Fix computation of 'entry_length' in AAPT2 container format
When the protobuf header (or data payload) size are a multiple of 4,
"entry_length" (called "aligned size" in the code) would have counted bytes that
are never actually written.
Bug: 139418052
Change-Id: Ia688a82a67f3807f7feb0be03670bf2827b1d6a1
(cherry picked from commit b99e50922bf8a5eb9f034c1d232646fda122e83c)
diff --git a/tools/aapt2/format/Container.cpp b/tools/aapt2/format/Container.cpp
index f189048..9cef7b3 100644
--- a/tools/aapt2/format/Container.cpp
+++ b/tools/aapt2/format/Container.cpp
@@ -30,6 +30,7 @@
constexpr const static uint32_t kContainerFormatMagic = 0x54504141u;
constexpr const static uint32_t kContainerFormatVersion = 1u;
+constexpr const static size_t kPaddingAlignment = 4u;
ContainerWriter::ContainerWriter(ZeroCopyOutputStream* out, size_t entry_count)
: out_(out), total_entry_count_(entry_count), current_entry_count_(0u) {
@@ -49,11 +50,17 @@
}
}
-inline static void WritePadding(int padding, CodedOutputStream* out) {
- if (padding < 4) {
- const uint32_t zero = 0u;
- out->WriteRaw(&zero, padding);
- }
+inline static size_t CalculatePaddingForAlignment(size_t size) {
+ size_t overage = size % kPaddingAlignment;
+ return overage == 0 ? 0 : kPaddingAlignment - overage;
+}
+
+inline static void WritePadding(size_t padding, CodedOutputStream* out) {
+ CHECK(padding < kPaddingAlignment);
+ const uint32_t zero = 0u;
+ static_assert(sizeof(zero) >= kPaddingAlignment, "Not enough source bytes for padding");
+
+ out->WriteRaw(&zero, padding);
}
bool ContainerWriter::AddResTableEntry(const pb::ResourceTable& table) {
@@ -70,7 +77,7 @@
// Write the aligned size.
const ::google::protobuf::uint64 size = table.ByteSize();
- const int padding = 4 - (size % 4);
+ const int padding = CalculatePaddingForAlignment(size);
coded_out.WriteLittleEndian64(size);
// Write the table.
@@ -103,9 +110,9 @@
// Write the aligned size.
const ::google::protobuf::uint32 header_size = file.ByteSize();
- const int header_padding = 4 - (header_size % 4);
+ const int header_padding = CalculatePaddingForAlignment(header_size);
const ::google::protobuf::uint64 data_size = in->TotalSize();
- const int data_padding = 4 - (data_size % 4);
+ const int data_padding = CalculatePaddingForAlignment(data_size);
coded_out.WriteLittleEndian64(kResFileEntryHeaderSize + header_size + header_padding + data_size +
data_padding);
diff --git a/tools/aapt2/formats.md b/tools/aapt2/formats.md
index bb31a00..25a0e79 100644
--- a/tools/aapt2/formats.md
+++ b/tools/aapt2/formats.md
@@ -23,7 +23,7 @@
| Size (in bytes) | Field | Description |
|:----------------|:---------------|:----------------------------------------------------------------------------------------------------------|
| `4` | `entry_type` | The type of the entry. This can be one of two types: `RES_TABLE (0x00000000)` or `RES_FILE (0x00000001)`. |
-| `8` | `entry_length` | The length of the data that follows. |
+| `8` | `entry_length` | The length of the data that follows. Do not use if `entry_type` is `RES_FILE`; this value may be wrong. |
| `entry_length` | `data` | The payload. The contents of this varies based on the `entry_type`. |
If the `entry_type` is equal to `RES_TABLE (0x00000000)`, the `data` field contains a serialized
@@ -32,13 +32,14 @@
If the `entry_type` is equal to `RES_FILE (0x00000001)`, the `data` field contains the following:
-| Size (in bytes) | Field | Description |
-|:----------------|:---------------|:----------------------------------------------------------------------------------------------------------|
-| `4` | `header_size` | The size of the `header` field. |
-| `8` | `data_size` | The size of the `data` field. |
-| `header_size` | `header` | The serialized Protobuf message [aapt.pb.internal.CompiledFile](ResourcesInternal.proto). |
-| `x` | `padding` | Up to 4 bytes of zeros, if padding is necessary to align the `data` field on a 32-bit boundary. |
-| `data_size` | `data` | The payload, which is determined by the `type` field in the `aapt.pb.internal.CompiledFile`. This can be a PNG file, binary XML, or [aapt.pb.XmlNode](Resources.proto). |
+| Size (in bytes) | Field | Description |
+|:----------------|:-----------------|:----------------------------------------------------------------------------------------------------------|
+| `4` | `header_size` | The size of the `header` field. |
+| `8` | `data_size` | The size of the `data` field. |
+| `header_size` | `header` | The serialized Protobuf message [aapt.pb.internal.CompiledFile](ResourcesInternal.proto). |
+| `x` | `header_padding` | Up to 3 bytes of zeros, if padding is necessary to align the `data` field on a 32-bit boundary. |
+| `data_size` | `data` | The payload, which is determined by the `type` field in the `aapt.pb.internal.CompiledFile`. This can be a PNG file, binary XML, or [aapt.pb.XmlNode](Resources.proto). |
+| `y` | `data_padding` | Up to 3 bytes of zeros, if `data_size` is not a multiple of 4. |
## AAPT2 Static Library Format (extension `.sapk`)
