[functional-tests] factor out temp-file library

functional-tests/temp-file.scm

@@ -0,0 +1,26 @@
+(library
+  (temp-file)
+
+  (export
+    temp-file
+    temp-file-containing)
+
+  (import (rnrs)
+          (fmt fmt))
+
+  (define temp-file
+    (let ((counter 0))
+     (lambda ()
+       (let loop ()
+        (let ((path (fmt #f (cat (dsp "/tmp/thinp-functional-tests-")
+                                 (pad-char #\0 (pad/left 4 (num counter)))))))
+          (set! counter (+ counter 1))
+          (if (file-exists? path) (loop) path))))))
+
+  ;; Creates a temporary file with the specified contents.
+  (define (temp-file-containing contents)
+    (let ((path (temp-file)))
+     (with-output-to-file path (lambda () (put-string (current-output-port) contents)))
+     path))
+
+  )