Add fabricated RRO generation to libidmap2

Fabricated Runtime Resource Overlays are overlays that are generated
at runtime and are stored in the data/ partition.

The system can fabricate RROs at runtime to dynamically theme the
device. Idmaps can now be created from APK RROs and fabricated RROs.

Rather than operating on ApkAssets, libidmap2 now operates on abstract
resource "containers" that supply resource values. Target resource
containers implement methods needed to query overlayable and target
overlay information. Currently only APKs can be loaded as target
resource containers. Overlay resource containers implement methods to
supply the mapping of target resource to overlay value and other
overlay information.

The format of a fabricated RRO is as follows:
0x00 - 0x04 : fabricated overlay magic (always FRRO)
0x04 - 0x08 : file format version
0x08 - 0x0c : crc of version + proto data
0x0c - EOF  : proto fabricated overlay data

The magic is used to quickly detect if the file is a fabricated overlay.
The version is incremented whenever backwards incompatible changes are
made to the proto file format. Idmap must always be able to upgrade
fabricated overlays from previous versions to new versions, so all
previous versions must be checked into the tree.

Bug: 172471315
Test: libidmap2_tests && libandroidfw_tests
Change-Id: I4c9f29da278672e5695fb57d131a44c11a835180

1 files changed, 11 insertions, 16 deletions

diff --git a/libs/androidfw/Idmap.cpp b/libs/androidfw/Idmap.cpp
index f216f55771c2..efd1f6a25786 100644
--- a/libs/androidfw/Idmap.cpp
+++ b/libs/androidfw/Idmap.cpp
@@ -54,12 +54,6 @@ struct Idmap_header {
 };
 
 struct Idmap_data_header {
-  uint8_t target_package_id;
-  uint8_t overlay_package_id;
-
-  // Padding to ensure 4 byte alignment for target_entry_count
-  uint16_t p0;
-
   uint32_t target_entry_count;
   uint32_t target_inline_entry_count;
   uint32_t overlay_entry_count;
@@ -158,19 +152,19 @@ IdmapResMap::Result IdmapResMap::Lookup(uint32_t target_res_id) const {
     return {};
   }
 
-  // The resource ids encoded within the idmap are build-time resource ids.
-  target_res_id = (0x00FFFFFFU & target_res_id)
-      | (((uint32_t) data_header_->target_package_id) << 24U);
+  // The resource ids encoded within the idmap are build-time resource ids so do not consider the
+  // package id when determining if the resource in the target package is overlaid.
+  target_res_id &= 0x00FFFFFFU;
 
   // Check if the target resource is mapped to an overlay resource.
   auto first_entry = entries_;
   auto end_entry = entries_ + dtohl(data_header_->target_entry_count);
   auto entry = std::lower_bound(first_entry, end_entry, target_res_id,
-                                [](const Idmap_target_entry &e, const uint32_t target_id) {
-    return dtohl(e.target_id) < target_id;
+                                [](const Idmap_target_entry& e, const uint32_t target_id) {
+    return (0x00FFFFFFU & dtohl(e.target_id)) < target_id;
   });
 
-  if (entry != end_entry && dtohl(entry->target_id) == target_res_id) {
+  if (entry != end_entry && (0x00FFFFFFU & dtohl(entry->target_id)) == target_res_id) {
     uint32_t overlay_resource_id = dtohl(entry->overlay_id);
     // Lookup the resource without rewriting the overlay resource id back to the target resource id
     // being looked up.
@@ -182,12 +176,13 @@ IdmapResMap::Result IdmapResMap::Lookup(uint32_t target_res_id) const {
   auto first_inline_entry = inline_entries_;
   auto end_inline_entry = inline_entries_ + dtohl(data_header_->target_inline_entry_count);
   auto inline_entry = std::lower_bound(first_inline_entry, end_inline_entry, target_res_id,
-                                       [](const Idmap_target_entry_inline &e,
+                                       [](const Idmap_target_entry_inline& e,
                                           const uint32_t target_id) {
-    return dtohl(e.target_id) < target_id;
+    return (0x00FFFFFFU & dtohl(e.target_id)) < target_id;
   });
 
-  if (inline_entry != end_inline_entry && dtohl(inline_entry->target_id) == target_res_id) {
+  if (inline_entry != end_inline_entry &&
+      (0x00FFFFFFU & dtohl(inline_entry->target_id)) == target_res_id) {
     return Result(inline_entry->value);
   }
   return {};
@@ -235,7 +230,7 @@ std::optional<std::string_view> ReadString(const uint8_t** in_out_data_ptr, size
   }
   return std::string_view(data, *len);
 }
-}
+} // namespace
 
 LoadedIdmap::LoadedIdmap(std::string&& idmap_path,
                          const Idmap_header* header,