Merge pull request #618 from sdilts/fopen-safe

Add open-file function

core/Core.carp

@@ -31,8 +31,8 @@
 (load "Array.carp")
 (load "Char.carp")
 (load "String.carp")
-(load "IO.carp")
 (load "System.carp")
+(load "IO.carp")
 (load "Pattern.carp")
 (load "Debug.carp")
 (load "Pointer.carp")

core/IO.carp

@@ -24,8 +24,17 @@
   (register exit (Fn [Int] a))
   (register EOF Char)
   (doc EOF "the End-Of-File character as a literal.")
-  (doc fopen "opens a file by name using a mode (one or multiple of [r]ead, [w]rite, and [a]ppend), returns a file pointer.")
+  (doc fopen "opens a file by name using a mode (one or multiple of [r]ead, [w]rite, and [a]ppend), returns a file pointer. Consider using the function open-file instead.")
   (register fopen (Fn [&String &String] (Ptr FILE)))
+
+  (doc open-file "opens a file by name using a mode (one or multiple of [r]ead, [w]rite, and [a]ppend), returns a Result type that contains an error string or a file pointer.")
+  (defn open-file [filename mode]
+    (let [ptr (IO.fopen filename mode)]
+      (if (null? ptr)
+        (do
+          (Result.Error System.errno))
+        (Result.Success ptr))))
+
   (doc fclose "closes a file pointer.")
   (register fclose (Fn [(Ptr FILE)] ()))
   (doc fgetc "gets a character from a file pointer.")
@@ -51,15 +60,15 @@
 
   (doc read->EOF "reads a file given by name until the End-Of-File character is reached.")
   (defn read->EOF [filename]
-    (let [f (IO.fopen filename "rb")]
-      (if (null? f)
-        (Result.Error (fmt "File “%s” couldn’t be opened!" filename))
-        (let [c (zero)
-              r []]
-          (do
-            (while (do (set! c (IO.fgetc f))
-                       (/= c IO.EOF))
-              (set! r (Array.push-back r c)))
-            (IO.fclose f)
-            (Result.Success (String.from-chars &r)))))))
+    (let [maybe (IO.open-file filename "rb")]
+      (match maybe
+        (Result.Error x) (Result.Error x)
+        (Result.Success f) (let [c (zero)
+                                 r []]
+                             (do
+                               (while (do (set! c (IO.fgetc f))
+                                          (/= c IO.EOF))
+                                 (set! r (Array.push-back r c)))
+                               (IO.fclose f)
+                               (Result.Success (String.from-chars &r)))))))
 )

core/System.carp

@@ -1,4 +1,5 @@
 (system-include "carp_system.h")
+(system-include "errno.h")
 
 (defmodule System
   (doc free "Frees an object. Should not be called except in direst circumstances.")
@@ -28,4 +29,24 @@
   (register signal-segv Int "SIGSEGV")
   (register signal-term Int "SIGTERM")
   (register abort (Fn [] ()) "abort")
+
+  (register errno Int "errno")
+  (register EACCES Int "EACCES")
+  (register EEXIST Int "EEXIST")
+  (register EINVAL Int "EINVAL")
+  (register EIO Int "EIO")
+  (register EISDIR Int "EISDIR")
+  (register ELOOP Int "ELOOP")
+  (register EMFILE Int "EMFILE")
+  (register ENAMETOOLONG Int "ENAMETOOLONG")
+  (register ENOENT Int "ENOENT")
+  (register ENOMEM Int "EINVAL")
+  (register ENOSPC Int "ENOSPC")
+  (register ENOSR Int "ENOSR")
+  (register ENOTDIR Int "ENOTDIR")
+  (register ENXIO Int "ENXIO")
+  (register EOVERFLOW Int "EOVERFLOW")
+  (register EROFS Int "EROFS")
+  (register EINTR  Int "EINTR")
+
 )

test/regression.carp

@@ -34,7 +34,7 @@
                 @&Int.MAX
                 "test that the address of Int.MAX can be taken")
   (assert-equal test
-                &(Result.Error @"File “foobar” couldn’t be opened!")
+                &(Result.Error System.ENOENT)
                 &(IO.read->EOF "foobar")
                 "test that reading from an undefined file works")
   (assert-equal test

test/system.carp

@@ -0,0 +1,19 @@
+(load "Test.carp")
+
+(use-all Test IO Result)
+
+(defn open-existing-file? [filename]
+  (let [f (open-file filename "r")]
+    (match f
+           (Error _) false
+           (Success x) (do
+                         (fclose x)
+                         true))))
+
+(deftest test
+  (assert-true test
+               (error? &(open-file "asfasdfafs.txt" "r"))
+               "An error is given when the file doesn't exist")
+  (assert-true test
+               (open-existing-file? "test/system.carp")
+               "files that exist are opened properly"))