| # AAPT2 On-Disk Formats |
| - AAPT2 Container Format (extension `.apc`) |
| - AAPT2 Static Library Format (extension `.sapk`) |
| |
| ## AAPT2 Container Format (extension `.apc`) |
| The APC format (AAPT2 Container Format) is generated by AAPT2 during the compile phase and |
| consumed by the AAPT2 link phase. It is a simple container format for storing compiled PNGs, |
| binary and protobuf XML, and intermediate protobuf resource tables. It also stores all associated |
| meta-data from the compile phase. |
| |
| ### Format |
| The file starts with a simple header. All multi-byte fields are little-endian. |
| |
| | Size (in bytes) | Field | Description | |
| |:----------------|:--------------|:-----------------------------------------------------| |
| | `4` | `magic` | The magic bytes must equal `'AAPT'` or `0x54504141`. | |
| | `4` | `version` | The version of the container format. | |
| | `4` | `entry_count` | The number of entries in this container. | |
| |
| This is followed by `entry_count` of the following data structure. It must be aligned on a 32-bit |
| boundary, so if a previous entry ends unaligned, padding must be inserted. |
| |
| | 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. 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 |
| [aapt.pb.ResourceTable](Resources.proto). |
| |
| 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` | `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`) |
| |
