Chapter 4 Programming Issues for CINs

Note LabVIEW 4.x stored Boolean arrays in memory as a series of bits packed to

the nearest 16-bit word. LabVIEW 4.x ignored unused bits in the last word. LabVIEW 4.x ordered the bits from left to right; that is, the most significant bit (MSB) is index 0. As with other arrays, a 4-byte dimension size preceded Boolean arrays. The dimension size for LabVIEW 4.x Boolean arrays indicates the number of valid bits contained in the array.

Paths

The exact structure for Path data types is subject to change in future versions of LabVIEW. A Path is a dynamic data structure LabVIEW passes the same way it passes arrays. LabVIEW stores the data for Paths in an application zone handle. Refer to Refer to Chapter 6, Function Descriptions, for more information about the functions that manipulate

Paths.

Clusters Containing Variably Sized Data

For cluster arguments, LabVIEW passes a pointer to a structure containing the elements of the cluster. LabVIEW stores scalar values directly as components inside the structure. If a component is another cluster, LabVIEW stores this cluster value as a component of the main cluster. If a component is an array or string, LabVIEW stores a handle to the array or string component in the structure.

Resizing Arrays and Strings

To resize return arrays and strings you pass to a CIN, use the LabVIEW SetCINArraySize routine. Pass to the function the handle you want to resize, information describing the data structure, and the desired size of the array or handle. The function takes into account any padding and alignment needed for the data structure. However, the function does not update the dimension fields in the array. If you successfully resize the array, you need to update the dimension fields to correctly reflect the number of elements in the array.

You can resize numeric arrays more easily with NumericArrayResize. Pass to this function the array you want to resize, a description of the data structure, and information about the new size of the array.

Chapter 4 Programming Issues for CINs

When you resize arrays of variably sized data (for example, arrays of strings) with the SetCINArraySize or NumericArrayResize routines, consider the following issues:

•If the new size of the array is smaller, LabVIEW disposes of the handles used by the disposed element. Neither function sets the dimension field of the array. You must do this in your code after the function call.

•If the new size of the array is larger, LabVIEW does not automatically create the handles for the new elements. You have to create these handles after the function returns.

The following sections describe the SetCINArraySize and

NumericArrayResize routines.

Chapter 4 Programming Issues for CINs

SetCINArraySize

MgErr SetCINArraySize (UHandle dataH, int32 paramNum, int32 newNumElmts);

Purpose

SetCINArraySize resizes a data handle based on the data structure of an argument you pass to the CIN. It does not set the array dimension field.

Parameters

Return Value

MgErr, which can contain the errors in the following list. Refer to the Manager Overview section later in this chapter for more information about MgErr.

Chapter 4 Programming Issues for CINs

NumericArrayResize

MgErr NumericArrayResize(int32 typeCode, int32 numDims, UHandle *dataHP, int32 totalNewSize);

Purpose

NumericArrayResize resizes a data handle referring to a numeric array. This routine also accounts for alignment issues. It does not set the array dimension field. If *dataHP is NULL, LabVIEW allocates a new array handle in *dataHP.

Parameters

Return Values

MgErr, which can contain the errors in the following list. Refer to the Manager Overview section later in this chapter for more information about MgErr.