+(defun hash-file (hash file context)
+ "Hash the FILE using the OpenSSL HASH function, returning an octet string.
+
+ CONTEXT is a temporary-files context."
+ (let ((temp (temporary-file context "hash")))
+ (run-program (list "openssl" "dgst" (concatenate 'string "-" hash))
+ :input file :output temp)
+ (with-open-file (in temp)
+ (let ((line (read-line in)))
+ (assert (and (>= (length line) 9)
+ (string= line "(stdin)= " :end1 9)))
+ (decode-hex line :start 9)))))
+