This release was done primarily as a chance to clean up the code (including a re-write in C), fix some bugs leftover from 4.2, and to add some new features that had been requested by its users.
The great bulk of the work was converting the original Pascal code to C. This ended up making code that's a bit more readable as C lets you do things naturally that Pascal balks at. The end result should be a lot more portable as the amount of assembly code was reduced considerably.
The major bug fixes are:
¥ DiskCopy will not allow itself to be used when running on a Radius Rocket with RocketWare. The reason for this is that there are some timing issues when talking back and forth between the floppy disk hardware on the motherboard and code executing on the Rocket (in a NuBus slot). Support for DiskCopy, etc., was supposed to be included in the latest release of RocketWare, but the feature never made it in.
¥ DiskCopy now works correctly with DayStar's Turbo 040 accelerator for the Mac II and IIx. Before, it was failing when making a copy.
¥ (BRC #85856, whk-dc-010) If a disk was inserted or removed while DiskCopy was not the frontmost layer, it wouldn't correctly keep track of what was happening. It should now do so correctly.
¥ (BRC #85857, whk-dc-011) DiskCopy now supports desk accessories.
¥ (BRC #87526, whk-dc-037), (BRC #87527, whk-dc-038), (BRC #87528, whk-dc-039) DiskCopy 4.2 had a problem making copies if VM was turned on. This should work better now.
The following bugs were not fixed:
¥ (BRC #86182, whk-dc-015) DiskCopy reports errors using error numbers rather than verbose messages. This will not be fixed because verbose messages take up lots of RAM, which reduces the amount that's available for copying.
¥ (BRC #86475, whk-dc-021) DiskCopy won't duplicate 7.0 spared disks (i.e., disks with bad blocks).
¥ (BRC #87365, whk-dc-035) DiskCopy doesn't properly unmount MFS disks (400K) under System 6.0.x. This appeared to be a Finder problem.
¥ (BRC #87366, whk-dc-036) When running DiskCopy off a floppy disk, it's possible to erase that boot disk during the copy process when the Finder attempts to mount the duplicate disk.
¥ (BRC #87562, whk-dc-040) If a disk image is selected and "PrintÉ" is selected from the Finder's File menu, DiskCopy is brought to the front but no feedback is provided and nothing happens. This is more than likely due to DiskCopy's lack of a "print" item in the File menu, since you can't print disk images.
The new features are the most interesting part (naturally). There is now support for both compressed image files as well as compressed self-extracting images. The compression algorithm is relatively simple, yet seems to achieve a good compression ratio. This is, of course, highly dependent on what's on the disk; a freshly-initialized high-density disk compresses to around 1K. You'll get better results if you initialize a disk and copy files onto it rather than using a disk that's been written to a number of times since the unused blocks on the disk won't have garbage in them.
The self-extracting image application lets a user generate a duplicate disk from an enclosed image without needing DiskCopy. Also, the application requires a significantly smaller RAM footprint than DiskCopy since it doesn't require the entire image to fit into memory. The tradeoff is that the duplication process is slower, but since most likely a user won't have to make multiple copies of the image, this shouldn't be an undue burden.
Testing issues:
Other than a general pounding to make sure the basic stuff still works OK, I think there are three areas that need special attention.
(1) Make sure the compression works correctly for a variety of disks and images. I've tried it on a number of images as part of the development process, but further testing may yield some problems in special cases. If working from floppies, please be sure to keep the master disks locked so that their contents won't be changed as part of mounting them (and thus change the compression results).
(2) Try out the self-extractor process in a variety of configurations. See that DiskCopy correctly creates the self-extractor application, and that the application can then correctly make a copy of the original floppy disk or image.
(3) See if DiskCopy works correctly with VM turned on and a number of other applications running to increase the chances that some of DiskCopy's application heap will be swapped out to disk. DiskCopy should also be tested on pre-IIci Macs so that some patches it installs on those systems can be checked out as well.
