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author | Etan Cohen <etancohen@google.com> | 2014-08-20 10:11:11 -0700 |
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committer | Etan Cohen <etancohen@google.com> | 2014-08-20 10:11:11 -0700 |
commit | 7ef855e462b9a18b7d330e4b40f350164a6ad9da (patch) | |
tree | a43d91fcc4567b75966b901f2c1dbe7581a930e0 /examples/using_double_on_avr/double_conversion.c | |
parent | 430f996db620d94da8042d70c61e137175687693 (diff) | |
download | nanopb-c-android-5.1.1_r38.tar.gz |
Initial check-in of nanopb-c.android-wear-5.1.1_r1android-wear-5.1.0_r1android-wear-5.0.0_r1android-cts-5.1_r9android-cts-5.1_r8android-cts-5.1_r7android-cts-5.1_r6android-cts-5.1_r5android-cts-5.1_r4android-cts-5.1_r3android-cts-5.1_r28android-cts-5.1_r27android-cts-5.1_r26android-cts-5.1_r25android-cts-5.1_r24android-cts-5.1_r23android-cts-5.1_r22android-cts-5.1_r21android-cts-5.1_r20android-cts-5.1_r2android-cts-5.1_r19android-cts-5.1_r18android-cts-5.1_r17android-cts-5.1_r16android-cts-5.1_r15android-cts-5.1_r14android-cts-5.1_r13android-cts-5.1_r10android-cts-5.1_r1android-cts-5.0_r9android-cts-5.0_r8android-cts-5.0_r7android-cts-5.0_r6android-cts-5.0_r5android-cts-5.0_r4android-cts-5.0_r3android-5.1.1_r9android-5.1.1_r8android-5.1.1_r7android-5.1.1_r6android-5.1.1_r5android-5.1.1_r4android-5.1.1_r38android-5.1.1_r37android-5.1.1_r36android-5.1.1_r35android-5.1.1_r34android-5.1.1_r33android-5.1.1_r30android-5.1.1_r3android-5.1.1_r29android-5.1.1_r28android-5.1.1_r26android-5.1.1_r25android-5.1.1_r24android-5.1.1_r23android-5.1.1_r22android-5.1.1_r20android-5.1.1_r2android-5.1.1_r19android-5.1.1_r18android-5.1.1_r17android-5.1.1_r16android-5.1.1_r15android-5.1.1_r14android-5.1.1_r13android-5.1.1_r12android-5.1.1_r10android-5.1.1_r1android-5.1.0_r5android-5.1.0_r4android-5.1.0_r3android-5.1.0_r1android-5.0.2_r3android-5.0.2_r1android-5.0.1_r1android-5.0.0_r7android-5.0.0_r6android-5.0.0_r5.1android-5.0.0_r5android-5.0.0_r4android-5.0.0_r3android-5.0.0_r2android-5.0.0_r1master-soonglollipop-wear-releaselollipop-releaselollipop-mr1-wfc-releaselollipop-mr1-releaselollipop-mr1-fi-releaselollipop-mr1-devlollipop-mr1-cts-releaselollipop-devlollipop-cts-release
Copied from klp-wireless-dev.
Change-Id: I7055708554a8a818edba8ce1da35d589b76c1621
Diffstat (limited to 'examples/using_double_on_avr/double_conversion.c')
-rw-r--r-- | examples/using_double_on_avr/double_conversion.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/examples/using_double_on_avr/double_conversion.c b/examples/using_double_on_avr/double_conversion.c new file mode 100644 index 0000000..cf79b9a --- /dev/null +++ b/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; +} + + |