androidfw: Add support for compact resource entries
Bug: 237583012
Given the large number of simple resources such as strings in
Android resources, their ResTable_entry and Res_value can be
encoded together in a compact way. This allows a significant
saving in both storage and memory footprint.
The basic observations for simple resources are:
* ResTable_entry.size will always be sizeof(ResTable_entry)
unless it's a complex entry
* ResTable_entry.key is unlikely to exceed 16-bit
* ResTable_entry.flags only uses 3 bits for now
* Res_value.size will always be sizeof(Res_value)
Given the above, we could well encode the information into
a compact/compatible structure.
struct compact {
uint16_t key;
uint16_t flags;
uint32_t data;
};
The layout of this structure will allow maximum backward
compatibility. e.g. the flags will be at the same offset,
and a
`dtohs((ResTable_entry *)entry->flags) & FLAG_COMPACT`
would tell if this entry is a compact one or not. For a
compact entry:
struct compact *entry;
entry_size == sizeof(*entry)
entry_key == static_cast<uint32_t>(dtohs(entry->key))
entry_flags == dtohs(entry->flags) & 0xff // low 8-bit
data_type == dtohs(entry->flags) >> 8 // high 8-bit
data_size == sizeof(Res_value)
data_value == dtohl(entry->data)
To allow minimum code change and backward compatibility,
we change 'struct ResTable_entry' to 'union ResTable_entry',
with an anonymous structure inside that's fully backward
compatible. Thus, any existing reference such as:
ResTable_entry *entry = ...
if (dtohs(entry->flags) & ResTable_entry::FLAG_COMPLEX) ...
would still work.
However, special care needs to be taken after an entry is
obtained, and when value needs to be extracted.
A compact entry will not encode a complex value, and hence
complex entries/values are handled the same way.
Change-Id: I15d97a4f5e85fab28c075496f7f0cf6b1fcd73e3
diff --git a/tools/aapt2/Debug.cpp b/tools/aapt2/Debug.cpp
index f9e52b4..df87889 100644
--- a/tools/aapt2/Debug.cpp
+++ b/tools/aapt2/Debug.cpp
@@ -687,32 +687,32 @@
continue;
}
- printer_->Print((entry->flags & ResTable_entry::FLAG_COMPLEX) ? "[ResTable_map_entry]"
- : "[ResTable_entry]");
+ if (entry->is_complex()) {
+ printer_->Print("[ResTable_map_entry]");
+ } else if (entry->is_compact()) {
+ printer_->Print("[ResTable_entry_compact]");
+ } else {
+ printer_->Print("[ResTable_entry]");
+ }
+
printer_->Print(StringPrintf(" id: 0x%04x", it.index()));
printer_->Print(StringPrintf(
- " name: %s",
- android::util::GetString(key_pool_, android::util::DeviceToHost32(entry->key.index))
- .c_str()));
- printer_->Print(
- StringPrintf(" keyIndex: %u", android::util::DeviceToHost32(entry->key.index)));
- printer_->Print(StringPrintf(" size: %u", android::util::DeviceToHost32(entry->size)));
- printer_->Print(StringPrintf(" flags: 0x%04x", android::util::DeviceToHost32(entry->flags)));
+ " name: %s", android::util::GetString(key_pool_, entry->key()).c_str()));
+ printer_->Print(StringPrintf(" keyIndex: %u", entry->key()));
+ printer_->Print(StringPrintf(" size: %zu", entry->size()));
+ printer_->Print(StringPrintf(" flags: 0x%04x", entry->flags()));
printer_->Indent();
- if (entry->flags & ResTable_entry::FLAG_COMPLEX) {
- auto map_entry = (const ResTable_map_entry*)entry;
- printer_->Print(
- StringPrintf(" count: 0x%04x", android::util::DeviceToHost32(map_entry->count)));
+ if (auto map_entry = entry->map_entry()) {
+ uint32_t map_entry_count = android::util::DeviceToHost32(map_entry->count);
+ printer_->Print(StringPrintf(" count: 0x%04x", map_entry_count));
printer_->Print(StringPrintf(" parent: 0x%08x\n",
android::util::DeviceToHost32(map_entry->parent.ident)));
// Print the name and value mappings
- auto maps = (const ResTable_map*)((const uint8_t*)entry +
- android::util::DeviceToHost32(entry->size));
- for (size_t i = 0, count = android::util::DeviceToHost32(map_entry->count); i < count;
- i++) {
+ auto maps = (const ResTable_map*)((const uint8_t*)entry + entry->size());
+ for (size_t i = 0; i < map_entry_count; i++) {
PrintResValue(&(maps[i].value), config, type);
printer_->Print(StringPrintf(
@@ -725,9 +725,8 @@
printer_->Print("\n");
// Print the value of the entry
- auto value =
- (const Res_value*)((const uint8_t*)entry + android::util::DeviceToHost32(entry->size));
- PrintResValue(value, config, type);
+ Res_value value = entry->value();
+ PrintResValue(&value, config, type);
}
printer_->Undent();