Initial import

private/hash.rkt

@@ -0,0 +1,20 @@
+#lang racket/base
+
+(require openssl/sha1
+         openssl/md5)
+
+(provide file-digest)
+
+(define (digest->string v)
+  (cond [(bytes? v) (bytes->hex-string v)]
+        [(string? v) v]
+        [else (format "~a" v)]))
+
+(define (file-digest path [algorithm "sha256"])
+  (define alg (string-downcase (format "~a" algorithm)))
+  (call-with-input-file path
+    (lambda (in)
+      (cond [(member alg '("sha256" "sha-256" "sha2")) (digest->string (sha256-bytes in))]
+            [(member alg '("md5")) (digest->string (md5 in))]
+            [else (error 'file-digest "unsupported digest algorithm: ~a" algorithm)]))
+    #:mode 'binary))