Newton 2.x Q&A: Using Strings as Hex Data and Windows NTK

Using Strings as Hex Data and Windows NTK

One of the Newton 2.x OS Q&As
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This document was exported on 7/23/97.

CHANGED: Using Strings as Hex Data and Windows NTK (7/18/97)

Q: When I use SetClass(SetLength("\u<hex data>"), theLength), theClass) in Windows NTK , the binary object is not what I expect. It seems to be byte-swapped. How can I create binary objects with data in them in Windows NTK?

A: In Windows NTK (and other Windows NS environments), strings are stored in byte swapped order, that is, low byte first. This is because strings are basically arrays of 16-bit Unicode characters, and on the Intel platform 16-bit values are most usefully stored low byte first. Technically, changing the class and length of a string relies on the internal representation of strings, which isn't documented or supported, though it works fine on Newton OS and Mac OS platforms.

The correct way to create binary objects is to use the new MakeBinaryFromHex() function; it handles the byte-swapping issues properly. This function is defined by the platform file, and only runs at build-time -- it doesn't exist on the Newton device. You may need to get a newer platform file because this function was added after Windows NTK 1.6 shipped.