| commit | 1223654363e32d6b78389a6ef2b9f110c2aea083 | [log] [tgz] |
|---|---|---|
| author | Anton Hansson <hansson@google.com> | Tue Apr 12 20:34:06 2022 +0100 |
| committer | Anton Hansson <hansson@google.com> | Tue Apr 12 20:34:06 2022 +0100 |
| tree | c3fb98319129fd03e2114022a0dffa42066f2396 | |
| parent | 9f6dd556bc0572952208f3716e33f3b629e024a1 [diff] |
Update README for creating a new extension - Add a missing step (adding the binary pb to apexes) - Make it refer to "extension" instead of "extension version" - Make it a bit more generic. We could conceptually add extensions other than ones that align with the SDK level. Test: No Change-Id: I6bf4ffd37553282ba6f7978446e27758b916935f
SdkExtensions module is responsible for:
The module is packaged in an apex, com.android.sdkext, and has several components:
bin/derive_classpath: a native binary that runs early in the device boot process. It reads individual classpath configs files from the system and other modules, merges them, and defines the definition of *CLASSPATH environ variables.bin/derive_sdk: native binary that runs early in the device boot process and reads metadata of other modules, to set system properties relating to the extension SDK (for instance build.version.extensions.r).javalib/framework-sdkextension.jar: this is a jar on the bootclasspath that exposes APIs to applications to query the extension SDK level.derive_sdk is a program that reads metadata stored in other apex modules, in the form of binary protobuf files in subpath etc/sdkinfo.pb inside each apex. The structure of this protobuf can be seen here. The exact steps for converting a set of metadata files to actual extension versions is likely to change over time, and should not be depended upon.
The module exposes a java class SdkExtensions in the package android.os.ext. The method getExtensionVersion(int) can be used to read the version of a particular sdk extension, e.g. getExtensionVersion(Build.VERSION_CODES.R).
derive_classpath service reads and merges individual config files in the /system/etc/classpaths/ and /apex/*/etc/classpaths. Each config stores protobuf message from classpaths.proto in a proto binary format. Exact merging algorithm that determines the order of the classpath entries is described in derive_classpath.cpp and may change over time.
An extension is a way to group a set of modules so that they are versioned together. We currently define a new extension for every Android SDK level that introduces new modules. Every module shipped in previous versions are also part of the new extension. For example, all the R modules are part of both the R extensions and the S extensions.
The steps to define a new extension are:
derive_sdk.cpp by:GetSdkLevel with the new enum setderive_sdk_test.cpp verifying the new extensions workSdkExtensions.getExtensionVersion API support the new extensions.