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26 lines
1.0 KiB
26 lines
1.0 KiB
Nanopb example "using_double_on_avr"
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Some processors/compilers, such as AVR-GCC, do not support the double
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datatype. Instead, they have sizeof(double) == 4. Because protocol
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binary format uses the double encoding directly, this causes trouble
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if the protocol in .proto requires double fields.
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This directory contains a solution to this problem. It uses uint64_t
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to store the raw wire values, because its size is correct on all
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platforms. The file double_conversion.c provides functions that
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convert these values to/from floats, without relying on compiler
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support.
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To use this method, you need to make some modifications to your code:
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1) Change all 'double' fields into 'fixed64' in the .proto.
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2) Whenever writing to a 'double' field, use float_to_double().
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3) Whenever reading a 'double' field, use double_to_float().
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The conversion routines are as accurate as the float datatype can
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be. Furthermore, they should handle all special values (NaN, inf, denormalized
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numbers) correctly. There are testcases in test_conversions.c.
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