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