libandroidfw: Add SparseEntry support for LoadedArsc
go/o-restable-sparse-entries
Test: make libandroidfw_tests
Change-Id: Ib1a7d1fc69008390eee53a1de04356dc50e05b45
diff --git a/libs/androidfw/LoadedArsc.cpp b/libs/androidfw/LoadedArsc.cpp
index c361ea2..6ee5e86 100644
--- a/libs/androidfw/LoadedArsc.cpp
+++ b/libs/androidfw/LoadedArsc.cpp
@@ -18,6 +18,7 @@
#include "androidfw/LoadedArsc.h"
+#include <algorithm>
#include <cstddef>
#include <limits>
@@ -244,31 +245,63 @@
for (uint32_t i = 0; i < type_spec_ptr->type_count; i++) {
const Type* type = &type_spec_ptr->types[i];
+ const ResTable_type* type_chunk = type->type;
if (type->configuration.match(config) &&
(best_config == nullptr || type->configuration.isBetterThan(*best_config, &config))) {
// The configuration matches and is better than the previous selection.
// Find the entry value if it exists for this configuration.
- const size_t entry_count = dtohl(type->type->entryCount);
- const size_t offsets_offset = dtohs(type->type->header.headerSize);
- if (entry_idx < entry_count) {
- // If the package hasn't been verified, do bounds checking.
- if (!Verified) {
- if (!VerifyResTableType(type->type)) {
- continue;
- }
+ const size_t entry_count = dtohl(type_chunk->entryCount);
+ const size_t offsets_offset = dtohs(type_chunk->header.headerSize);
+
+ // If the package hasn't been verified, do bounds checking.
+ if (!Verified) {
+ if (!VerifyResTableType(type_chunk)) {
+ continue;
+ }
+ }
+
+ // Check if there is the desired entry in this type.
+
+ if (type_chunk->flags & ResTable_type::FLAG_SPARSE) {
+ // This is encoded as a sparse map, so perform a binary search.
+ const ResTable_sparseTypeEntry* sparse_indices =
+ reinterpret_cast<const ResTable_sparseTypeEntry*>(
+ reinterpret_cast<const uint8_t*>(type_chunk) + offsets_offset);
+ const ResTable_sparseTypeEntry* sparse_indices_end = sparse_indices + entry_count;
+ const ResTable_sparseTypeEntry* result =
+ std::lower_bound(sparse_indices, sparse_indices_end, entry_idx,
+ [](const ResTable_sparseTypeEntry& entry, uint16_t entry_idx) {
+ return dtohs(entry.idx) < entry_idx;
+ });
+
+ if (result == sparse_indices_end || dtohs(result->idx) != entry_idx) {
+ // No entry found.
+ continue;
+ }
+
+ // Extract the offset from the entry. Each offset must be a multiple of 4 so we store it as
+ // the real offset divided by 4.
+ best_offset = dtohs(result->offset) * 4u;
+ } else {
+ if (entry_idx >= entry_count) {
+ // This entry cannot be here.
+ continue;
}
const uint32_t* entry_offsets = reinterpret_cast<const uint32_t*>(
- reinterpret_cast<const uint8_t*>(type->type) + offsets_offset);
+ reinterpret_cast<const uint8_t*>(type_chunk) + offsets_offset);
const uint32_t offset = dtohl(entry_offsets[entry_idx]);
- if (offset != ResTable_type::NO_ENTRY) {
- // There is an entry for this resource, record it.
- best_config = &type->configuration;
- best_type = type->type;
- best_offset = offset;
+ if (offset == ResTable_type::NO_ENTRY) {
+ continue;
}
+
+ // There is an entry for this resource, record it.
+ best_offset = offset;
}
+
+ best_config = &type->configuration;
+ best_type = type_chunk;
}
}
@@ -335,16 +368,29 @@
const size_t entry_count = dtohl(header->entryCount);
const size_t offsets_offset = chunk.header_size();
- // Check each entry offset.
- const uint32_t* offsets =
- reinterpret_cast<const uint32_t*>(reinterpret_cast<const uint8_t*>(header) + offsets_offset);
- for (size_t i = 0; i < entry_count; i++) {
- uint32_t offset = dtohl(offsets[i]);
- if (offset != ResTable_type::NO_ENTRY) {
+ if (header->flags & ResTable_type::FLAG_SPARSE) {
+ // This is encoded as a sparse map, so perform a binary search.
+ const ResTable_sparseTypeEntry* sparse_indices =
+ reinterpret_cast<const ResTable_sparseTypeEntry*>(reinterpret_cast<const uint8_t*>(header) +
+ offsets_offset);
+ for (size_t i = 0; i < entry_count; i++) {
+ const uint32_t offset = uint32_t{dtohs(sparse_indices[i].offset)} * 4u;
if (!VerifyResTableEntry(header, offset, i)) {
return false;
}
}
+ } else {
+ // Check each entry offset.
+ const uint32_t* offsets = reinterpret_cast<const uint32_t*>(
+ reinterpret_cast<const uint8_t*>(header) + offsets_offset);
+ for (size_t i = 0; i < entry_count; i++) {
+ uint32_t offset = dtohl(offsets[i]);
+ if (offset != ResTable_type::NO_ENTRY) {
+ if (!VerifyResTableEntry(header, offset, i)) {
+ return false;
+ }
+ }
+ }
}
return true;
}