int_to_str.c

void reverse_bytes(char* restrict bytes, const size_t len){
    for(size_t i=0;i<len/2;i++){
        char tmp=bytes[i];
        bytes[i]=bytes[len-1-i];
        bytes[len-1-i]=tmp;
    }
}

// str must have 11 bytes allocated to it
void int_to_str(int val, char* str){
    if(val<0)val=-val,*str++='-';
    size_t i=0;
    while(val){
        char c=val%10;
        str[i++]=c+'0';
        val-=c,val/=10;
    }
    str[i]=0;
    reverse_bytes(str, i);
}