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author | 2017-05-02 17:51:53 +0200 | |
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committer | 2017-05-02 17:51:53 +0200 | |
commit | 3102ec9ce009d0f28355c5b7df9c5bd5013e6e75 (patch) | |
tree | 80a1ea19ff06cc9308b236a0d8d6358d21dd0381 /CAN-binder/libs/nanopb/examples/using_double_on_avr/double_conversion.c | |
parent | 12e680a3c97a2750c657a8c561a79706f3689149 (diff) | |
parent | 278ffb890e3d8722e4c7d824baaf221a1e375fc4 (diff) |
Add 'CAN-binder/libs/nanopb/' from commit '278ffb890e3d8722e4c7d824baaf221a1e375fc4'
git-subtree-dir: CAN-binder/libs/nanopb
git-subtree-mainline: 12e680a3c97a2750c657a8c561a79706f3689149
git-subtree-split: 278ffb890e3d8722e4c7d824baaf221a1e375fc4
Diffstat (limited to 'CAN-binder/libs/nanopb/examples/using_double_on_avr/double_conversion.c')
-rw-r--r-- | CAN-binder/libs/nanopb/examples/using_double_on_avr/double_conversion.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/CAN-binder/libs/nanopb/examples/using_double_on_avr/double_conversion.c b/CAN-binder/libs/nanopb/examples/using_double_on_avr/double_conversion.c new file mode 100644 index 00000000..cf79b9a0 --- /dev/null +++ b/CAN-binder/libs/nanopb/examples/using_double_on_avr/double_conversion.c @@ -0,0 +1,123 @@ +/* Conversion routines for platforms that do not support 'double' directly. */ + +#include "double_conversion.h" +#include <math.h> + +typedef union { + float f; + uint32_t i; +} conversion_t; + +/* Note: IEE 754 standard specifies float formats as follows: + * Single precision: sign, 8-bit exp, 23-bit frac. + * Double precision: sign, 11-bit exp, 52-bit frac. + */ + +uint64_t float_to_double(float value) +{ + conversion_t in; + in.f = value; + uint8_t sign; + int16_t exponent; + uint64_t mantissa; + + /* Decompose input value */ + sign = (in.i >> 31) & 1; + exponent = ((in.i >> 23) & 0xFF) - 127; + mantissa = in.i & 0x7FFFFF; + + if (exponent == 128) + { + /* Special value (NaN etc.) */ + exponent = 1024; + } + else if (exponent == -127) + { + if (!mantissa) + { + /* Zero */ + exponent = -1023; + } + else + { + /* Denormalized */ + mantissa <<= 1; + while (!(mantissa & 0x800000)) + { + mantissa <<= 1; + exponent--; + } + mantissa &= 0x7FFFFF; + } + } + + /* Combine fields */ + mantissa <<= 29; + mantissa |= (uint64_t)(exponent + 1023) << 52; + mantissa |= (uint64_t)sign << 63; + + return mantissa; +} + +float double_to_float(uint64_t value) +{ + uint8_t sign; + int16_t exponent; + uint32_t mantissa; + conversion_t out; + + /* Decompose input value */ + sign = (value >> 63) & 1; + exponent = ((value >> 52) & 0x7FF) - 1023; + mantissa = (value >> 28) & 0xFFFFFF; /* Highest 24 bits */ + + /* Figure if value is in range representable by floats. */ + if (exponent == 1024) + { + /* Special value */ + exponent = 128; + } + else if (exponent > 127) + { + /* Too large */ + if (sign) + return -INFINITY; + else + return INFINITY; + } + else if (exponent < -150) + { + /* Too small */ + if (sign) + return -0.0f; + else + return 0.0f; + } + else if (exponent < -126) + { + /* Denormalized */ + mantissa |= 0x1000000; + mantissa >>= (-126 - exponent); + exponent = -127; + } + + /* Round off mantissa */ + mantissa = (mantissa + 1) >> 1; + + /* Check if mantissa went over 2.0 */ + if (mantissa & 0x800000) + { + exponent += 1; + mantissa &= 0x7FFFFF; + mantissa >>= 1; + } + + /* Combine fields */ + out.i = mantissa; + out.i |= (uint32_t)(exponent + 127) << 23; + out.i |= (uint32_t)sign << 31; + + return out.f; +} + + |