[fpc-devel] File search

[Hans-Peter Diettrich]

IMO the file search performance can be improved, in detail for files to 
compile.

Currently FileExists is called for every possible directory, name case 
and possible extensions. This means that the OS may have to search the 
same directory multiple times, for all these cases - O(n). This can be 
reduced to one search, when the (possible) filenames are matched in one 
FindFirst/FindNext run - O(1).

For compiler purposes we IMO can assume that only the file extension can 
be unknown (.pp, .pas...), so that wildcard handling can be reduced to 
an match of the name, followed by an match with the list of possible 
extensions.

Further optimizations can be applied to specialized FindFirst/FindNext 
implementations, by dropping everything not related to filename matching 
(get file attributes, file times...).


Has something like this already been tested? I've seen that compiler 
directory caching is disabled - for what reason?

I'll try to implement and test the simple case (case insensitive Windows 
filesystems). The procedures for case sensitive filesystems will be a 
bit harder to implement, of course.

Any comments are welcome :-)

DoDi