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126 lines
3.8 KiB
Markdown
126 lines
3.8 KiB
Markdown
Application framework
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=======
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## Directory structure
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This folder "app-native-shared" is for the source files shared by both WASM APP and native runtime
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- The c files in this directory are compiled into both the WASM APP and runtime.
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- The header files for distributing to SDK are placed in the "bi-inc" folder.
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This folder "template" contains a pre-defined directory structure for a framework component. The developers can copy the template folder to create new components to the application framework.
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Every other subfolder is framework component. Each component contains two library parts: **app and native**.
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- The "base" component provide timer API and inter-app communication support. It must be enabled if other components are selected.
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- Under the "app" folder of a component, the subfolder "wa_inc" holds all header files that should be included by the WASM applications
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## Application framework basic model
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The app framework is built on top of two fundamental operations:
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- [Native calls into WASM function](../../doc/embed_wamr.md)
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- [WASM app calls into native API](../../doc/export_native_api.md)
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Asynchronized programming model is supported for WASM applications
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- Every WASM app has its own sandbox and thread
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- Queue and messaging
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<img src="../../doc/pics/app_framework.PNG" style="zoom:67%;" />
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## Customized building of app framework
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A component can be compilation configurable to the runtime. The wamr SDK tool "build_sdk.sh" supports menu config to select app components for building a customized runtime.
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A number of CMAKE variables are defined to control build of framework and components. You can create a cmake file for defining these variables and include it in the CMakeList.txt for your software, or pass it in "-x" argument when run the [build_sdk.sh](../../wamr-sdk/build_sdk.sh) for building the runtime SDK.
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```cmake
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set (WAMR_BUILD_APP_FRAMEWORK 1)
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set (WAMR_BUILD_APP_LIST WAMR_APP_BUILD_BASE)
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```
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Variables:
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- **WAMR_BUILD_APP_FRAMEWORK**: enable the application framework
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- **WAMR_BUILD_APP_LIST**: the selected components to be built into the final runtime
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The configuration file can be generated through the wamr-sdk menu config:
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```bash
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cd wamr-sdk
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./build_sdk -n [profile] -i
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```
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## Create new components
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Generally you should follow following steps to create a new component:
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- Copy the “template” for creating a new folder
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- Implement the app part
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- If your component exports native function to WASM, ensure your created a header file under app for declaring the function prototype.
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- If you component provides header files for the WASM applications to include, ensure it is placed under subfolder "wa_inc".
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- Implement the native part
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- If your native function is exported to WASM, you need to create an inl file for the registration. It can be any file name, assuming the file name is "my_component.inl" here:
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```c
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//use right signature for your functions
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EXPORT_WASM_API_WITH_SIG(wasm_my_component_api_1, "(i*~)i"),
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EXPORT_WASM_API_WITH_SIG(wasm_my_component_api_2, "(i)i"),
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```
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- Ensure "wasm_lib.cmake" is provided as it will be included by the WAMR SDK building script
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- Add a definition in "wasm_lib.cmake" for your component, e.g.
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```cmake
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add_definitions (-DAPP_FRAMEWORK_MY_COMPONENT)
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```
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- Modify the file [app_ext_lib_export.c](./app_ext_lib_export.c) to register native APIs exported for the new introduced component. Skip it if not exporting native functions.
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```
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#include "lib_export.h"
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...
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#ifdef APP_FRAMEWORK_MY_COMPONENT // this definition is created in wasm_lib.cmake
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#include "my_component_native_api.h"
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#endif
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static NativeSymbol extended_native_symbol_defs[] = {
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...
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#ifdef APP_FRAMEWORK_MY_COMPONENT
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#include "my_component.inl"
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#endif
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};
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```
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## Sensor component working flow
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