17 Bit Software 2: Collection B

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PRE1 P - C O M P R E S S V2.3 INTRODUCTION P-Compress is a compression/de-compression tool designed to meet the great majority of the requirements of users efficiently and economically while being very easy to use. It will compress single files, drawers or complete disks, preserving disk and drawer structures. Individual files can be joined into a single PACK, similar to an archive and by using PACKs two uncompressed disks will normally fit on one. Drawers and disks can be copied from one place to another, selected files or classes of files being compressed and the remainder just copied. P-Compressed files, including sounds, pictures and animations, can be displayed by P-Reader without prior decompression, and P- Compressed texts can be loaded into and saved from P-Writer. The latest version of P-Reader is being used to display this file. Two important areas not covered at present are: Hard-disk back-up. Use a specialised programme (eg BRU). Self-extracting executables. Use Imploder from Fish 422. One of the main uses of P-Compress may be to reduce the size of your own personal library collection of utilities, data, games, code examples, stored away for occasional reference. By just compressing all data, leaving icons and executables untouched, and using P-Reader as the basic text reader and display tool, my own "library" of 35 disks reduced to 25. Caution is needed when doing this as data files used by the executables must be left unchanged. Alternatively if the P-Suite utility P-Fixlib is to be used (which allows DOS to treat compressed files as though they were uncompressed) the whole disk can be compressed, doubling its capacity. P-Compress employs the latest LZH compression technique using code by Barthel and Krekel, modified to limit memory requirements. This release also includes the small utility P-Unpack, whose sole purpose in life is to unpack Packs. Details are on Page 11. COMPARISON WITH ALTERNATIVE PROGRAMMES Whole disk compression tools: eg LHWARP, Zoom. When used to PACK a complete disk P-Compress only compresses the files on the disk and not such additional data as boot-blocks. As a result output will be smaller than that of true whole-disk tools. P-Unpack can write a standard boot-block to the re-constituted disk. Speed is comparable but memory usage much lower. If you really need to include everything on the disk, Zoom is recommended. Archivers: eg LHArc, PKAZip. To suit their role in the maintenance of archives these include a host of facilities which are of little or no use to most of us. As a result they are not easy to use. One effect of the complexity is that with some combinations of commands and switches files can be lost. (Tip: always use the extended filenames switch) As far as performance goes P-Compress sacrifices about 0.1% in efficiency for the sake of decompression speed and low memory requirement for large files. It is faster and uses less memory than LHArcA and much faster than LHArc. PKAZip is very fast, efficiency usually poorer, memory useage greatly excessive. Large archived collections of files cannot be handled by single-drive Amigas without expansion memory (unless a vast number of disk-swops are acceptable), PACKS can. General compression tools: eg Power Packer An excellent programme in its day the current PD version of PowerPacker is completely outclassed by the new wave of LZH compression tools - although decompression is fast. As far as ease of use is concerned users should form their own judgement. PowerPacker has the ability to create self- extracting executables which P-Compress does not do at present, however Imploder handles this particular job better and more quickly. Some comparative performance figures are given at the end of these instructions. INSTRUCTIONS P-Compress opens a window on Workbench showing: On the left Progress window. Top right Decompress window. Centre right Compress window. Bottom right Execute window. Color selection gadget can be found at the top of the lower right P-Compress logo. Click it to cycle the available color palettes. If you have the Arp library installed the programme will use the Arp File- Requester, otherwise a simple string gadget requester will appear. If you are using the latter to call a drawer the entry must end with a slash /. P-Compress can be started from the cli or by double-clicking its icon. DECOMPRESSION Click From. File requester will come up over the progress window. Enter or select the drawer, or file to be de-compressed. Click OK (or cancel). Selected reference will be shown in the From box. #! 1 42 5 0 decompress.brush Click To. File requester will re-appear. Enter/select a disk, file or drawer as required. If an existing file other than a PACK is selected but a drawer or disk was entered at From, a warning will appear. Otherwise new files will be opened as necessary. A PACK can only be decompressed to a disk or drawer - a file entered at To will be ignored and the programme will look at its path to decide where to place the unpacked output. Compressed files will be decompressed to the indicated location, uncompressed files will be just copied. Name and size of the file being handled appears in the progress window. On completion a summary will appear at the bottom of the Decompress window (except where only a single file has been called). The programme will recognise whether the input is a normal file or a PACK, and will act accordingly. PACK in the execute window need not be switched on. You can decompress back over the original - with the same reference entered at From and To. Sufficient space must be available on the disk to take the file currently being decompressed as well as the original (later deleted). If you run out of disk space before decompression is complete you will be asked to insert a new disk. On completion delete any empty drawers on the disks and transfer icons where necessary. Note that when checking for space no account is taken of whether an existing file is being overwritten. This can mean that the request is made when not strictly needed. Collect the extra file or files on another disk and copy back. Before decompressing compressed files a checksum (CRC) is read and checked - if an error is found an appropriate warning will be given and the offending file passed over. Before an existing file is overwritten you will be asked to OK it. Clicking OVERWRITE in the execute window suspends this feature, which is also suspended when a PACKed file is being decompressed. Click GO in the execute window to start decompression, CANCEL to cancel the process, and QUIT to close down. COMPRESSION Select From and To in turn as before and enter or select the source and destination references. Either a disk, drawer or individual file may be selected. If a disk or drawer is to be compressed click on one or more of the boxes listed below to indicate the types of file to be compressed, the remainder will just be copied. Copied files are not provided with Checksums. #! 