diff -r 000000000000 -r 6474c204b198 xpcom/threads/nsEnvironment.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/threads/nsEnvironment.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,160 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsEnvironment.h"
+#include "prenv.h"
+#include "prprf.h"
+#include "nsBaseHashtable.h"
+#include "nsHashKeys.h"
+#include "nsPromiseFlatString.h"
+#include "nsDependentString.h"
+#include "nsNativeCharsetUtils.h"
+
+using namespace mozilla;
+
+NS_IMPL_ISUPPORTS(nsEnvironment, nsIEnvironment)
+
+nsresult
+nsEnvironment::Create(nsISupports *aOuter, REFNSIID aIID,
+                      void **aResult)
+{
+    nsresult rv;
+    *aResult = nullptr;
+
+    if (aOuter != nullptr) {
+        return NS_ERROR_NO_AGGREGATION;
+    }
+
+    nsEnvironment* obj = new nsEnvironment();
+    if (!obj) {
+        return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    rv = obj->QueryInterface(aIID, aResult);
+    if (NS_FAILED(rv)) {
+      delete obj;
+    }
+    return rv;
+}
+
+nsEnvironment::~nsEnvironment()
+{
+}
+
+NS_IMETHODIMP
+nsEnvironment::Exists(const nsAString& aName, bool *aOutValue)
+{
+    nsAutoCString nativeName;
+    nsresult rv = NS_CopyUnicodeToNative(aName, nativeName);
+    if (NS_WARN_IF(NS_FAILED(rv)))
+        return rv;
+
+    nsAutoCString nativeVal;
+#if defined(XP_UNIX)
+    /* For Unix/Linux platforms we follow the Unix definition:
+     * An environment variable exists when |getenv()| returns a non-nullptr
+     * value. An environment variable does not exist when |getenv()| returns
+     * nullptr.
+     */
+    const char *value = PR_GetEnv(nativeName.get());
+    *aOutValue = value && *value;
+#else
+    /* For non-Unix/Linux platforms we have to fall back to a 
+     * "portable" definition (which is incorrect for Unix/Linux!!!!)
+     * which simply checks whether the string returned by |Get()| is empty
+     * or not.
+     */
+    nsAutoString value;
+    Get(aName, value);
+    *aOutValue = !value.IsEmpty();
+#endif /* XP_UNIX */
+
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEnvironment::Get(const nsAString& aName, nsAString& aOutValue)
+{
+    nsAutoCString nativeName;
+    nsresult rv = NS_CopyUnicodeToNative(aName, nativeName);
+    if (NS_WARN_IF(NS_FAILED(rv)))
+        return rv;
+
+    nsAutoCString nativeVal;
+    const char *value = PR_GetEnv(nativeName.get());
+    if (value && *value) {
+        rv = NS_CopyNativeToUnicode(nsDependentCString(value), aOutValue);
+    } else {
+        aOutValue.Truncate();
+        rv = NS_OK;
+    }
+
+    return rv;
+}
+
+/* Environment strings must have static duration; We're gonna leak all of this
+ * at shutdown: this is by design, caused how Unix/Linux implement environment
+ * vars. 
+ */
+
+typedef nsBaseHashtableET<nsCharPtrHashKey,char*> EnvEntryType;
+typedef nsTHashtable<EnvEntryType> EnvHashType;
+
+static EnvHashType *gEnvHash = nullptr;
+
+static bool
+EnsureEnvHash()
+{
+    if (gEnvHash)
+        return true;
+
+    gEnvHash = new EnvHashType;
+    if (!gEnvHash)
+        return false;
+
+    return true;
+}
+
+NS_IMETHODIMP
+nsEnvironment::Set(const nsAString& aName, const nsAString& aValue)
+{
+    nsAutoCString nativeName;
+    nsAutoCString nativeVal;
+
+    nsresult rv = NS_CopyUnicodeToNative(aName, nativeName);
+    if (NS_WARN_IF(NS_FAILED(rv)))
+        return rv;
+
+    rv = NS_CopyUnicodeToNative(aValue, nativeVal);
+    if (NS_WARN_IF(NS_FAILED(rv)))
+        return rv;
+
+    MutexAutoLock lock(mLock);
+
+    if (!EnsureEnvHash()){
+        return NS_ERROR_UNEXPECTED;
+    }
+
+    EnvEntryType* entry = gEnvHash->PutEntry(nativeName.get());
+    if (!entry) {
+        return NS_ERROR_OUT_OF_MEMORY;
+    }
+    
+    char* newData = PR_smprintf("%s=%s",
+                                nativeName.get(),
+                                nativeVal.get());
+    if (!newData) {
+        return NS_ERROR_OUT_OF_MEMORY;
+    } 
+    
+    PR_SetEnv(newData);
+    if (entry->mData) {
+        PR_smprintf_free(entry->mData);
+    }
+    entry->mData = newData;
+    return NS_OK;
+}
+
+