[cfe-dev] libclang source location from buffer index

[Douglas Gregor]

On Oct 15, 2010, at 6:05 AM, David Chisnall wrote:

> Hi,
> 
> When interacting with the libclang stuff for an in-memory file, it seems quite common not to have the line and column indexes.  I've added a function for generating locations from simple offsets into a file, but I'm not overly familiar with the SourceLocation stuff, so it might not be the most sensible way of doing it.  I have two questions:
> 
> - Does anyone object to this interface?

Nope, it looks good. The patch needs updates to clang-c/Index.h and the exports file, of course :)

> - Is this implementation sane?

Yes, but please check for offset >= the size of the file and that Start is not invalid, so that this routine returns clang_getNullLocation() rather than a potentially-invalid location. libclang needs to be resilient to API use errors.

	- Doug

> David
> 
> -- Sent from my Cray X1
> 
> Index: CIndex.cpp
> ===================================================================
> --- CIndex.cpp	(revision 116439)
> +++ CIndex.cpp	(working copy)
> @@ -2270,6 +2270,22 @@
>   return cxloc::translateSourceLocation(CXXUnit->getASTContext(), SLoc);
> }
> 
> +CXSourceLocation clang_getLocationForOffset(CXTranslationUnit tu,
> +                                            CXFile file,
> +                                            unsigned offset) {
> +  if (!tu || !file)
> +    return clang_getNullLocation();
> +  
> +  ASTUnit *CXXUnit = static_cast<ASTUnit *>(tu);
> +  SourceLocation Start 
> +    = CXXUnit->getSourceManager().getLocation(
> +                                        static_cast<const FileEntry *>(file),
> +                                              1, 1);
> +  SourceLocation SLoc = Start.getFileLocWithOffset(offset);
> +
> +  return cxloc::translateSourceLocation(CXXUnit->getASTContext(), SLoc);
> +}
> +
> CXSourceRange clang_getNullRange() {
>   CXSourceRange Result = { { 0, 0 }, 0, 0 };
>   return Result;
> 
> 
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