ubgpsuite/lonetix/include/df/numlib.h

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2021-06-07 16:55:13 +02:00
// SPDX-License-Identifier: LGPL-3.0-or-later
/**
* \file numlib.h
*
* Fast locale independent conversion from numerics (integer or floating point
* types) to ASCII and back.
*
* \copyright The DoubleFourteen Code Forge (C) All Rights Reserved
* \author Lorenzo Cogotti
*/
#ifndef DF_NUMLIB_H_
#define DF_NUMLIB_H_
#include "xpt.h"
/**
* \brief Integral compile-time costant representing an upper-bound estimate
* of the number of digit-characters necessary to hold the **decimal**
* representation of `typ`.
*
* Can be used as such:
* ```c
* char buf[1 + DIGS(int) + 1]; // sign + digits + '\0'
*
* Itoa(INT_MAX, buf);
* ```
*
* Approximation is derived from the following formula, where `MAX_INT` is
* the maximum integral value representable by `typ`:
* ```
* N = ceil(log10(MAX_INT)) ->
* N = floor(log10(MAX_INT)) + 1 ->
* (as base-256 logarithm)
* N = floor( log256(MAX_INT) / log256(10) ) + 1 ->
*
* N <= floor( sizeof(typ) * 2.40824 ) + 1 ->
*
* N ~= 241 * sizeof(typ) / 100 + 1
* ```
*
* \param typ An **integer** type or expression
*
* \author [John Bollinger](https://stackoverflow.com/a/43789115)
*/
#define DIGS(typ) ((241 * sizeof(typ)) / 100 + 1)
// #define DIGS(typ) (sizeof(typ) * CHAR_BIT) gross upper-bound approx
/**
* \brief Integral compile-time constant representing an upper-bound estimate
* of the number of digit-characters necessary to hold the **hexadecimal**
* representation of `typ`.
*
* \param typ An **integer** type or expression
*/
#define XDIGS(typ) (sizeof(typ) * 2)
/**
* \brief Maximum number of characters returned by `Ftoa()`,
* **excluding terminating `\0` char**.
*
* Range of double (IEEE-754 `binary64`): `[1.7E-308 ... 1.7E308]`
* - 1 char for sign
* - 309 digits for integer part
* - 1 char for mantissa dot
* - 37 chars for mantissa
*/
#define DOUBLE_STRLEN (309 + 39)
STATIC_ASSERT(sizeof(double) <= 8, "DOUBLE_STRLEN might be inaccurate on this platform");
// should actually make sure we also have IEEE-754 floats...
/**
* \brief Unsigned integer to ASCII conversion.
*
* Destination buffer is assumed to be large enough to hold the
* result. A storage of `DIGS(x) + 1` chars is guaranteed
* to be sufficient. Resulting string is always `NUL` terminated.
*
* \param [in] x Value to be converted
* \param [out] dest Destination string, must not be `\0`
*
* \return Pointer to the trailing `\0` char inside `dest`, useful
* for further string concatenation.
*/
char *Utoa(unsigned long long x, char *dest);
/**
* \brief Signed integer to ASCII conversion.
*
* Destination buffer is assumed to be large enough to hold the result.
* A storage of `1 + DIGS(x) + 1` chars, accounting for the sign
* character, is guaranteed to be sufficient.
*
* \param [in] x Value to be converted
* \param [out] dest Destination string, must not be `NULL`
*
* \return Pointer to the trailing `\0` char in `dest`, useful for further
* string concatenation.
*/
char *Itoa(long long x, char *dest);
/**
* \brief Unsigned integer to hexadecimal lowercase ASCII string.
*
* Destination buffer is assumed to be large enough to hold the result.
* A storage of `XDIGS(x) + 1` chars is guaranteed to be
* sufficient. Resulting string is always `\0` terminated.
*
* \param [in] x Value to be converted
* \param [out] dest Destination string, must not be `NULL`
*
* \return Pointer to the trailing `\0` char in `dest`, useful for further
* string concatenation.
*
* \note No `0x` prefix is prepended to resulting string.
*/
char *Xtoa(unsigned long long x, char *dest);
/**
* \brief Floating point number to scientific notation string.
*
* Destination string is assumed to be large enough to store the conversion
* result, a buffer of size `DOUBLE_STRLEN + 1` is guaranteed to be large
* enough for it. Result is always `\0` terminated.
*
* \param [in] x Floating point number to be converted
* \param [out] dest Destination for result string, must not be `NULL`
*
* \return Pointer to the trailing `\0` char inside result, useful for
* further string concatenation.
*/
char *Ftoa(double x, char *dest);
/// Numeric conversion outcomes.
typedef enum {
NCVENOERR = 0, ///< Conversion successful
NCVEBADBASE, ///< The specified numeric base is out of range
NCVENOTHING, ///< No legal numeric data in input string
NCVEOVERFLOW, ///< Numeric input too large for target integer type
NCVEUNDERFLOW ///< Numeric input too small for target integer type
} NumConvRet;
/**
* \brief ASCII to integer conversion.
*
* If `base` is 0 then the actual numeric base is guessed from input string
* prefix according to an extended C convention:
*
* Numeric prefix | Base
* ---------------|---------------------
* __0__ | octal, base 8
* __0x__ | hexadecimal, base 16
* __0b__ | binary, base 2
* __otherwise__ | decimal, base 10
*
* \param [in] s Input string to be converted, must not be `NULL`
* \param [out] endp Storage where end pointer is returned, may be `NULL`
* \param [in] base Integer conversion base, a value between 0 and 36 inclusive
* \param [out] outcome Storage where conversion outcome is returned, may be `NULL`
*
* \return Conversion result, 0 on error (use `outcome` to detect error).
*
* @{
* \fn unsigned long long Atoull(const char *, char **, unsigned, NumConvRet *)
* \fn unsigned long Atoul(const char *, char **, unsigned, NumConvRet *)
* \fn unsigned Atou(const char *, char **, unsigned, NumConvRet *)
* \fn long long Atoll(const char *, char **, unsigned, NumConvRet *)
* \fn long Atol(const char *, char **, unsigned, NumConvRet *)
* \fn int Atoi(const char *, char **, unsigned, NumConvRet *)
* @}
*/
unsigned long long Atoull(const char *s, char **endp, unsigned base, NumConvRet *outcome);
unsigned long Atoul(const char *s, char **endp, unsigned base, NumConvRet *outcome);
unsigned Atou(const char *s, char **endp, unsigned base, NumConvRet *outcome);
long long Atoll(const char *s, char **endp, unsigned base, NumConvRet *outcome);
long Atol(const char *s, char **endp, unsigned base, NumConvRet *outcome);
int Atoi(const char *s, char **endp, unsigned base, NumConvRet *outcome);
/**
* \brief ASCII to floating point conversion.
*
* \param [in] s Input string to be converted, must not be `NULL`
* \param [out] endp Storage where end pointer is returned, must not be `NULL`
* \param [out] outcome Storage where conversion outcome is returned, may be `NULL`
*
* \return Conversion result, 0 on error (use `outcome` to detect error).
*/
double Atof(const char *s, char **endp, NumConvRet *outcome);
#endif