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#ifndef UTOA_H
#define UTOA_H
#include <stdint.h>
#include <string>
#include <cstring>
#include <limits>
// define this if you're paranoid about converting 0-9 (int) to 0-9 (char) by adding to '0', which is safe for ascii, utf8, etc.
#ifndef DIGIT_LOOKUP_TABLE
# define DIGIT_LOOKUP_TABLE 0
#endif
//TODO: 3 decimal digit lookup table, divide by 1000 faster?
//TODO: benchmark these two (also, some assembly that does effectively divmod?)
#if 1
// maybe this is faster than mod because we are already dividing
#define NDIV10MOD(rem,n) rem = n; n /= 10; rem -= 10*n;
#else
// or maybe optimizer does it just as well or better with this:
#define NDIV10MOD(rem,n) rem = n%10; n = n/10;
#endif
template <class T>
struct signed_for_int {
};
#define DEFINE_SIGNED_FOR_3(t,it,ut) \
template <> \
struct signed_for_int<t> { \
typedef ut unsigned_t; \
typedef it signed_t; \
typedef t original_t; \
enum { toa_bufsize = 3 + std::numeric_limits<t>::digits10, toa_bufsize_minus_1=toa_bufsize-1 }; \
};
// toa_bufsize will hold enough chars for a c string converting to sign,digits (for both signed and unsigned types), because normally an unsigned would only need 2 extra chars. we reserve 3 explicitly for the case that itoa(buf,UINT_MAX,true) is called, with output +4......
#define DEFINE_SIGNED_FOR(it) DEFINE_SIGNED_FOR_3(it,it,u ## it) \
DEFINE_SIGNED_FOR_3(u ## it,it,u ## it)
DEFINE_SIGNED_FOR(int8_t)
DEFINE_SIGNED_FOR(int16_t)
DEFINE_SIGNED_FOR(int32_t)
DEFINE_SIGNED_FOR(int64_t)
//DEFINE_SIGNED_FOR_3(int,int,unsigned)
//DEFINE_SIGNED_FOR_3(unsigned,int,unsigned)
/*
// The largest 32-bit integer is 4294967295, that is 10 chars
// 1 more for sign, and 1 for 0-termination of string
const unsigned utoa_bufsize=12;
const unsigned utoa_bufsizem1=utoa_bufsize-1;
const unsigned ultoa_bufsize=22;
const unsigned ultoa_bufsizem1=utoa_bufsize-1;
*/
#ifdef DIGIT_LOOKUP_TABLE
namespace {
char digits[] = "0123456789";
}
#endif
inline char digit_to_char(int d) {
return
#ifdef DIGIT_LOOKUP_TABLE
digits[d];
#else
'0'+d;
#endif
}
// returns n in string [return,num); *num=0 yourself before calling if you want a c_str. in other words, the sequence [ret,buf) contains the written digits
template <class Int>
char *utoa(char *buf,Int n_) {
typedef typename signed_for_int<Int>::unsigned_t Uint;
Uint n=n_;
if (!n) {
*--buf='0';
} else {
Uint rem;
// 3digit lookup table, divide by 1000 faster?
while (n) {
NDIV10MOD(rem,n);
*--buf = digit_to_char(rem);
}
}
return buf;
}
// left_pad_0(buf,utoa(buf+bufsz,n)) means that [buf,buf+bufsz) is a left-0 padded seq. of digits. no 0s are added if utoa is already past buf (you must have ensured that this is valid memory, naturally)
inline void left_pad(char *left,char *buf,char pad='0') {
while (buf>left)
*--buf=pad;
// return buf;
}
template <class Int>
char *utoa_left_pad(char *buf,char *bufend,Int n, char pad='0') {
char *r=utoa(bufend,n);
assert(buf<=r);
left_pad(buf,r,pad);
return buf;
}
// note: 0 -> 0, but otherwise x000000 -> x (x has no trailing 0s). same conditions as utoa; [ret,buf) gives the sequence of digits
// useful for floating point fraction output
template <class Uint_>
char *utoa_drop_trailing_0(char *buf,Uint_ n_, unsigned &n_skipped) {
typedef typename signed_for_int<Uint_>::unsigned_t Uint;
Uint n=n_;
n_skipped=0;
if (!n) {
*--buf='0';
return buf;
} else {
Uint rem;
while (n) {
NDIV10MOD(rem,n);
if (rem) {
*--buf = digit_to_char(rem);
// some non-0 trailing digits; now output all digits.
while (n) {
NDIV10MOD(rem,n);
*--buf = digit_to_char(rem);
}
return buf;
}
++n_skipped;
}
assert(0);
return 0;
}
}
// desired feature: itoa(unsigned) = utoa(unsigned)
// positive sign: 0 -> +0, 1-> +1. obviously -n -> -n
template <class Int>
//typename signed_for_int<Int>::original_t instead of Int to give more informative wrong-type message?
char *itoa(char *buf,Int i,bool positive_sign=false) {
typename signed_for_int<Int>::unsigned_t n=i;
if (i<0)
n=-n; //sidesteps 2s complement issue doing this rather than just u=-n.
char * ret=utoa(buf,n);
if (i<0) {
*--ret='-';
} else if (positive_sign)
*--ret='+';
return ret;
}
template <class Int>
char * itoa_left_pad(char *buf,char *bufend,Int i,bool positive_sign=false,char pad='0') {
typename signed_for_int<Int>::unsigned_t n=i;
if (i<0) {
n=-n; //sidesteps 2s complement issue doing this rather than just u=-n.
*buf='-';
} else if (positive_sign)
*buf='+';
char * r=utoa(bufend,n);
assert(buf<r);
left_pad(buf+1,r,pad);
return buf;
}
template <class Int>
inline std::string itos(Int n) {
char buf[signed_for_int<Int>::toa_bufsize];
char *end=buf+signed_for_int<Int>::toa_bufsize;
char *p=itoa(end,n);
return std::string(p,end);
}
template <class Int>
inline std::string utos(Int n) {
char buf[signed_for_int<Int>::toa_bufsize];
char *end=buf+signed_for_int<Int>::toa_bufsize;
char *p=itoa(end,n);
return std::string(p,end);
}
//returns position of '\0' terminating number written starting at to
template <class Int>
inline char* append_utoa(char *to,typename signed_for_int<Int>::unsigned_t n) {
char buf[signed_for_int<Int>::toa_bufsize];
char *end=buf+signed_for_int<Int>::toa_bufsize;
char *p=itoa(end,n);
int ns=end-p;
std::memcpy(to,p,ns);
to+=ns;
*to=0;
return to;
}
//returns position of '\0' terminating number written starting at to
template <class Int>
inline char* append_itoa(char *to,typename signed_for_int<Int>::signed_t n) {
char buf[signed_for_int<Int>::toa_bufsize];
char *end=buf+signed_for_int<Int>::toa_bufsize;
char *p=utoa(end,n);
int ns=end-p;
std::memcpy(to,p,ns);
to+=ns;
*to=0;
return to;
}
#endif
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