// We avoid dependency on the unicode package, but check validity of the implementation
// in the tests.
func isSpace(r rune) bool {
	if r <= '\u00FF' {
		// Obvious ASCII ones: \t through \r plus space. Plus two Latin-1 oddballs.
		switch r {
		case ' ', '\t', '\n', '\v', '\f', '\r':
			return true
		case '\u0085', '\u00A0':
			return true
		}
		return false
	}

package, such as C.puts. It collects all such identifiers. The next
step is to determine each kind of name. In C.xxx the xxx might refer
to a type, a function, a constant, or a global variable. Cgo must
decide which.

The obvious thing for cgo to do is to process the preamble, expanding
#includes and processing the corresponding C code. That would require
a full C parser and type checker that was also aware of any extensions

	f, err := parser.ParseFile(fset, filename, nil, parser.ParseComments)
	if err != nil {
		return nil, err
	}
	parsedFileCache[filename] = f

	return f, nil
}

// Disable before debugging non-obvious errors from the type-checker.
const usePkgCache = true

var (
	pkgCache = map[string]*apiPackage{} // map tagKey to package
	pkgTags  = map[string][]string{}    // map import dir to list of relevant tags
)