Merge pull request #1461 from Varriount/os/add-hiddenFile

Add isHidden procedure to os.nim

lib/pure/os.nim

@@ -365,6 +365,7 @@ when defined(windows):
     template getFilename(f: expr): expr = $f.cFilename
 
   proc skipFindData(f: TWIN32_FIND_DATA): bool {.inline.} =
+    # Note - takes advantage of null delimiter in the cstring
     const dot = ord('.')
     result = f.cFileName[0].int == dot and (f.cFileName[1].int == 0 or
              f.cFileName[1].int == dot and f.cFileName[2].int == 0)
@@ -1861,12 +1862,12 @@ proc expandTilde*(path: string): string =
 
 when defined(Windows):
   type
-    DeviceId = int32
+    DeviceId* = int32
-    FileId = int64
+    FileId* = int64
 else:
   type
-    DeviceId = TDev
+    DeviceId* = TDev
-    FileId = TIno
+    FileId* = TIno
 
 type
   FileInfo* = object
@@ -1909,6 +1910,7 @@ template rawToFormalFileInfo(rawInfo, formalInfo): expr =
     if (rawInfo.dwFileAttributes and FILE_ATTRIBUTE_REPARSE_POINT) != 0'i32:
       formalInfo.kind = succ(result.kind)
 
+
   else:
     template checkAndIncludeMode(rawMode, formalMode: expr) = 
       if (rawInfo.st_mode and rawMode) != 0'i32:
@@ -1995,4 +1997,26 @@ proc getFileInfo*(path: string, followSymlink = true): FileInfo =
         osError(osLastError())
     rawToFormalFileInfo(rawInfo, result)
 
+proc isHidden*(path: string): bool =
+  ## Determines whether a given path is hidden or not. Returns false if the
+  ## file doesn't exist. The given path must be accessible from the current
+  ## working directory of the program.
+  ## 
+  ## On Windows, a file is hidden if the file's 'hidden' attribute is set.
+  ## On Unix-like systems, a file is hidden if it starts with a '.' (period)
+  ## and is not *just* '.' or '..' ' ."
+  when defined(Windows):
+    wrapUnary(attributes, getFileAttributesW, path)
+    if attributes != -1'i32:
+      result = (attributes and FILE_ATTRIBUTE_HIDDEN) != 0'i32
+  else:
+    if fileExists(path):
+      let
+        fileName = extractFilename(path)
+        nameLen = len(fileName)
+      if nameLen == 2:
+        result = (fileName[0] == '.') and (fileName[1] != '.')
+      elif nameLen > 2:
+        result = (fileName[0] == '.') and (fileName[3] != '.')
+
 {.pop.}