Fix a bug and a documentation mistake

src/Node/Buffer.js

@@ -89,14 +89,14 @@ exports.toArray = function (buff) {
   };
 };
 
-exports.getAtOffsetImpl = function (nothing) {
-  return function (just) {
-    return function (buff) {
-      return function (offset) {
+exports.getAtOffsetImpl = function (just) {
+  return function (nothing) {
+    return function (offset) {
+      return function (buff) {
         return function() {
           var octet = buff[offset];
           return octet == null ? nothing
-                               : just(buff[i]);
+                               : just(octet);
         };
       };
     };

src/Node/Buffer.purs

@@ -28,7 +28,7 @@ import Data.Maybe (Maybe(..))
 import Node.Encoding (Encoding, encodingToNode)
 
 -- | Type synonym indicating the value should be an octet (0-255). If the value
--- | provided is outside this range it will be used as modulo 255.
+-- | provided is outside this range it will be used as modulo 256.
 type Octet = Int
 
 -- | Type synonym indicating the value refers to an offset in a buffer.

test/Main.purs

@@ -3,8 +3,9 @@ module Test.Main where
 import Prelude
 import Control.Monad.Eff (Eff)
 import Control.Monad.Eff.Console (log, CONSOLE())
+import Data.Maybe (Maybe(..))
 import Data.Traversable (traverse)
-import Node.Buffer (BUFFER, BufferValueType(..), toArray, concat', fromArray, fill, copy, readString, fromString, toString, read, write, create)
+import Node.Buffer (BUFFER, BufferValueType(..), toArray, concat', fromArray, fill, copy, readString, fromString, toString, read, write, create, getAtOffset)
 import Node.Encoding (Encoding(..))
 import Test.Assert (ASSERT, assert')
 
@@ -41,6 +42,9 @@ main = do
   log "concat'"
   testConcat'
 
+  log "getAtOffset"
+  testGetAtOffset
+
 testReadWrite :: Test
 testReadWrite = do
   buf <- create 1
@@ -120,6 +124,13 @@ testConcat' = do
 
   assertEq [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14] out
 
+testGetAtOffset :: Test
+testGetAtOffset = do
+  buf  <- fromArray [1, 2, 3, 4]
+  assertEq (Just 2) =<< getAtOffset 1 buf
+  assertEq Nothing  =<< getAtOffset 4 buf
+  assertEq Nothing  =<< getAtOffset (-1) buf
+
 assertEq :: forall a. (Eq a, Show a) => a -> a -> Test
 assertEq x y =
   if x == y