DataBuffer on Loupe Documentation

Usage

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Installation

lpm install databuffer

DataBuffer depends only on sys_lib, which ships with Automation Studio.

Declaration

Declare one datbufBuffer_typ variable per buffer, as a task or global variable. The examples on this page use the following variables; other application variables are left undeclared.

C

datbufBuffer_typ myBuf;
UINT status;

ST

VAR
	myBuf : datbufBuffer_typ;
	status : UINT;
END_VAR

Initialization

A buffer must be initialized with datbufInitBuffer before any other function is called on it. Initialization allocates maxLength bytes of memory for the buffer’s data and clears it to zero.

Functions

Mon, 01 Jan 0001 00:00:00 +0000

All functions take the buffer by address in pBuffer and return a UINT status: 0 on success, otherwise a DATBUF_ERR_enum value.

datbufInitBuffer

Initializes a buffer. All members of the buffer are reset, maxLength bytes of memory are allocated for the data with TMP_alloc, and the new memory is zeroed.

Direction	Name	Type	Description
In	pBuffer	UDINT	Address of the `datbufBuffer_typ` to initialize
In	maxLength	UDINT	Size of the data storage to allocate, in bytes. Must be greater than `0`.
Return	status	UINT	`0` on success, otherwise a `DATBUF_ERR_enum` value

Error	Cause
DATBUF_ERR_INVALIDINPUT	`pBuffer` is `0`, or `maxLength` is `0`
DATBUF_ERR_MEMALLOC	The memory could not be allocated

Call this function once per buffer, in the _INIT routine. TMP_alloc may only be called in _INIT or _EXIT, so this function must not be called cyclically. The library does not free the allocated memory, so calling it again on a buffer that is already initialized allocates a new block and the old one stays allocated until the controller restarts. B&R notes that allocations larger than about 70,000 bytes can cause cycle time violations in task class 1.

Types and Enums

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datbufBuffer_typ

A data buffer. Declare one variable of this type per buffer and pass its address to the library functions. The members are maintained by the library; read them, but do not write them directly.

Name	Type	Description
pData	UDINT	Address of the buffer’s data storage. `0` until the buffer is initialized.
currentLength	UDINT	Number of bytes of data currently in the buffer
maxLength	UDINT	Size of the data storage in bytes, as passed to `datbufInitBuffer`

DATBUF_ERR_enum

Status values returned by the library functions. A return value of 0 means success.