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46 lines
2.6 KiB
Markdown
46 lines
2.6 KiB
Markdown
---
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title: "Generators"
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---
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Some templates within the ETL are designed to support a variable number of template parameters. To accommodate this, these template classes have a number of specialisations to handle each variant. The ETL sets this number to a reasonable default, but there will almost certainly be circumstances where these are too small for the project at hand.
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To this end, the ETL supplies 'generators' to enable the creation of customised variants of these template classes.
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The code generation is handled by a Python library called COG. This allows Python code to be embedded within the C++. When COG is run on the generator header, it will produce a customised version of that header.
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The naming convention used is
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The generator file: xxxx_generator.h
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The output file: xxxx.h
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The script: generate_xxxx.bat
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The script generate.bat will run all of the generate scripts.
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e.g.
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Running the COG script on the generator type_traits_generator.h will create type_traits.h
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The syntax for processing a generator file is
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python -m cogapp -d -e -o<output> -D<parameter>=<N> <generator>
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e.g.
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python -m cogapp -d -e -otype_traits.h -DIsOneOf=16 type_traits_generator.h
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The line above will create type_traits.h with the ability to handle up to 16 types in the etl::is_one_of structure.
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All of the generator files may be processed by running the script generate.bat
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There are generator scripts for each generator header.
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This can be run as a command line batch file under Windows or as a script under Linux (if set to 'executable')
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Defined generators
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Functionality Generator Output Parameters Notes
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Finite State Machine fsm_generator.h fsm.h Handlers Defines the maximum number of events that can be handled
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Message Router message_router_generator.h message_router.h Handlers Defines the maximum number of messages that can be handled
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Smallest smallest_generator.h smallest.h NTypes Defines the maximum number of types that can be declared
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Largest largest_generator.h largest.h
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NTypes Defines the maximum number of types that can be declared
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Type Traits type_traits_generator.h type_traits.h IsOneOf Defines the maximum number of types that can be declared in the class etl::is_one_of
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Type Lookup type_lookup_generator.h type_lookup.h NTypes Defines the maximum number of types that can be declared in the classes etl::type_id_lookup and etl::type_type_lookup
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Type Select type_select_generator.h type_select.h Defines the maximum number of types that can be declared in the class etl::type_select
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Variant Pool variant_pool_generator.h variant_pool.h NTypes Defines the maximum number of types that can be declared
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