src/std_dtoa.h

/*
 * Copyright (c) 2019, The Linux Foundation. All rights reserved.
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 * modification, are permitted provided that the following conditions are
 * met:
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 *      notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer in the documentation and/or other materials provided
 *      with the distribution.
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 *      from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
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 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
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 */

#ifndef STD_DTOA_H
#define STD_DTOA_H

//
// Constant Definitions
//

// For floating point numbers, the range of a double precision number is
// approximately +/- 10 ^ 308.25 as per the IEEE Standard 754.
// As such, the maximum size of the integer portion of the
// string is assumed to be 311 (309 + sign + \0). The maximum
// size of the fractional part is assumed to be 100. Thus, the
// maximum size of the string that would contain the number
// after conversion is safely assumed to be 420 (including any
// prefix, the null character and exponent specifiers 'e').
//
// The buffers that contain the converted integer and the fraction parts of
// the float are safely assumed to be of size 310.
#define STD_DTOA_FORMAT_FLOAT_SIZE           420
#define STD_DTOA_FORMAT_INTEGER_SIZE         311
#define STD_DTOA_FORMAT_FRACTION_SIZE        100

// Constants for operations on the IEEE 754 representation of double
// precision floating point numbers.
#define STD_DTOA_DP_SIGN_SHIFT_COUNT         63
#define STD_DTOA_DP_EXPONENT_SHIFT_COUNT     52
#define STD_DTOA_DP_EXPONENT_MASK            0x7ff
#define STD_DTOA_DP_EXPONENT_BIAS            1023
#define STD_DTOA_DP_MANTISSA_MASK            ( ( (uint64)1 << 52 ) - 1 )
#define STD_DTOA_DP_INFINITY_EXPONENT_ID     0x7FF
#define STD_DTOA_DP_MAX_EXPONENT             1023
#define STD_DTOA_DP_MIN_EXPONENT_NORM        -1022
#define STD_DTOA_DP_MIN_EXPONENT_DENORM      -1074
#define STD_DTOA_DP_MAX_EXPONENT_DEC         308
#define STD_DTOA_DP_MIN_EXPONENT_DEC_DENORM  -323

#define STD_DTOA_PRECISION_ROUNDING_VALUE    4
#define STD_DTOA_DEFAULT_FLOAT_PRECISION     6

#define STD_DTOA_NEGATIVE_INF_UPPER_CASE     "-INF"
#define STD_DTOA_NEGATIVE_INF_LOWER_CASE     "-inf"
#define STD_DTOA_POSITIVE_INF_UPPER_CASE     "INF"
#define STD_DTOA_POSITIVE_INF_LOWER_CASE     "inf"
#define STD_DTOA_NAN_UPPER_CASE              "NAN"
#define STD_DTOA_NAN_LOWER_CASE              "nan"
#define STD_DTOA_FP_POSITIVE_INF             0x7FF0000000000000uLL
#define STD_DTOA_FP_NEGATIVE_INF             0xFFF0000000000000uLL
#define STD_DTOA_FP_SNAN                     0xFFF0000000000001uLL
#define STD_DTOA_FP_QNAN                     0xFFFFFFFFFFFFFFFFuLL

//
// Useful Macros
//

#define MY_ISDIGIT(c)            ( ( (c) >= '0' ) && ( (c) <= '9' ) )
#define FP_EXPONENT(u)           ( ( ( (u) >> STD_DTOA_DP_EXPONENT_SHIFT_COUNT ) \
                                    & STD_DTOA_DP_EXPONENT_MASK ) - STD_DTOA_DP_EXPONENT_BIAS )
#define FP_EXPONENT_BIASED(u)    ( ( (u) >> STD_DTOA_DP_EXPONENT_SHIFT_COUNT ) \
                                    & STD_DTOA_DP_EXPONENT_MASK )
#define FP_MANTISSA_NORM(u)      ( ( (u) & STD_DTOA_DP_MANTISSA_MASK ) | \
                                    ( (uint64)1 << STD_DTOA_DP_EXPONENT_SHIFT_COUNT ) )
#define FP_MANTISSA_DENORM(u)    ( (u) & STD_DTOA_DP_MANTISSA_MASK )
#define FP_MANTISSA(u)           ( FP_EXPONENT_BIASED(u) ? FP_MANTISSA_NORM(u) : \
                                    FP_MANTISSA_DENORM(u) )
#define FP_SIGN(u)               ( (u) >> STD_DTOA_DP_SIGN_SHIFT_COUNT )
#define DOUBLE_TO_UINT64(d)      ( *( (uint64*) &(d) ) )
#define DOUBLE_TO_INT64(d)       ( *( (int64*) &(d) ) )
#define UINT64_TO_DOUBLE(u)      ( *( (double*) &(u) ) )

//
// Type Definitions
//

typedef enum
{
   FP_TYPE_UNKOWN = 0,
   FP_TYPE_NEGATIVE_INF,
   FP_TYPE_POSITIVE_INF,
   FP_TYPE_NAN,
   FP_TYPE_GENERAL,
} FloatingPointType;

//
// Function Declarations
//

#ifdef __cplusplus
extern "C" {
#endif // #ifdef __cplusplus

double fp_pow_10( int nPow );
double fp_round( double dNumber, int nPrecision );
int fp_log_10( double dNumber );
int fp_check_special_cases( double dNumber, FloatingPointType* pNumberType );
int std_dtoa_decimal( double dNumber, int nPrecision,
                      char acIntegerPart[ STD_DTOA_FORMAT_INTEGER_SIZE ],
                      char acFractionPart[ STD_DTOA_FORMAT_FRACTION_SIZE ] );
int std_dtoa_hex( double dNumber, int nPrecision, char cFormat,
                  char acIntegerPart[ STD_DTOA_FORMAT_INTEGER_SIZE ],
                  char acFractionPart[ STD_DTOA_FORMAT_FRACTION_SIZE ],
                  int* pnExponent );

#ifdef __cplusplus
}
#endif // #ifdef __cplusplus

#endif   // STD_DTOA_H