IDL_MEMINT and IDL_FILEINT Types

Some of the IDL-supported operating systems limit memory and file lengths to a signed 32-bit integer (approximately 2.3 GB). Some systems have 64-bit memory capabilities and others allow files longer than 2³¹-1 bytes despite being 32-bit memory limited. To gracefully handle these differences without using conditional code, IDL internals use two special types, IDL_TYP_MEMINT (data type IDL_MEMINT) and IDL_TYP_FILEINT (data type IDL_FILEINT) to represent memory and file length limits.

IDL_MEMINT and IDL_FILEINT are not separate and distinct types; they are actually mappings to the IDL types discussed in Mapping of Basic Types. Specifically, they will be IDL_LONG for 32-bit quantities, and IDL_LONG64 for 64-bit quantities.

As an IDL internals programmer, you should not write code that depends on the actual machine type represented by these abstract types. To ensure that your code runs properly on all systems, use IDL_MEMINT and IDL_FILEINT in place of more specific types. These types can be used anywhere that a normal IDL type can be used, such as in keyword processing. Their systematic use for these purposes will ensure that your code is correct on any IDL platform.

Programmers should be aware of the IDL_MEMINTScalar() and IDL_FILEINTScalar() functions, described in Converting Arguments to C Scalars.