Converting double to char* in C++ with high performance

Question

My application needs to convert double values to char* to write to a pipe that accepts only characters. The usual ways of doing this are using the sprintf() functio

Answer 1

/*

_ecvt_s Converts a double number to a string.

Syntax:

errno_t _ecvt_s( 
   char * _Buffer,
   size_t _SizeInBytes,
   double _Value,
   int _Count,
   int *_Dec,
   int *_Sign
);

[out] _Buffer
Filled with the pointer to the string of digits, the result of the conversion.

[in] _SizeInBytes
Size of the buffer in bytes.

[in] _Value
Number to be converted.

[in] _Count
Number of digits stored.

[out] _Dec
Stored decimal-point position.

[out] _Sign
Sign of the converted number.


*/


#include <stdio.h>
#include <stdlib.h>
#include <errno.h>

...
char *buf = (char*) malloc(_CVTBUFSIZE);
int decimal;
int sign;
int err;


err = _ecvt_s(buf, _CVTBUFSIZE, 1.2, 5, &decimal, &sign);

if (err != 0) {
// implement error handling
}
else printf("Converted value: %s\n", buf);

...

Hope this helps.

Answer 2

Are you in control of both ends of the pipe? Are you just trying to tunnel doubles through or do you need a valid text representation of the double?

If you are just tunneling and the pipe is 8 bit clean then use one of the answers above.

If you need a string use one of the other answers above.

If your problem is that the pipe is only 7 bits wide, then convert to radix 64 on write and back again on read.