Add exists, create and delete to directory implementation on Linux and Mac.

runtime/bin/directory_posix.cc

Index: runtime/bin/directory_posix.cc
diff --git a/runtime/bin/directory_linux.cc b/runtime/bin/directory_posix.cc
similarity index 87%
rename from runtime/bin/directory_linux.cc
rename to runtime/bin/directory_posix.cc
index 641c0cf6d433891b059f3e830ce76b142c5e10c0..96aa022378dc54018f5a33353cdfaf895af03f63 100644
--- a/runtime/bin/directory_linux.cc
+++ b/runtime/bin/directory_posix.cc
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include <dirent.h>
+#include <errno.h>
 #include <libgen.h>
 #include <string.h>
 #include <sys/param.h>
@@ -217,3 +218,42 @@ void Directory::List(const char* dir_name,
     Dart_Post(done_port, value);
   }
 }
+
+
+bool Directory::Exists(const char* dir_name, bool* result) {
+  struct stat entry_info;
+  int lstat_success = lstat(dir_name, &entry_info);
+  if (lstat_success == 0) {
+    *result = ((entry_info.st_mode & S_IFMT) == S_IFDIR);
+    return true;
+  } else {
+    if (errno == EACCES ||
+        errno == EBADF ||
+        errno == EFAULT ||
+        errno == ENOMEM ||
+        errno == EOVERFLOW) {
+      // Search permissions denied for one of the directories in the
+      // path or a low level error occured. We do not know if the
+      // directory exists.
+      return false;
+    }
+    ASSERT(errno == ELOOP ||
+           errno == ENAMETOOLONG ||
+           errno == ENOENT ||
+           errno == ENOTDIR);
+    *result = false;
+    return true;
+  }
+}
+
+
+bool Directory::Create(const char* dir_name) {
+  // Create the directory with the permissions specified by the
+  // process umask.
+  return (mkdir(dir_name, 0777) == 0);
+}
+
+
+bool Directory::Delete(const char* dir_name) {
+  return (rmdir(dir_name) == 0);
+}