86 lines
2.7 KiB
C
86 lines
2.7 KiB
C
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#ifndef NEOGPS_CFG
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#define NEOGPS_CFG
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/**
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* Enable/disable packed data structures.
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*
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* Enabling packed data structures will use two less-portable language
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* features of GCC to reduce RAM requirements. Although it was expected to slightly increase execution time and code size, the reverse is true on 8-bit AVRs: the code is smaller and faster with packing enabled.
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*
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* Disabling packed data structures will be very portable to other
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* platforms. NeoGPS configurations will use slightly more RAM, and on
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* 8-bit AVRs, the speed is slightly slower, and the code is slightly
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* larger. There may be no choice but to disable packing on processors
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* that do not support packed structures.
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*
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* There may also be compiler-specific switches that affect packing and the
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* code which accesses packed members. YMMV.
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**/
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#ifdef __AVR__
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#define NEOGPS_PACKED_DATA
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#endif
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//------------------------------------------------------------------------
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// Based on the above define, choose which set of packing macros should
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// be used in the rest of the NeoGPS package. Do not change these defines.
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#ifdef NEOGPS_PACKED_DATA
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// This is for specifying the number of bits to be used for a
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// member of a struct. Booleans are typically one bit.
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#define NEOGPS_BF(b) :b
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// This is for requesting the compiler to pack the struct or class members
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// "as closely as possible". This is a compiler-dependent interpretation.
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#define NEOGPS_PACKED __attribute__((packed))
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#else
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// Let the compiler do whatever it wants.
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#define NEOGPS_PACKED
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#define NEOGPS_BF(b)
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#endif
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/*
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* Accommodate C++ compiler and IDE changes.
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*
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* Declaring constants as class data instead of instance data helps avoid
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* collisions with #define names, and allows the compiler to perform more
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* checks on their usage.
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*
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* Until C++ 10 and IDE 1.6.8, initialized class data constants
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* were declared like this:
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*
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* static const <valued types> = <constant-value>;
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*
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* Now, non-simple types (e.g., float) must be declared as
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*
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* static constexpr <nonsimple-types> = <expression-treated-as-const>;
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*
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* The good news is that this allows the compiler to optimize out an
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* expression that is "promised" to be "evaluatable" as a constant.
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* The bad news is that it introduces a new language keyword, and the old
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* code raises an error.
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*
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* TODO: Evaluate the requirement for the "static" keyword.
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* TODO: Evaluate using a C++ version preprocessor symbol for the #if.
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*
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* The CONST_CLASS_DATA define will expand to the appropriate keywords.
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*
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*/
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#if ARDUINO < 10606
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#define CONST_CLASS_DATA static const
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#else
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#define CONST_CLASS_DATA static constexpr
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#endif
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#endif
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