45 lines
3.2 KiB
Markdown
45 lines
3.2 KiB
Markdown
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# AAPT2 On-Disk Formats
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- AAPT2 Container Format (extension `.apc`)
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- AAPT2 Static Library Format (extension `.sapk`)
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## AAPT2 Container Format (extension `.apc`)
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The APC format (AAPT2 Container Format) is generated by AAPT2 during the compile phase and
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consumed by the AAPT2 link phase. It is a simple container format for storing compiled PNGs,
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binary and protobuf XML, and intermediate protobuf resource tables. It also stores all associated
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meta-data from the compile phase.
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### Format
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The file starts with a simple header. All multi-byte fields are little-endian.
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| Size (in bytes) | Field | Description |
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|:----------------|:--------------|:-----------------------------------------------------|
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| `4` | `magic` | The magic bytes must equal `'AAPT'` or `0x54504141`. |
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| `4` | `version` | The version of the container format. |
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| `4` | `entry_count` | The number of entries in this container. |
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This is followed by `entry_count` of the following data structure. It must be aligned on a 32-bit
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boundary, so if a previous entry ends unaligned, padding must be inserted.
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| Size (in bytes) | Field | Description |
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|:----------------|:---------------|:----------------------------------------------------------------------------------------------------------|
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| `4` | `entry_type` | The type of the entry. This can be one of two types: `RES_TABLE (0x00000000)` or `RES_FILE (0x00000001)`. |
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| `8` | `entry_length` | The length of the data that follows. |
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| `entry_length` | `data` | The payload. The contents of this varies based on the `entry_type`. |
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If the `entry_type` is equal to `RES_TABLE (0x00000000)`, the `data` field contains a serialized
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[aapt.pb.ResourceTable](Resources.proto).
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If the `entry_type` is equal to `RES_FILE (0x00000001)`, the `data` field contains the following:
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| Size (in bytes) | Field | Description |
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|:----------------|:---------------|:----------------------------------------------------------------------------------------------------------|
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| `4` | `header_size` | The size of the `header` field. |
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| `8` | `data_size` | The size of the `data` field. |
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| `header_size` | `header` | The serialized Protobuf message [aapt.pb.internal.CompiledFile](ResourcesInternal.proto). |
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| `x` | `padding` | Up to 4 bytes of zeros, if padding is necessary to align the `data` field on a 32-bit boundary. |
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| `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). |
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## AAPT2 Static Library Format (extension `.sapk`)
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