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Shrink knx code size by 5k using local pow

This commit is contained in:
Theo Arends 2020-05-15 14:07:16 +02:00
parent b9a4e7beda
commit 6573802f83
1 changed files with 25 additions and 1 deletions
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26
lib/esp-knx-ip-0.5.2/esp-knx-ip-conversion.cpp
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@ -35,12 +35,36 @@ uint16_t ESPKNXIP::data_to_2byte_uint(uint8_t *data)
return (uint16_t)((data[1] << 8) | data[2]);
}
float esp_knx_pow(float a, float b)
{
// https://martin.ankerl.com/2012/01/25/optimized-approximative-pow-in-c-and-cpp/
// calculate approximation with fraction of the exponent
int e = abs((int)b);
union {
double d;
int x[2];
} u = { a };
u.x[1] = (int)((b - e) * (u.x[1] - 1072632447) + 1072632447);
u.x[0] = 0;
// exponentiation by squaring with the exponent's integer part
// double r = u.d makes everything much slower, not sure why
double r = 1.0;
while (e) {
if (e & 1) {
r *= a;
}
a *= a;
e >>= 1;
}
return r * u.d;
}
float ESPKNXIP::data_to_2byte_float(uint8_t *data)
{
//uint8_t sign = (data[1] & 0b10000000) >> 7;
uint8_t expo = (data[1] & 0b01111000) >> 3;
int16_t mant = ((data[1] & 0b10000111) << 8) | data[2];
return 0.01f * mant * pow(2, expo);
return 0.01f * mant * esp_knx_pow(2, expo);
}
time_of_day_t ESPKNXIP::data_to_3byte_time(uint8_t *data)