Thankyou for the info.
I guess we cant really do type safety of pointers...
The second part wont cause much issues. I think i can manage it in my code...