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/*---------------------------------------------------------------------------
*
* Common routines for Ryu floating-point output.
*
* Portions Copyright (c) 2018-2022, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/common/ryu_common.h
*
* This is a modification of code taken from github.com/ulfjack/ryu under the
* terms of the Boost license (not the Apache license). The original copyright
* notice follows:
*
* Copyright 2018 Ulf Adams
*
* The contents of this file may be used under the terms of the Apache
* License, Version 2.0.
*
* (See accompanying file LICENSE-Apache or copy at
* http://www.apache.org/licenses/LICENSE-2.0)
*
* Alternatively, the contents of this file may be used under the terms of the
* Boost Software License, Version 1.0.
*
* (See accompanying file LICENSE-Boost or copy at
* https://www.boost.org/LICENSE_1_0.txt)
*
* Unless required by applicable law or agreed to in writing, this software is
* distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.
*
*---------------------------------------------------------------------------
*/
#ifndef RYU_COMMON_H
#define RYU_COMMON_H
/*
* Upstream Ryu's output is always the shortest possible. But we adjust that
* slightly to improve portability: we avoid outputting the exact midpoint
* value between two representable floats, since that relies on the reader
* getting the round-to-even rule correct, which seems to be the common
* failure mode.
*
* Defining this to 1 would restore the upstream behavior.
*/
#define STRICTLY_SHORTEST 0
#if SIZEOF_SIZE_T < 8
#define RYU_32_BIT_PLATFORM
#endif
/* Returns e == 0 ? 1 : ceil(log_2(5^e)). */
static inline uint32
pow5bits(const int32 e)
{
/*
* This approximation works up to the point that the multiplication
* overflows at e = 3529.
*
* If the multiplication were done in 64 bits, it would fail at 5^4004
* which is just greater than 2^9297.
*/
Assert(e >= 0);
Assert(e <= 3528);
return ((((uint32) e) * 1217359) >> 19) + 1;
}
/* Returns floor(log_10(2^e)). */
static inline int32
log10Pow2(const int32 e)
{
/*
* The first value this approximation fails for is 2^1651 which is just
* greater than 10^297.
*/
Assert(e >= 0);
Assert(e <= 1650);
return (int32) ((((uint32) e) * 78913) >> 18);
}
/* Returns floor(log_10(5^e)). */
static inline int32
log10Pow5(const int32 e)
{
/*
* The first value this approximation fails for is 5^2621 which is just
* greater than 10^1832.
*/
Assert(e >= 0);
Assert(e <= 2620);
return (int32) ((((uint32) e) * 732923) >> 20);
}
static inline int
copy_special_str(char *const result, const bool sign, const bool exponent, const bool mantissa)
{
if (mantissa)
{
memcpy(result, "NaN", 3);
return 3;
}
if (sign)
{
result[0] = '-';
}
if (exponent)
{
memcpy(result + sign, "Infinity", 8);
return sign + 8;
}
result[sign] = '0';
return sign + 1;
}
static inline uint32
float_to_bits(const float f)
{
uint32 bits = 0;
memcpy(&bits, &f, sizeof(float));
return bits;
}
static inline uint64
double_to_bits(const double d)
{
uint64 bits = 0;
memcpy(&bits, &d, sizeof(double));
return bits;
}
#endif /* RYU_COMMON_H */
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