--- a/intl/hyphenation/src/Makefile.in
+++ b/intl/hyphenation/src/Makefile.in
@@ -46,11 +46,12 @@ MODULE           = hyphenation
 LIBRARY_NAME     = hyphenation_s
 LIBXUL_LIBRARY   = 1
 
 CSRCS            = hyphen.c \
                    $(NULL)
 
 CPPSRCS          = nsHyphenator.cpp \
                    nsHyphenationManager.cpp \
+                   hnjstdio.cpp \
                    $(NULL)
 
 include $(topsrcdir)/config/rules.mk

--- a/intl/hyphenation/src/hnjalloc.h
+++ b/intl/hyphenation/src/hnjalloc.h
@@ -43,8 +43,41 @@
  */
 
 #include "mozilla/mozalloc.h"
 
 #define hnj_malloc(size)      moz_xmalloc(size)
 #define hnj_realloc(p, size)  moz_xrealloc(p, size)
 #define hnj_free(p)           moz_free(p)
 
+/*
+ * To enable us to load hyphenation dictionaries from arbitrary resource URIs,
+ * not just through file paths using stdio, we override the (few) stdio APIs
+ * that hyphen.c uses and provide our own reimplementation that calls Gecko
+ * i/o methods.
+ */
+
+#include <stdio.h> /* ensure stdio.h is loaded before our macros */
+
+#undef FILE
+#define FILE hnjFile
+
+#define fopen(path,mode)      hnjFopen(path,mode)
+#define fclose(file)          hnjFclose(file)
+#define fgets(buf,count,file) hnjFgets(buf,count,file)
+
+typedef struct hnjFile_ hnjFile;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+hnjFile* hnjFopen(const char* aURISpec, const char* aMode);
+
+int hnjFclose(hnjFile* f);
+
+char* hnjFgets(char* s, int n, hnjFile* f);
+
+#ifdef __cplusplus
+}
+#endif
+
+

new file mode 100644
--- /dev/null
+++ b/intl/hyphenation/src/hnjstdio.cpp
@@ -0,0 +1,137 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Mozilla Hyphenation Service.
+ *
+ * The Initial Developer of the Original Code is
+ * Mozilla Foundation.
+ * Portions created by the Initial Developer are Copyright (C) 2011
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Jonathan Kew <jfkthame@gmail.com>
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+// This file provides substitutes for the basic stdio routines used by hyphen.c
+// to read its dictionary files. We #define the stdio names to these versions
+// in hnjalloc.h, so that we can use nsIURI and nsIInputStream to specify and
+// access the dictionary resources.
+
+#include "hnjalloc.h"
+#include "nsNetUtil.h"
+
+#define BUFSIZE 1024
+
+struct hnjFile_ {
+    nsCOMPtr<nsIInputStream> mStream;
+    char                     mBuffer[BUFSIZE];
+    PRUint32                 mCurPos;
+    PRUint32                 mLimit;
+};
+
+// replacement for fopen()
+// (not a full substitute: only supports read access)
+hnjFile*
+hnjFopen(const char* aURISpec, const char* aMode)
+{
+    // this override only needs to support "r"
+    NS_ASSERTION(!strcmp(aMode, "r"), "unsupported fopen() mode in hnjFopen");
+
+    nsCOMPtr<nsIURI> uri;
+    nsresult rv = NS_NewURI(getter_AddRefs(uri), aURISpec);
+    if (NS_FAILED(rv)) {
+        return nsnull;
+    }
+
+    nsCOMPtr<nsIInputStream> instream;
+    rv = NS_OpenURI(getter_AddRefs(instream), uri);
+    if (NS_FAILED(rv)) {
+        return nsnull;
+    }
+
+    hnjFile *f = new hnjFile;
+    f->mStream = instream;
+    f->mCurPos = 0;
+    f->mLimit = 0;
+
+    return f;
+}
+
+// replacement for fclose()
+int
+hnjFclose(hnjFile* f)
+{
+    NS_ASSERTION(f && f->mStream, "bad argument to hnjFclose");
+
+    int result = 0;
+    nsresult rv = f->mStream->Close();
+    if (NS_FAILED(rv)) {
+        result = EOF;
+    }
+    f->mStream = nsnull;
+
+    delete f;
+    return result;
+}
+
+// replacement for fgets()
+// (not a full reimplementation, but sufficient for libhyphen's needs)
+char*
+hnjFgets(char* s, int n, hnjFile* f)
+{
+    NS_ASSERTION(s && f, "bad argument to hnjFgets");
+
+    int i = 0;
+    while (i < n - 1) {
+        if (f->mCurPos < f->mLimit) {
+            char c = f->mBuffer[f->mCurPos++];
+            s[i++] = c;
+            if (c == '\n' || c == '\r') {
+                break;
+            }
+            continue;
+        }
+
+        f->mCurPos = 0;
+
+        nsresult rv = f->mStream->Read(f->mBuffer, BUFSIZE, &f->mLimit);
+        if (NS_FAILED(rv)) {
+            f->mLimit = 0;
+            return nsnull;
+        }
+
+        if (f->mLimit == 0) {
+            break;
+        }
+    }
+
+    if (i == 0) {
+        return nsnull; // end of file
+    }
+
+    s[i] = '\0'; // null-terminate the returned string
+    return s;
+}

--- a/intl/hyphenation/src/nsHyphenator.cpp
+++ b/intl/hyphenation/src/nsHyphenator.cpp
@@ -35,33 +35,35 @@
  *
  * ***** END LICENSE BLOCK ***** */
 
 #include "nsHyphenator.h"
 #include "nsIFile.h"
 #include "nsUTF8Utils.h"
 #include "nsIUGenCategory.h"
 #include "nsUnicharUtilCIID.h"
+#include "nsNetUtil.h"
 
 #include "hyphen.h"
 
 nsHyphenator::nsHyphenator(nsIFile *aFile)
   : mDict(nsnull)
 {
-  nsCString path;
-  aFile->GetNativePath(path);
-  mDict = hnj_hyphen_load(path.get());
+  nsCString urlSpec;
+  nsresult rv = NS_GetURLSpecFromFile(aFile, urlSpec);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+  mDict = hnj_hyphen_load(urlSpec.get());
 #ifdef DEBUG
   if (mDict) {
-    printf("loaded hyphenation patterns from %s\n", path.get());
+    printf("loaded hyphenation patterns from %s\n", urlSpec.get());
   }
 #endif
-  nsresult rv;
-  mCategories =
-    do_GetService(NS_UNICHARCATEGORY_CONTRACTID, &rv);
+  mCategories = do_GetService(NS_UNICHARCATEGORY_CONTRACTID, &rv);
   NS_ASSERTION(NS_SUCCEEDED(rv), "failed to get category service");
 }
 
 nsHyphenator::~nsHyphenator()
 {
   if (mDict != nsnull) {
     hnj_hyphen_free((HyphenDict*)mDict);
     mDict = nsnull;