1 42 4 0 compress.brush DATA "Project" type data files such as texts, IFF pics, animations etc. ICONS You may want to leave icons uncompressed. EXEC Libraries and all executables. HEXEC Executables are stripped of any debug or symbol hunks. In normal operation these are not needed. If you need to select specific individual files to be compressed or just copied use ASK - the programme will halt at each file and ask for instructions. If HEXEC is selected the stripped file will be put into a temporary file RAM:S. If EXEC is also selected RAM:S will then be compressed to the final destination, otherwise it will be just copied; the sizes of the original file, RAM:S, and the final output will be shown. Normally when compressing a file or drawer each file is transferred to an equivalent place at the output location, new drawers being opened as needed, so that the original structure of drawers and their contents is preserved. Alternately a PACK can be created in which all the files are joined into one compendium file or PACK. An individual checksum is provided for each of the files contained. The name PACK will be appended to any filename that may be inserted at To. On decompression the original structure is re-created. HEXEC is not functional when compressing to a pack. If you run out of disk space before compression is complete you will be asked to insert a new disk (except where a PACK is being made - a file cannot be split between two disks). (But see the comment in the decompress section.) Click OVERWRITE, PACK as necessary, and then GO to start compression. Progress and final summary will be shown as before. EXECUTION Click OVERWRITE if existing files are to be overwritten. CLICK PACK if you wish to put all the individual files into a single PACK. Click GO to start compression or decompression, CANCEL to cancel the process and QUIT to close down. #! 1 42 3 0 exec.brush Note that you may enter the same reference in From and To, allowing the direct replacement of a file by its compressed (or decompressed) image. An intermediate temporary file in RAM is used, which of course means that memory consumption is increased. The original is not overwritten unless the compression or decompression operation returns correctly, however for safety 's sake it is always better to have a backup. COMPARISONS Three files have been used: File 1 is a HAM picture. Length 92872 bytes. File 2 is an executable file. Length 28792 bytes. File 3 was made up by joining a general mixture of texts, executables and icons into a single large file. Length 608440 bytes. Size Compress Decompress File 1 LHArcA 51812 1min.08secs 33secs PowerPacker (fastest) 64412 2min.37secs 17secs PowerPacker (best) 54196 23mins.45secs 16secs PKAZip 53407 45secs 21secs P-Compress 52136 49secs 21secs File 2 LHArcA 15788 26secs 11secs PowerPacker (good) 17122 2min.11 9secs PKAZip 15919 24secs 7secs P-Compress 15816 17secs 8secs File 3 LHArcA and PKAZip failed - out of memory. PowerPacker not tried - out of patience. P-Compress 287372 6m.28 1m.48 In all cases compression/decompression was from disk to RAM: using an Amiga 500 with 1M of memory. P - U N P A C K V1.2 When sending out a disk containing a PACK you will normally include on the disk the means of decoding it. This can of course be P-Compress itself, but the considerably smaller P-Unpack may be used instead. The end result is the same but P-Unpack provides two further advantages: It provides the efficient disk-swopping facilities needed by single-disk -drive Amigas with memory that is not sufficient for the whole pack to be copied to and decompressed from ram. By writing the icon with the ToolType "boot" the decompressed output disk is made bootable. (Not functional for the single-floppy-drive user). P-Unpack is called as the Default Tool of a Project icon for a PACK file. When the icon is clicked the PACK will be decompressed and the original structure of files and drawers copied to a disk. Preparation - Sender The Pack should be created in the normal way with P-Compress. Prepare a PROJECT Icon for the Pack, and write P-Unpack as the Default Tool. Include a path (e.g :c/P-Unpack) if necessary. If the output disk is to be made bootable write the single word boot into the Tool Types space. Include P-Unpack on the disk along with the Pack or Packs. It is a good idea to name the pack "CLICK-ME" or incorporate "click-me" into the icon so that the recipient knows what to do. The recipient should not need any other instructions. Use - Recipient The recipient will boot the received disk normally and faced with an icon that incorporates the instruction Click-me will double-click it. P-Unpack will check the number of floppy drives connected. If there is more than one floppy drive connected a requester will appear asking the user to select one, insert an empty disk, and click go. Once decompression is under way an Abort gadget is added. Clicking on this will stop the programme on completion of the current file. If the pack includes a disk icon, this will be adopted and seen if the disk is removed and re-inserted. If the Tool Type boot was written into the icon the output disk will be bootable. If the expanded PACK is larger than a single disk, a notice will call for a new disk when the first is full. Where P-Unpack finds only one floppy drive a different requester will appear asking the user to insert the source disk and click go. Decompression to RAM will continue for as long as memory is available and the user will then be asked to insert the output disk - ram will be copied to this. Disk swopping will continue until decompression is complete - four or five swops may be needed. No early warning will be given of a full disk, but a new disk can be inserted at any of the disk-swops. The output disk can not be made bootable, otherwise the final result is the same. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ P-Compress and P-Unpack are Freeware. They may be copied and distributed freely and used without charge for non_commercial purposes. Authority for commercial use should be obtained from the author below. No responsibility can be accepted for any loss occasioned by use of these programmes. Comments, suggestions, bug-reports all welcome. Chas A. Wyndham, 1265 Canning Mills Road, Roleystone, WA 6111. Australia