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Introduction
------------
Haven't you always wanted to take the contents of a text file and write them to another text file, only backwards? Well, even if you've never even dreamed of doing this, here's your chance. This hack will take any size text file and create a mirror version of it.
To perform this hack, we take advantage of the GetEOF function, to find out how long the file is. We also use the File Set Position command to set the file marker for the source file where we want it to be.
Instructions - Put the module called 'Backwards' in your Module Folder, which is in the same location as the MicroPhone application. If you do not have a Module Folder, create one. Open any MicroPhone settings document. Create the following script:
Set Variable * Backwards from TEXT File Dialog "'File to Convert?'"
If Expression "Length(Backwards) > 0"
Do Script "'Main','Backwards'"
End If
That's it.
Theory
------
So, what's behind this hack? Let's take a quick look at the scripts in Backwards. Here are the scripts in the Backwards module:
Main
Backwards
FileOpen
FileClose
FileReplace
FileInfoGet
FileInfoSet
Main - this script simply calls the script Backwards. It is used to provide a single entry point into the module. This way, you don't have to know the name of a particular script. Just call the main script in any of the modules that have been provided with Open Mike and they will do the right thing.
Backwards - This script does the work of converting the file, by calling several other scripts. First, it calls FileInfoGet to get the type and creator of the source file. Then, it calls FileOpen to open the source and destination files. Next, it repeatedly reads one character from the source file and writes it to the destination file until the entire source file has been processed. Then, it calls FileClose. Finally, it calls FileReplace, to replace the source file with the new file it has created:
If Expression "Exists(Backwards)"
Do Script * "'FileInfoGet'"
If Success
Do Script * "'FileOpen'"
If Success
Dialog Install "'Converting, please wait…'"
Set Variable * Backwardsn from Expression "GetEOF(Backwards)"
While Expression "Backwardsn > 0"
Set Variable * Backwardsn from Expression "Backwardsn - 1"
File * Set Position at Offset "Backwards,Backwardsn"
File * Write "Backwardsb,ReadCh(Backwards)"
End While
Delete Variable Backwardsn
Do Script * "'FileClose'"
Do Script * "'FileInfoSet'"
Do Script * "'FileReplace'"
If Success
Return Success
Else
Remark "--- could not replace old source file"
Return Failure
End If
Else
Remark "--- could not open files"
Do Script * "'FileClose'"
Return Failure
End If
Else
Remark "--- could not get file information"
Return Failure
End If
Else
Remark "--- variable Backwards does not exist"
Return Failure
End If
FileOpen - this script opens the source and destination files. It gives the destination the same name as the source, with '.b' appended to the name. If the name is greater than 31 characters, it concatenates the name until it equals 31 characters. If any problems are encountered, it returns failure. Otherwise, it returns success.
FileClose - this script closes the source and destination files.
FileReplace - this script replaces the old source file with the newly created file. If any problems are encountered, it returns failure. Otherwise, it returns success.
FileInfoGet - this script gets the file information for the source file using the FileTYPE and FileCRTR functions. These values are stored in the variables myFileTYPE and myFileCRTR.
FileInfoSet - this script sets the file information for the new file using the stored TYPE and CREATOR information in the myFileTYPE and myFileCRTR variables.
Where To Go From Here
---------------------
Backwards is an ideal candidate for an XCMD, because all we are dealing with are a source and destination file. MicroPhone scripts are powerful and flexible, but when you need to process a huge file, maybe a 20 megabyte session file from your frenzied weekend, you might find MicroPhone a tad slow. Maybe we'll convert Backwards to an XCMD in a future issue of Open Mike.
Important Note
--------------
Hacks are not guaranteed to work, although there is no reason why they shouldn't work. Every care has been taken to make sure that they work on the hacker's machine, but they may do other things on your machine. Of course, if you encounter problems, you may feel free to tweak the hack to run on your machine.
