diff --git a/include/utils/AssetManager.h b/include/utils/AssetManager.h
index 9e2bf37..a8c7ddb 100644
--- a/include/utils/AssetManager.h
+++ b/include/utils/AssetManager.h
@@ -222,6 +222,7 @@
     {
         String8 path;
         FileType type;
+        String8 idmap;
     };
 
     Asset* openInPathLocked(const char* fileName, AccessMode mode,
@@ -262,6 +263,16 @@
     void setLocaleLocked(const char* locale);
     void updateResourceParamsLocked() const;
 
+    bool createIdmapFileLocked(const String8& originalPath, const String8& overlayPath,
+                               const String8& idmapPath);
+
+    bool isIdmapStaleLocked(const String8& originalPath, const String8& overlayPath,
+                            const String8& idmapPath);
+
+    Asset* openIdmapLocked(const struct asset_path& ap) const;
+
+    bool getZipEntryCrcLocked(const String8& zipPath, const char* entryFilename, uint32_t* pCrc);
+
     class SharedZip : public RefBase {
     public:
         static sp<SharedZip> get(const String8& path);
diff --git a/include/utils/ResourceTypes.h b/include/utils/ResourceTypes.h
index ab7b973..10baa11 100644
--- a/include/utils/ResourceTypes.h
+++ b/include/utils/ResourceTypes.h
@@ -1735,9 +1735,9 @@
     ~ResTable();
 
     status_t add(const void* data, size_t size, void* cookie,
-                 bool copyData=false);
+                 bool copyData=false, const void* idmap = NULL);
     status_t add(Asset* asset, void* cookie,
-                 bool copyData=false);
+                 bool copyData=false, const void* idmap = NULL);
     status_t add(ResTable* src);
 
     status_t getError() const;
@@ -1981,6 +1981,24 @@
 
     void getLocales(Vector<String8>* locales) const;
 
+    // Generate an idmap.
+    //
+    // Return value: on success: NO_ERROR; caller is responsible for free-ing
+    // outData (using free(3)). On failure, any status_t value other than
+    // NO_ERROR; the caller should not free outData.
+    status_t createIdmap(const ResTable& overlay, uint32_t originalCrc, uint32_t overlayCrc,
+                         void** outData, size_t* outSize) const;
+
+    enum {
+        IDMAP_HEADER_SIZE_BYTES = 3 * sizeof(uint32_t),
+    };
+    // Retrieve idmap meta-data.
+    //
+    // This function only requires the idmap header (the first
+    // IDMAP_HEADER_SIZE_BYTES) bytes of an idmap file.
+    static bool getIdmapInfo(const void* idmap, size_t size,
+                             uint32_t* pOriginalCrc, uint32_t* pOverlayCrc);
+
 #ifndef HAVE_ANDROID_OS
     void print(bool inclValues) const;
     static String8 normalizeForOutput(const char* input);
@@ -1994,7 +2012,7 @@
     struct bag_set;
 
     status_t add(const void* data, size_t size, void* cookie,
-                 Asset* asset, bool copyData);
+                 Asset* asset, bool copyData, const Asset* idmap);
 
     ssize_t getResourcePackageIndex(uint32_t resID) const;
     ssize_t getEntry(
@@ -2003,7 +2021,7 @@
         const ResTable_type** outType, const ResTable_entry** outEntry,
         const Type** outTypeClass) const;
     status_t parsePackage(
-        const ResTable_package* const pkg, const Header* const header);
+        const ResTable_package* const pkg, const Header* const header, uint32_t idmap_id);
 
     void print_value(const Package* pkg, const Res_value& value) const;