github.com/afumu/libc@v0.0.6/musl/src/stdlib/fcvt.c (about)

     1  #define _GNU_SOURCE
     2  #include <stdlib.h>
     3  #include <stdio.h>
     4  #include <string.h>
     5  
     6  char *fcvt(double x, int n, int *dp, int *sign)
     7  {
     8  	char tmp[1500];
     9  	int i, lz;
    10  
    11  	if (n > 1400U) n = 1400;
    12  	sprintf(tmp, "%.*f", n, x);
    13  	i = (tmp[0] == '-');
    14  	if (tmp[i] == '0') lz = strspn(tmp+i+2, "0");
    15  	else lz = -(int)strcspn(tmp+i, ".");
    16  
    17  	if (n<=lz) {
    18  		*sign = i;
    19  		*dp = 1;
    20  		if (n>14U) n = 14;
    21  		return "000000000000000"+14-n;
    22  	}
    23  
    24  	return ecvt(x, n-lz, dp, sign);
    25  }