Check and Create MD5 Checksum Files
checkMD5sums checks the files against a file
the name of an installed package
the path to the top-level directory of an installed package.
MD5 which is created is in a format which can be
md5sum -c MD5 if a suitable command-line version
md5sum is available. (For Windows, one is supplied in
the bundle at https://cran.r-project.org/bin/windows/Rtools.)
dir is missing, an installed package of name
is searched for.
The private function
tools:::.installMD5sums is used to create
MD5 files in the Windows build.
checkMD5sums returns a logical,
NA if there is no
MD5 file to be checked.