c - Convert double/float to string

Question

I need to convert a floating point number to an equivalent string in decimal (or other base). Conversion at first needs to be done in the format xE+0 where x is the floating point number.

The idea I have is to first truncate the floating point number into a temporary integer and then convert that integer into string, and then consider the fractional part, multiply it with 10 while the fractional part does not become 0. After the fractional part is transferred into the left side of the decimal point, apply the integer to string function again and convert the fraction part to string. Is there a better way, which will be faster than this? Will this method induce any kind of side effects?

To convert the floating point number into exponential representation shall I do the same as above and then adjust the power? Or directly bitmask the IEEE 754 floating point representation and convert each part into string.

Note: No other functions could be used, because I have access to absolutely no library functions. This code goes into a toy kernel.

Answer 1

Use snprintf() from stdlib.h. Worked for me.

double num = 123412341234.123456789; 
char output[50];

snprintf(output, 50, "%f", num);

printf("%s", output);