Add read-only environment variable access.

runtime/bin/platform_macos.cc

Index: runtime/bin/platform_macos.cc
diff --git a/runtime/bin/platform_macos.cc b/runtime/bin/platform_macos.cc
index 84cce9293ea7a5951b3d8f83bd54f40409721a9e..81455ba3d3988ae7348433d517836d4b83fb96ed 100644
--- a/runtime/bin/platform_macos.cc
+++ b/runtime/bin/platform_macos.cc
@@ -1,9 +1,10 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/platform.h"
 
+#include <crt_externs.h>
 #include <signal.h>
 #include <string.h>
 #include <unistd.h>
@@ -39,6 +40,24 @@ bool Platform::LocalHostname(char *buffer, intptr_t buffer_length) {
 }
 
 
+char** Platform::Environment(intptr_t* count) {
+  // Using environ directly is only safe as long as we do not
+  // provide access to modifying environment variables.
+  // On MacOS you have to do a bit of magic to get to the
+  // environment strings.
+  char** environ = *(_NSGetEnviron());
+  intptr_t i = 0;
+  char** tmp = environ;
+  while (*(tmp++) != NULL) i++;
+  *count = i;
+  char** result = new char*[i];
+  for (intptr_t current = 0; current < i; current++) {
+    result[current] = environ[current];
+  }
+  return result;
+}
+
+
 char* Platform::StrError(int error_code) {
   static const int kBufferSize = 1024;
   char* error = static_cast<char*>(malloc(kBufferSize));