Difference between revisions of "ScriptBasic:UsersGuide 4"

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Latest revision as of 05:52, 7 December 2007

[Contents]

4. Code caching

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4.1. How cache file name is calculated
4.2. Cache handling shortages
4.3. Cache security

The interpreter has to do several things before actually starting the BASIC code. It has to read the file, split it into tokens, analyze the program and build the internal executable format. This takes a lot of time especially for programs longer than a few lines. This can be skipped if the code built up is saved into a file and the file is loaded and run without the recompilation.To save the binary format file after the BASIC program was analyzed and build the `-o' option can be used. To load and run the code the binary file can be used instead of the text file containing the BASIC code. The interpreter automatically recognizes the binary format and does not try to interpret it as BASIC program source. To help the interpreter you can also supply the option `-b' on the command-line that tells the interpreter to believe without checking that the file is binary format of the basic program. This is one solution to speed up execution of the ScriptBasic programs and to avoid recompilation of the code several times. The other method is caching.The configuration file (see section Installation Instructions) may contain a value for the key cache. The value for this key should specify a readily existing directory (do not forget the trailing / or \) where the BASIC interpreter can store the binary format of the code. If there is a valid value specified as cache directory the interpreter checks the cache for an already existing binary format file and if that is newer than the BASIC source it neglects the BASIC source and loads the binary format from the cache.On the other hand whenever a BASIC source code was analyzed and built the resulting binary code is saved into the cache. This method is transparent for the user and significantly speeds up program execution especially for CGI programs that run many times.To avoid cache using you can use the command-line option -n.Caching has some limitation that can result unwanted behavior. Before switching on program code cache, please read the following sections that describe the shortages and the security issues that should be considered.


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