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[apps/graph/values] Add a parameter in float_to_string to cap the number of significative number

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Change-Id: I8406a910c176da13147fe0235b183ea22dc4faa0
This commit is contained in:
Émilie Feral
2016-10-11 11:42:37 +02:00
parent 2aa227ce0f
commit 2b8df283e2
4 changed files with 29 additions and 14 deletions
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37
apps/graph/values/float_to_string.cpp
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@@ -25,10 +25,12 @@ void FloatToString::printBase10IntegerWithDecimalMarker(char * buffer, int buffe
} while (endChar >= startChar);
}
void FloatToString::convertFloatToText(float f, char * buffer, int maxNumberOfChar, Mode mode) {
/* We here assert that the buffer is long enough to display any float in a
* understandable way: the worst case has the form -1e-38 (6+1 char). */
assert(maxNumberOfChar > 6);
void FloatToString::convertFloatToText(float f, char * buffer, int maxNumberOfChar,
int numberOfDigitsInMantissa, Mode mode) {
/* We here assert that the buffer is long enough to display with the right
* number of digits in the mantissa. If numberOfDigitsInMantissa = 7, the
* worst case has the form -1.999999e-38 (7+6+1 char). */
assert(maxNumberOfChar > 6 + numberOfDigitsInMantissa);
//if (isinf(f)) {
float maximalFloat = 3.4f*powf(10, 38);
@@ -59,19 +61,32 @@ void FloatToString::convertFloatToText(float f, char * buffer, int maxNumberOfCh
* decide whether to display the exponent. */
// Number of char available for the mantissa
int availableCharsForMantissa = maxNumberOfChar - numberOfCharExponent - 2;
int availableCharsForMantissaWithoutSign = numberOfDigitsInMantissa + 1;
int availableCharsForMantissaWithSign = f >= 0 ? availableCharsForMantissaWithoutSign : availableCharsForMantissaWithoutSign + 1;
// Compute mantissa
/* The number of digits in an integer is capped because the maximal integer is
* 2^31 - 1. As our mantissa is an integer, we assert that we stay beyond this
* threshold during computation. */
int numberMaximalOfCharsInInteger = log10f(powf(2, 31));
assert(availableCharsForMantissa < numberMaximalOfCharsInInteger);
int mantissa = f >= 0 ? f * powf(10, availableCharsForMantissa - exponentInBase10 - 2) : f * powf(10, availableCharsForMantissa - exponentInBase10 - 3);
assert(availableCharsForMantissaWithoutSign - 1 < numberMaximalOfCharsInInteger);
int mantissa = f * powf(10, availableCharsForMantissaWithoutSign - exponentInBase10 - 2);
// Supress the 0 on the right side of the mantissa
int dividend = fabsf((float)mantissa);
int quotien = dividend/10;
int digit = dividend - quotien*10;
while (digit == 0 && availableCharsForMantissaWithSign > 2) {
mantissa = mantissa/10;
availableCharsForMantissaWithSign--;
dividend = quotien;
quotien = dividend/10;
digit = dividend - quotien*10;
}
// Print sequentially mantissa and exponent
printBase10IntegerWithDecimalMarker(buffer, availableCharsForMantissa, mantissa, 1);
buffer[availableCharsForMantissa] = 'e';
printBase10IntegerWithDecimalMarker(buffer+availableCharsForMantissa+1, numberOfCharExponent, exponentInBase10, -1);
buffer[availableCharsForMantissa+1+numberOfCharExponent] = 0;
printBase10IntegerWithDecimalMarker(buffer, availableCharsForMantissaWithSign, mantissa, 1);
buffer[availableCharsForMantissaWithSign] = 'e';
printBase10IntegerWithDecimalMarker(buffer+availableCharsForMantissaWithSign+1, numberOfCharExponent, exponentInBase10, -1);
buffer[availableCharsForMantissaWithSign+1+numberOfCharExponent] = 0;
}